The Encyclopedia Of Nutrition And Good Health - S pdf

Typically, safflower oil contains 74 percent to 77 percent LINOLEIC ACID, an essential polyunsaturated fatty acid; 16.4 percent OLEIC ACID, a monounsaturated fatty acid; and 6.6 percent

saccharin One of the oldest ARTIFICIAL SWEETEN

-ERS, saccharin has been available for more than 100

years It is not metabolized in humans and it

pro-vides no calories Although saccharin is 300 to 700

times sweeter than TABLE SUGAR, it is often

per-ceived to have a bitter or “metallic” aftertaste at

high concentrations Saccharin is generally

com-bined with a sugar, DEXTROSE, or with ASPARTAME,

another artificial sweetener, for tabletop

sweeten-ers The compound is stable to baking and acidic

conditions; this versatility contributes to its use in

many products, including baked foods, salad

dress-ings, reduced calorie jams, toothpaste, mouthwash,

and other personal care products Saccharin can be

added to chewing gum where it is used with SOR

-BITOL, a sweet sugar analog

In May 2000 officials at the National Institute of

Environmental Health Sciences and its subdivision,

the National Toxicology Program, announced that

saccharin would no longer appear on their list of

“cancer threats.” Saccharin had officially been

listed as a carcinogen in March 1977 when

Cana-dian researchers discovered a link between

saccha-rin and bladder tumors in male rats This finding

immediately triggered the threat of the DELANEY

CLAUSE, a congressionally mandated provision that

requires the U.S Food and Drug Administration to

ban any synthetic food chemical shown to cause

cancer when ingested by laboratory animals When

millions of dieting Americans heard that the only

low-calorie sweetener available was going to be

banned (cyclamates had been banned in 1970 for

similar reasons), they were upset; Congress

responded by protecting saccharin from the

Delaney Clause by allowing it back on the market

with a health warning label Saccharin’s chances

were further damaged in 1981 when the National

Toxicology Program, referring again to the

Cana-dian rat study, decided to put saccharin on its cer causing” list—formally declaring it an “antici-pated human carcinogen.”

“can-In September 1996 the Calorie Control Council,

a trade group of the diet food industry, petitionedthe toxicology program to have saccharin reclassi-fied Subsequently, two government scientific pan-els that looked at the possible link betweensaccharin and cancer supported removal, sayingthat any link to cancer was weak A third scientificpanel of nongovernment experts voted 4–3 againsttaking saccharin off the list

Nevertheless, in December 2000 Congress passedthe Saccharin Warning Elimination via Environ-mental Testing Employing Science and TechnologyAct (“SWEETEST Act”) after a National ToxicologyProgram review concluded that saccharin poses nohealth hazard to humans The report concludedthat the observed bladder tumors in rats werecaused by mechanisms not relevant to humans andthat no data in humans suggest that a carcinogenichazard exists The legislation allowed manufactur-ers to remove the warning labels from saccharinpackages that said the sweetener had been shown

to cause cancer in lab animals (See also FOOD ADDI TIVES; NATURAL SWEETENERS.)

-S-adenosylmethionine (SAMe) A synthetic form

of the AMINO ACID METHIONINE, ine is found in every cell in the human body SAMe has been used in Europe since the 1960s as

S-adenosylmethion-a prescription S-adenosylmethion-antidepressS-adenosylmethion-ant S-adenosylmethion-and pS-adenosylmethion-ain reliever S-adenosylmethion-andwas introduced to the U.S market in 1999 as adietary supplement

In the body SAMe normally maintains cellmembranes and is involved in methylation, aprocess that, among other things, helps to regulatelevels of the mood-lifting neurotransmitters sero-

S

565

tonin and dopamine Some study subjects have

reported that SAMe is effective as an

antidepres-sant Several clinical studies have demonstrated

that SAMe is better than placebo and is equivalent

to nonsteroidal anti-inflammatory drugs (NSAIDS)

such as ibuprofen for easing pain associated with

osteoarthritis Patients suffering from fibromyalgia

have also reported significant relief from the

symp-toms that accompany that disease SAMe has also

shown some promise in treating patients who

suf-fer liver diseases such as cirrhosis (liver failure)

caused by alcohol abuse

Because SAMe was introduced in the United

States as a dietary supplement, it has not

under-gone review by the U.S FDAfor safety or efficacy,

and many scientists and others in the medical

com-munity have expressed skepticism regarding its

reported health benefits These critics say the study

subjects may have been reporting PLACEBO effects

and that all the studies that have been done so far

were for periods of time that were too short to

pro-duce statistically significant results Additional

studies are ongoing Safety data are inadequate for

pregnant and breast-feeding women

Soekin, A L “Abstract: Safety and Efficacy of

S-adeno-sylmethionine (SAMe) for Osteoarthritis,” Journal of

Family Practice 51, no 5 (2002): 425–430.

safflower (Carthamus tinctorius) A thistle-like

plant that produces oil-rich seeds resembling small

sunflower seeds Safflower is a late arrival in the

United States, becoming an established crop only

in the 1950s and 1960s as POLYUNSATURATED VEG

-ETABLE OILS gained in popularity in response to

fears about CHOLESTEROL and SATURATED FAT and

their link to ATHEROSCLEROSIS Varieties of

saf-flower yielding 50 percent oil have been

devel-oped Safflower is cultivated in California and

Montana

Safflower oil contains the highest percentage of

polyunsaturated FATTY ACIDS and the lowest

per-centage of saturated fatty acids among

commer-cially available oils Typically, safflower oil contains

74 percent to 77 percent LINOLEIC ACID, an essential

polyunsaturated fatty acid; 16.4 percent OLEIC ACID,

a monounsaturated fatty acid; and 6.6 percent

sat-urated fatty acids Like SOYBEAN oil, it has a high

smoke point (440° to 480° F) and is often used in

deep-fat frying and sauteeing Safflower oil is rich

in VITAMIN E As a polyunsaturated oil, it is tible to RANCIDITY (decomposition) when heated.These oils should not be reheated

suscep-Like all commercial polyunsaturated cookingoils, safflower is partially hydrogenated to reduceits susceptibility to oxidation and decrease the rate

of rancidity Hydrogenation refers to the chemicalhardening process that adds hydrogen atoms anddecreases the level of saturation Hydrogenated safflower oil yields MARGARINE, VEGETABLE SHORTEN-ING, MAYONNAISE, and other products Hydrogena-tion creates TRANSFATTY ACIDS The safety of theseunusual products has been questioned

The consumption of polyunsaturated vegetableoils like safflower oil can lower the level of LOW-DENSITY LIPOPROTEIN(LDL), the less desirable form

of cholesterol, but at the same time a high intakecan lower the level of HIGH-DENSITY LIPOPROTEIN(HDL), the desirable form of cholesterol (See alsoESSENTIAL FATTY ACIDS.)

saffron (Crocus sativus) This small crocus duces flowers with intense yellow-orange fila-ments When dried, the stamens yield a pungentspice and brilliant yellow coloring agent Saffron

pro-is used for rice dpro-ishes, soup, and sauces, as well

as certain meat dishes in Indian, Italian, and ish cuisine Saffron is best dissolved in a smallamount of warm water before use for uniformmixing (See also FOOD ADDITIVES; FOOD COLORING,NATURAL.)

Span-sage (Salvia officinalis) A common perennialHERB whose fresh or dried leaves add a pungent,bitter taste to foods There are over 500 varieties ofsage, including the common garden sage It is used

to flavor poultry, fatty meat like pork, veal, ham, orlamb, and in marinades, minestrone, and sauces.Sage has long been used as a medicinal herb in folk

medicine Its name comes from the Latin salvus,

which means healthy It possesses bacterial andantifungal properties and it has been used to aiddigestion Sage tea has been used to reduce cough-ing associated with colds and for irregular men-struation As with any medicinal herb, theconsumption of large amounts for long periods oftime is not recommended (See also PARSLEY.)

566 safflower

sago Starch from the trunk of a tropical palm In

the South Pacific, sago palm flour and starch are

staple foods They are used as food thickeners

Commercially, sago starch is used as a noncorn

source of glucose from which to manufacture

corn-free VITAMIN Cfor certain individuals who are

ultra-sensitive to corn products (See also OIL PALM; PALM

OILS.)

salami A deli sausage usually made from PORK

or a combination of pork and BEEF and several

seasonings, including salt, garlic, black pepper,

and fennel Salami is a high-fat (generally 30

per-cent) and high-sodium food Some, but not all,

salamis are cured and may contain preservatives

such as nitrites Several varieties are available,

including cacciatore, pepperoni, and genoa

Salami is usually sliced thin for use in sandwiches

or, in the case of pepperoni, on pizza One slice of

cooked salami (23 g) yields 57.5 calories; fat, 4.5

g; protein, 3 g; potassium, 45.5 mg; sodium 245

mg

saliva The fluid secreted by glands of the MOUTH

Three pairs of salivary glands produce saliva

Parotid glands, located on each side of the face,

drain through ducts opening in the inner surface of

the cheek Sublingual glands drain into the floor of

the mouth Submaxillary glands (submandibular

glands) are located beneath the base of the tongue

and drain in the floor of the mouth Tiny buccal

glands in the mouth also contribute saliva The

combined saliva from all these sources amounts to

a quart (1 liter) of fluid daily

In composition, saliva is 99.5 percent water

Saliva serves important functions: It acts as a

lubri-cant, as a moistening agent and as a dissolving

agent for flavors as food is chewed and swallowed

Saliva contains mucins, slippery PROTEINSthat

pro-vide the lubricating action Without water and

mucins, swallowing would be very difficult Saliva

contains the digestive enzyme AMYLASE, which

ini-tiates starch DIGESTION, and chewing food

thor-oughly to a uniform paste assists starch breakdown

by this enzyme Saliva also contains ions

(elec-trolytes)—SODIUM, CHLORIDE, and BICARBONATE

Chloride activates amylase These minerals are

later absorbed and recycled For defense, saliva

contains lysozyme, an enzyme that ruptures somedisease-producing bacteria, and a protective ANTI-BODY, secretory IgA, that can bind to foreign mate-rials, including viruses, bacteria, and yeast, toreduce this risk of infection

Salivation is controlled exclusively by the NER VOUS SYSTEM Savory aromas, visual images, sounds

-of food preparation, and memories can stimulatesalivation Salivation also occurs in response to irri-tating foods and with nausea Saliva flow after eat-ing flushes chemical remnants out of the mouthand adjusts the acidity to neutral Dehydration candecrease salivation A variety of medications, such

as antihistamines (diphenylpyraline and azatidine),diminish mucous secretions, including saliva.Stress stimulates the sympathetic nervous system

to reduce salivation On the other hand, dryness ofthe mouth promotes thirst sensations (See alsoDEGLUTITION; TASTE.)

salmon (Oncorhynchus) A saltwater fish valued

as a food fish, and as a sport fish The word salmon

is derived from the Latin salmo, which means

“leap-ing.” Salmon can weigh up to 65 lb and measure

up to 3 ft long Varieties include the Atlanticsalmon and the five varieties of Pacific salmon:

sockeye (red) salmon (O nerka), both canned and sold fresh; Chinook (king) salmon (O tschawytscha),

the largest and fattiest variety; coho (sliver) salmon

(O kisutch), smaller fish, sold fresh; pink back) salmon (O gorbuscha), the smallest variety,

(hump-bland flesh, sold canned; and chum (dog) salmon

(O keta), lower in fat and with pale flesh Salmon

are a migratory fish that spawn in fresh water.Young fish live in fresh water for two years beforemigrating to the sea Pollution, dam construction,and overharvesting have drastically reduced thenumbers of this food fish in many parts of theworld Commercial salmon comes from manycountries, such as Chile, Norway, and Canada(eastern Canada and British Columbia) Importedsalmon are generally pen-raised rather than wildfish Domestic, pen-raised salmon are also readilyavailable In the United States, Maine, Alaska, andWashington support most major salmon fisheries,and canned salmon comes from the northernPacific Most Atlantic salmon comes from Canadaand Norway

salmon 567

Salmon is an oily fish, rich in beneficial marine

lipids Salmon fat contains 30 percent to 40 percent

omega-3 polyunsaturated FATTY ACIDS, mainly EPA

(EICOSAPENTAENOIC ACID) and DHA (DOCASAHEXA

-ENOIC ACID) These polyunsaturates are believed to

decrease the risk of STROKE and CARDIOVASCULAR

DISEASE They decrease the risk of blood clots by

inhibiting blood platelet aggregation Platelets are

cell fragments in the blood that initiate clotting

Pen-raised salmon are more likely to be

conta-minated with industrial pollutants when grown in

waters near industrial areas Consumer advocates

have criticized seafood safety in the United States

PCB contamination has been detected in fresh

salmon although the levels were below tolerance

limits set by the U.S FDA Canned salmon sold in

the United States comes from the Pacific off the

coast of Alaska, an area less likely to be polluted by

industrial waste Salmon is smoked, poached,

grilled, marinated, baked, or canned The nutrient

content of 3 oz (85 g) of broiled salmon is: 140

calories; protein, 21 g; fat, 5 g; cholesterol, 60 mg;

thiamin, 0.18 mg; riboflavin, 0.14 mg; niacin, 5.5 g

(See also FISH OIL; OMEGA-3 FATTY ACIDS; SEAFOOD.)

salmonella A bacterium that includes more than

1,300 strains that frequently causes FOOD POISON

-ING Salmonella does not form spores and is

destroyed by heat Its usual habitat is the intestinal

tract of an animal host Salmonella occurs in

ani-mal feed, food processing plants, and food

han-dling, and the bacteria are easily spread by fecal

contamination Flies, rodents, and insects that

con-tact infected fecal material may also contaminate

food Sewage-contaminated water is known to

carry salmonella and cause disease

Livestock and poultry are major sources of

human infection About one in 20,000 eggs is

con-taminated Thoroughly cooking eggs destroys the

bacteria According to the U.S Centers for Disease

Control and Prevention, most cases of salmonella

poisoning are caused by eating undercooked eggs

in sauces, salads, and processed foods Salmonella

grows readily in milk and milk-derived dishes such

as custard, egg dishes, and salad dressing MEATand

meat products like SAUSAGE, meat pies, sandwiches,

and chili can become contaminated when allowed

to stand at room temperature for several hours if

infected by a food handler

salmonellosis A form of food poisoning caused

by salmonella Salmonellosis is one of the threemost common food-borne diseases associated withbacteria, and it is one of the fastest growing food-borne illnesses Every year about 40,000 cases ofsalmonellosis are reported in the United States Theactual number of cases may be much higherbecause many people who have been infected donot seek professional care and are therefore notdiagnosed and reported Illness caused by salmo-nella is more common during the summer months,and children are more likely to be infected Salmo-nellosis can be fatal, especially in young children,the immunocompromised, and elderly people.About 1,000 persons die each year from acute sal-monellosis Some strains of salmonella resist antibi-otics, and dairy cattle fed antibiotics were the likelysource of a drug-resistant salmonella strain thatcaused a large U.S outbreak of food poisoning,involved six states in 1985 This outbreak caused1,000 deaths, 35,000 hospitalizations and left anestimated 125,000 people with increased risk ofchronic illnesses such as ARTHRITIS, osteomyelitis,ankylosing spondylitis, and COLITIS

Salmonellosis often causes flu-like symptoms.Fever, abdominal cramping, headache, DIARRHEA,and vomiting generally appear 12 to 36 hours aftereating tainted food Symptoms may last from twodays to a week Illness is most severe in those withweakened immune systems, commonly found invery young children and in elderly people.Maldigestion and MALABSORPTION can result fromintestinal damage due to this disease

Salmonellosis was almost unknown in theUnited States 40 years ago Increased volume andspeed of food production, increased drug resistance

of bacteria, and relaxed enforcement by ment agencies contributed to widespread contami-nation of food, especially POULTRY Raw milk, rawcheese, any raw or undercooked meat, includingsalami and hamburger, and fresh eggs can be cont-aminated by feces and fecal bacteria and can thus

govern-be a potential source of contamination Pasteurizedeggs are used to prepare commercial MAYONNAISE,and it is not a carrier Freshwater as well as marinefish caught from waters highly polluted by rawsewage may be contaminated by salmonella.All food handlers should thoroughly wash theirhands before handling food to eliminate fecal con-

568 salmonella

tamination They should carefully clean all

equip-ment used in food preparation, including cutting

boards Raw vegetables should not come into

con-tact with utensils used to prepare raw meat and

poultry Food should be refrigerated Salmonella is

destroyed by heating at 140° F (60° C) for 20

min-utes or at 149° F (60° C) for three minmin-utes (See

also BOTULISM.)

Olsen, S J et al “The Changing Epidemiology of

Salmo-nella: Trends in Serotypes Isolated from Humans in

the U.S., 1987–1997,” Journal of Infectious Diseases 183

(2000): 756–761.

salt See SODIUM

salt substitutes (potassium chloride, lite salt,

low-sodium salt) A combination of chemicals that

taste like table salt but contains less SODIUM

Exces-sive salt in the diet can cause HIGH BLOOD PRESSURE

in hypertensive people who are sodium sensitive

Most salt substitutes are mixtures of table salt

(sodium chloride) and POTASSIUM chloride

Potas-sium is an essential nutrient in its own right and

can lower blood pressure in some people Excessive

potassium can irritate the stomach and might start

an ulcer Diseased or damaged kidneys may not be

able to excrete potassium properly; a toxic excess

can accumulate Therefore, patients taking certain

DIURETICS (water pills), beta blockers or

non-steroidal anti-inflammatory drugs; who are

dia-betic; or who have kidney disease are advised to

avoid such salt substitutes The safest strategy is to

cut back on salt entirely and to use herbs and spices

to improve the flavor in place of table salt There

are many different herbs to choose from, each with

its own different, pleasing flavor Consider CAYENNE

pepper, basil, garlic powder, mace, marjoram, SAGE,

savory and thyme, or blends (See also FOOD ADDI

-TIVES; HYPERTENSION.)

salt tablets See SODIUM

SAMe See S-ADENOSYLMETHIONINE

sardine Various small saltwater fish, including

alewife, Atlantic HERRING, pilchard, and sprat The

name probably originated from the small

Mediter-ranean fish in the vicinity of the island of Sardinia.Sardines are a fatty fish Atlantic herring is a goodsource of OMEGA-3 FATTY ACIDS, the essential fattyacids thought to protect against heart attacks.Sardines are rich sources of calcium because thefish is cooked bones and all Its soft bones con-tribute to a high calcium content A 4 oz serving ofsardines provides 50 percent of the REFERENCE DAILY INTAKE(RDI) of calcium and 20 percent of the RDI

or iron Sardines contain significant levels of salt.The same 4 oz serving provides approximately 600

mg of sodium, one-third to one-half of the amountjudged safe

Sardines are often packed in oil, which increasestheir calories Sardines packed in olive oil would bepreferable to those packed in soybean oil because

of olive oil’s greater stability and protective effectsagainst heart disease Norwegian sardines are oftenpacked in sardine oil, which has a high content ofomega-3 fatty acids Blot the fish in oil with a papertowel before eating them, to remove excess oil and

to lower calories Sardines packed in water are nowavailable The nutrient content of 3 oz (85 g) ofsardines (canned, packed in soybean oil, drained,and including bones) is: 175 calories; protein, 20 g;fat, 9.4 g; cholesterol, 85 mg; calcium, 371 mg;iron, 2.6 mg; thiamin, 0.03 mg; riboflavin, 0.17 mg;niacin, 4.6 mg

sarsaparilla (Smilax sarsaparilla) A medicinalherb native to tropical regions of South Americaand the Caribbean This perennial evergreen grows

as a vine; its roots are used in botanical medicine.Europeans learned of its use from Native Ameri-cans According to folk traditions, sarsaparilla hasbeen used as a tonic (to improve body function)and in the treatment of coughs, digestive disorders,fever, gout, skin conditions, and arthritis Exter-nally it has been used for burns and wounds Notoxicity has been reported, though the effects oflong-term, high-level consumption are unknown.Sarsaparilla contains a family of saponins,steroid-like molecules that appear to bind cell wallmaterials released by bacteria in the intestine.Endotoxins can be absorbed by the gut and passinto the bloodstream unless removed by the liver

By rendering endotoxins unabsorbable, sarsaparillamay improve liver function and decrease the bur-den of foreign materials The plant does not contain

sarsaparilla 569

testosterone, the male hormone, and does not

increase muscle mass Thus, there is little evidence

to support the contention that sarsaparilla acts as a

sexual rejuvenator Sarsaparilla extracts have been

routinely used to flavor beverages, candy, baked

goods, and other foods

satiety The sense of being filled up and having

APPETITEsatisfied, as opposed to HUNGER Appetite is

a complex phenomenon involving many

psycho-logical and biochemical factors No single event is

likely to control it Fat and oils in foods slow

emp-tying of the stomach and contribute to the feeling

of being full Researchers are exploring the

hypoth-esis that depleted fat cells may signal the brain to

eat and cause hunger after weight loss LEPTIN, a

recently discovered protein produced by fat cells,

has been shown to enter the brain and control the

consumption of fatty foods Dietary FIBER,

undi-gestible plant material, swells when moistened,

creating a feeling of fullness As a further benefit,

fiber displaces calorie-rich foods, so fewer calories

are eaten

Mechanical contact with food triggers the

stom-ach and intestine to release gut peptides that trigger

satiety This feedback mechanism requires 10 to 20

minutes, while signals are being sent back to the

brain As an example, the hormone CHOLECYS

-TOKININsignals the brain to stop sending hunger

sig-nals after eating Whether cholecystokinin can be

manipulated by dietary changes is not known for

certain Brain peptides are also probably involved in

regulatory food consumption and satiety

Entero-statin decreases fat intake in experimental animals

The development of drugs to increase satiety is

cur-rently an area of active research Strategies to

pro-mote a feeling of satiation and to curb appetite

include eating a snack a half-hour before a meal,

eating slowly and chewing each bite thoroughly

and waiting 20 minutes before taking a second

helping These approaches give the hormone time

to reach the brain and create a feeling of fullness

(See also APPETITE SUPPRESSANTS; CRAVING.)

saturated fat FATthat contains a high percentage

of saturated FATTY ACIDS and exists as a solid at

room temperature Saturation is a chemical

con-cept, referring to the fact that carbon atoms in the

fatty acid molecules are bonded to a maximumnumber of hydrogen atoms (“filled up”) Typicalsources of saturated fat are animal fat, as found inBEEF, veal, LAMB, PORK, meat products, MILK, EGGS,BUTTER, and products like ICE CREAM, milk, andCHOCOLATE Certain plant oils are also saturated,including COCONUT OIL, PALM, and palm kernel oils.Unsaturated fat (vegetable oils) can be converted tosaturated fats by a chemical process called hydro-genation, and these appear on the market as veg-etable shortening

Saturated Fatty Acids

Common building blocks of fats and oils, theseorganic acids contain a maximum number ofhydrogen atoms and lack double bonds Fatty acidsare built of carbon chains, which may be long orshort Long-chain, saturated fatty acids includePALMITIC ACID (16 carbon atoms) and STEARIC ACID(18 carbon atoms) They are waxy solids at roomtemperature and can form fats that are also solids atroom temperature Typical short-chain saturatedfatty acids include: acetic acid (containing two car-bon atoms), propionic acid (with three carbonatoms), and BUTYRIC ACID (four carbon atoms).Medium-chain fatty acids include CAPRYLIC ACID(with eight carbons); capric acid (10 carbons); lau-ric acid (12 carbons); and myristic acid (14 carbons).All saturated fatty acids are readily oxidized bymitochondrial enzyme systems to produce energywith carbon dioxide and water as waste products.Fatty acids yield more than twice the amount ofenergy as carbohydrate and protein when they areburned (See also ESSENTIAL FATTY ACIDS.)

saturated vegetable oils See TROPICAL OILS

sauce A flavorful relish or liquid dressing servedwith foods Sauces are usually high-FAT foods.Stroganoff and orloff usually contain butter Hol-landaise and bearnaise sauces contain butter andegg yolks; bearnaise contains undercooked raw eggyolk and so is a potential source of food poisoning.MAYONNAISEcontains egg yolks, VINEGAR, and a veg-etable oil Brown sauces (bordelaise and bour-guignon) may be lower in fat if fat has beenskimmed off and if butter has not been added Tar-tar sauce and remoulade are flavored mayonnaise

570 satiety

sauerkraut Fermented white CABBAGE Cabbage

is pickled in salt, spices, and cabbage juice by lactic

acid-producing bacteria The lactic acid gives

kraut its characteristic sour flavor Canned

sauer-kraut also has a very high sodium level (up to 780

mg per half-cup) It can be strained and rinsed to

decrease the sodium content Dill seed and onion

can be used to enhance the flavor of sauerkraut

(See also FERMENTATION; FOOD PRESERVATION.)

sausage A seasoned, ground meat product

usu-ally containing high levels of SODIUM and FAT and

packed in a casing The term sausage is derived from

the Latin salsicius, meaning “seasoned with salt.”

Most sausage contains highly seasoned, finely

ground beef and pork and table salt Any meat from

a USDA-inspected carcass can be used to make

sausage and animal fat can be added Thus, blood

sausage is made from blood, pork fat, and

season-ing The final product may be cured (smoked) and

dry or semidry Dry and semidry sausage may

con-tain NITRITES as preservatives, which have been

linked to an increased risk of stomach cancer if

con-sumed in large amounts Fresh sausage is made

from raw meat and must be cooked Semidry

sausage has been smoked; dry sausage may or may

not be smoked; and cooked sausage is ready to eat

Examples include BOLOGNA, braunschweiger,

frank-furter, head cheese, knackwurst, LIVERWURST,

salami, souse, and Vienna sausage

Sausages contain ample protein, iron, and many

B vitamins; however, they also contain almost 55

percent of their calories as fat A few brands

con-tain less than 40 percent of their calories as fat

Tofu and turkey sausage may contain less fat than

pork or beef products It is recommended that

sausage be eaten as a condiment or flavoring with

foods rather than as a main dish

Pork sausage, cooked, can provide 72 percent of

calories as fat; fat accounts for 31 percent of the

weight One link, 13 g, provides 50 calories;

pro-tein, 2.5 g; carbohydrate, 0.1 g; fat, 4 g; cholesterol,

11 mg; sodium, 168 mg; thiamin, 0.1 mg;

ribo-flavin, 0.03 mg; niacin, 0.59 mg (See also CHICKEN;

MEAT, PROCESSED; MEAT SUBSTITUTES; POULTRY.)

sauté Refers to pan frying small strips or slices of

food quickly in a hot skillet with a small amount of

butter or oil Be sure oil is hot before adding foods

to minimize the amounts of oil they soak up Porkslices, veal scallops, chicken breast, fish fillet, tofu,onions, carrots, garlic, and other vegetables andgrains can be sauteed

saw palmetto (Serenoa repens) A small palmtree native to South Carolina, Georgia, and Floridathat produces berries with medicinal properties.Saw palmetto berries have a long history of use byNative Americans, while later European physiciansused the berries to treat enlarged prostate (benignprostatic hyperplasia), genitourinary tract imbal-ances, and as a tonic to boost nutrient and generalbody functioning Modern formulations employ afat-soluble extract of saw palmetto berries contain-ing large-molecular-weight alcohols and plantsterols, compounds related to cholesterol Saw pal-metto berry extracts block the conversion of themale sex hormone, testosterone, to a more potentcompound, dehydrotesterone, that promotes pro-static enlargement, and promote the breakdown ofthe more active compound These effects may pos-sibly explain the saw palmetto relief of commonsymptoms such as decreased urination at night,increased urinary flow rates, and decreased resid-ual urine content in the bladder No significant sideeffects of saw palmetto berry extracts or berrieshave been noted

School Breakfast Program A federal program toprovide funds for nutritious breakfasts for chil-dren The National School Breakfast Program wasestablished by the Child Nutrition Act of 1966 anauthorized as a permanent appropriation in 1975.Fewer children participate in the BREAKFAST pro-gram than in the SCHOOL LUNCH PROGRAM In the1999–2000 school year 7.6 million children partic-ipated in the breakfast program, while 27.4 millionchildren participated in the lunch program Usu-ally a state’s Department of Education administersthis program

The school breakfast must contain one serving

of meat or meat alternative (such as eggs or peanutbutter), two or more servings of different fruits orvegetables, and one serving of milk

Factors weighed in planning school food serviceprograms include: cultural and ethnic backgrounds

School Breakfast Program 571

of students, needs of handicapped students, as well

as fitting meals to accommodate class and bus

schedules Practical nutrition education can be part

of breakfast programs Evaluation of school

nutri-tion programs finds that most students

participat-ing in school breakfast programs are from

low-income families

Breakfast is considered the most important meal

for both children and adults because of its positive

impact on performance and alertness Nonetheless,

many Americans skip breakfast, especially

teen-agers Students who skip breakfast have higher

rates of tardiness, higher absenteeism and lower

performance, and more FATIGUE Researchers

shows that low-income children who participate in

the School Breakfast Program have higher

stan-dardized achievement test scores than children not

in the program (See also HUNGER; WIC.)

School Lunch Program A federal program

estab-lished under the National School Lunch Program of

1946 to protect the health of U.S children through

the consumption of nutritious foods The act

authorized state grant-in-aid program to provide

cash and food The cost is shared among the USDA,

state and local governments, and children’s

fami-lies Household income determines whether a child

will receive a reduced rate or free meal To qualify,

household income must be below 185 percent of

the federal poverty level; for free meals household

income must fall below 130 percent of the poverty

level

The National School Lunch Program is open to

public and private schools and to residential child

care institutions Schools that participate in the

program receive financial assistance, donated

sur-plus commodities and technical assistance in

equipping and managing the program In the

1970s, the Nutrition Education and Training

Pro-gram was developed to educate students about the

relationship between nutrition and health, to train

food service personnel in management, and to

instruct teachers in nutrition education The

pro-gram was expanded due to increased need for

low-cost, subsidized meals, especially among

eco-nomically disadvantaged children

On a typical day in school year 2000–2001, 15.6

million children participated in the program The

program has continued to serve nutritious schoollunches to children who would not likely receivelunch from another source Furthermore, schoollunches have provided approximately 33 percent ofthe RECOMMENDED DIETARY ALLOWANCES(RDAs) forchildren of various ages Eligibility for participation

in the program is contingent upon operating on

a nonprofit basis, providing free or reduced price lunches to needy children, making lunchesavailable to all children providing dining andkitchen facilities, avoiding segregation of needychildren and serving meals that conform to USDAguidelines

School lunches must meet the DIETARY GUIDE LINES FOR AMERICANS, which recommend that nomore than 30 percent of a person’s calories comefrom fat and less than 10 percent from saturatedfat The lunches should also provide one-third ofthe U.S RDA of protein, iron, calcium, and vita-mins A and C In 2001 the Physician’s Committeefor Responsible Medicine issued a report that foundthat many school lunches offered in the NationalSchool Lunch Program did not meet these require-ments Only one in 12 elementary school districtssubstituted lower-fat, cholesterol-free plant protein

-in place of meat, and one-fourth were not meet-ingUSDA nutrition requirements

scromboid fish poisoning A type of FOOD POISON INGthat occurs within an hour after eating species

-of spoiled fish that populate tropical oceans, ing TUNA, MACKEREL, skipjack, BONITO, HERRING,mahi-mahi, SARDINES, and anchovies An impor-tant clue to contamination is that infected fish tastemetallic and peppery Symptoms of poisoning in-clude flushing, sweating, nausea, vomiting, diar-rhea, headache, and dizziness Antihistaminesrelieve the symptoms Scromboid fish poisoningcan be prevented by keeping fresh fish on ice

includ-or refrigerated until it is cooked (See also FOOD TOXINS.)

scurvy A disease caused by severe deficiency ofVITAMIN C (ascorbic acid) Scurvy has been de-scribed since ancient times Long sea voyages of the15th through the 17th centuries frequently deci-mated the ranks of sailors As early as 1593, aBritish admiral demonstrated that lemon juice

572 School Lunch Program

cured the disease A Scottish naval surgeon

con-ducted the first controlled experiment in the

treat-ment of scurvy in 1753, which proved that citrus

fruits protected seamen and cured scurvy Not

until 40 years later were limes routinely issued to

British seamen to prevent scurvy However, scurvy

continued into more recent times It was prevalent

during the American Civil War, and in 1912 half

the men on Scott’s expedition to the South Pole

died of scurvy

During initial stages of vitamin C deficiency, an

individual may feel listless Wounds may heal

slowly and gums may bleed easily Bruising occurs

easily Minute hemorrhages appear around hair

follicles or stomach, buttocks, legs, and arms Later

stages are characterized by weight loss, weakness,

painful muscles, swollen joints, spongy gums, and

loss of teeth Vitamin C plays several important

roles that can be related to scurvy Chief among

these is the requirement for vitamin C in COLLAGEN

The formation of mature collagen, the major

struc-tural protein of connective tissue, relies on the

availability of key building blocks called

hydrox-yproline and hydroxylysine The production of

hydroxyproline from proline and of hydroxyl

lysine from lysine requires vitamin C As a versatile

antioxidant and key support nutrient of the

immune system, vitamin C exhibits wide-ranging

benefits on health Modest deficiencies do not

manifest themselves as scurvy, rather they increase

the susceptibility to infections and oxidative

dam-age leading to chronic diseases

Infants relying on cow’s milk may be prone to

scurvy because much of the vitamin C is destroyed

during pasteurization Infants require

proportion-ately higher levels of vitamin C because of their

high rate of tissue growth Breast milk contains

adequate vitamin C to support infant

develop-ment

Among adults, low-income elderly persons are

susceptible to scurvy if they do not eat fresh fruit

and vegetables Overcooking destroys most vitamin

C in vegetables Chronic disease, injuries, and

surgery are more likely in this group, and these

conditions deplete the body stores of this vitamin

(See also MALNUTRITION.)

Rajakumar, Kumaravel “Infantile Scurvy: A Historical

Perspective,” Pediatrics 108, no 4 (2001): e76.

seafood Edible marine fish and shellfish such asCLAMS, mussels, scallops, OYSTERS, LOBSTERS, andSHRIMP that represent an important, highly nutri-tious food source It is low in saturated fat and calo-ries and is a good source of PROTEIN, IRON, VITAMIN

B12, IODINE, PHOSPHORUS, ZINC, and COPPER Fish andfish oil are particularly rich in the omega-3 family

of polyunsaturated FATTY ACIDS, which help reduceINFLAMMATIONin conditions like ARTHRITISand pso-riasis, as well as reducing the risk of blood clot for-mation, thus offering protection against HEART ATTACKS COD LIVER OILcontains high levels of VITA-MIN A and VITAMIN D, which may be toxic whenconsumed in large amounts Several servings perweek of the following fatty fish are recommended:bluefish, butterfish, halibut, herring, mackerel,striped bass, orange roughy, smelt, salmon, sar-dines, trout, and pompano

The larva of parasitic worms may contaminateraw fish, including Pacific salmon, Pacific red snap-per (rockfish), and herring; thus raw fish dishes(sushi, sashimi, CEVICHE, lomi-lomi) carry a risk ofparasitic disease, such as anisakiasis Inadequatelysmoked or salted fish can carry parasites Thesevere abdominal pain of such a disease is due toacute intestinal inflammation The parasite is killed

by cooking marine fish thoroughly Pregnant andnursing women, very young children, and elderlypeople should avoid raw fish and shellfish to mini-mize this risk

Chemical Contamination

Chemical contaminants are another prominentissue in seafood safety Fish and shellfish are gen-erally more susceptible to chemical contaminationthan meat and poultry because they filter hugeamounts of water through their bodies and feed onother organisms in which contaminants may beconcentrated Clams and oysters can filter 15 to 20gallons of water daily While thorough cookingdestroys parasites and microorganisms, this doesnot eliminate chemical pollutants like LEAD, chlor-dane, DIOXIN, DDT, MERCURY, PBBs, and PCBs Suchindustrial chemicals were once widely used in PES-TICIDES, electrical insulation, plastics, dyes, andother products Over decades these environmentalpollutants have crept into the FOOD CHAINbecausethey are not readily broken down and because theytend to accumulate in plants and animals

seafood 573

Varying levels of pollutants have been reported

in both domestic and imported fish While levels of

detected pollutants have generally fallen below

FDA tolerance limits, those limits were set when

fish consumption was lower and consequently

people accumulated less of these pollutants The

level of pollutant can vary with the source, but in

many markets it is often difficult for the consumer

to determine the source of fish sold Pollutant

lev-els in salmon from Pacific waters may be lower

than from other sources; however, the fish the

con-sumer buys may come from Chile, Norway, Eastern

Canada, Maine, as well as from Washington,

Alaska, or British Columbia

Chemical pollutants may increase the risk of

certain cancers, birth defects, and neurological

damage in unborn children However, the potential

health hazards of long-term, very low-level

expo-sure remain unknown Because residue buildup

occurs over years, it may be hard to trace a disease

cause to a specific pollutant exposure

Shellfish can accumulate disease-causing

bacte-ria and viruses when exposed to untreated sewage

Harvesting is limited to waters that are certified as

being clean, although enforcing the policy is limited

by resources Eating raw shellfish carries the risk of

gastrointestinal disease with symptoms such as

diar-rhea, cramps, nausea, and vomiting Shellfish also

transmit hepatitis A virus Well-cooked shellfish are

safer than raw or semi-cooked shellfish

To ensure that seafood is as safe to eat as

possi-ble, consumers should

• Buy fresh seafood Fish and shellfish spoil easily

and should be handled with care Fresh fish

should have a mild “ocean” smell; they should

not smell “fishy” or smell like ammonia

• Fresh seafood should be bought from reputable

merchants who can identify their source

• Seafood should be refrigerated at home

immedi-ately after purchase to prevent bacterial growth,

minimize spoilage, and reduce the risk of FOOD

POISONING Raw seafood that will not be eaten

within two days should be frozen Most shrimp

have been frozen and thawed, and should be

cooked as soon as possible

• Frozen seafood should be thawed in the

refrig-erator or in cold running water and not

refrozen Other raw shellfish, including lobster,should be alive when purchased

• Cooked shellfish should be refrigerated and used

on the same day

• Mussels, clams, and oysters should be moistenedand refrigerated to keep them alive rather thanstored in plastic bags They should not be storedfor a long time in fresh water

• Any shellfish that remains closed after steamingshould be discarded Raw shellfish that remainclosed are dead and may have begun to decom-pose

• Consumers should follow the same rules in dling raw seafood as when handling raw poultryand raw meat to avoid contaminating cookeddishes or fresh vegetables with bacteria: Washwith soap and water all utensils, countertops,cutting boards and hands that have come intocontact with raw seafood

han-• Consumers should eat a variety of seafoodsrather than a single source to minimize overex-posure to pollutants Elderly people, young children, pregnant women, patients with com-promised immune systems or with liver diseaseshould avoid eating raw seafood

Connor, W E “Importance of n-3 Fatty Acids in Health

and Disease,” American Journal of Clinical Nutrition 71

(2000): 171S–175S.

seafood inspection Fish and shellfish are amongthe most perishable foods, yet seafood is one of theleast regulated foods; it remains the only flesh thatdoes not undergo mandatory inspection In con-trast, meat and poultry processing facilities areinspected daily A single-time FDA inspection ofmost U.S seafood processing plants revealed a rel-atively low violation rate of up to 5.1 percent ofplants, depending on the region

An estimated 20 percent of food-borne illness iscaused by seafood Seafood can be contaminated

by bacteria, viruses, parasites, and industrial wastesand pollutants While the National Academy of Sci-ences has concluded that most seafood is safe toeat, this advisory organization has also recom-mended increased inspection and regulation of theindustry Fish testing in specific areas is left to stateagencies, and testing for chemical contaminants

574 seafood inspection

remains scattered Only very small numbers or

samples of fish are monitored for chemical

conta-minants The FDA established a new Office of

Seafood in 1991 to address this issue In 1994, the

FDA launched a seafood safety initiative designed

to keep contaminated seafood off the market

shelves Seafood processors need to maintain

detailed records of safety procedures; to identify

where shellfish were harvested; to catch fish only

from waters the government has certified as being

clean; and to store their catch at proper

tempera-tures Ready to eat seafood will have to be cooked

and stored at safe temperatures as well

sea salt A less pure form of table salt (SODIUM

chloride) Sea salt contains low levels of certain

minerals found in sea water Using 3.5 g of sea salt

would supply 22 percent of the REFERENCE DAILY

INTAKE(RDI) of MAGNESIUM; 2.2 percent of the RDI

of IODINE; 2.7 percent of the RDI of CALCIUM

Mag-nesium carbonate is the additive used to prevent

caking This is more healthful than aluminum

sili-cate used for the same purpose in refined salt Sea

salt is not iodized and lacks iodine As a source of

sodium, sea salt carries with it the same risks for

high blood pressure (HYPERTENSION) as ordinary

table salt in susceptible people (See also TRACE

MINERALS.)

seaweed A large family of marine ALGAE Edible

seaweed is one of the richest sources of vitamins

and minerals Sea vegetables provide IODINE, SELE

-NIUM, IRON, CALCIUM, PHOSPHORUS, and MAGNESIUM,

as well as BETA-CAROTENE, VITAMIN E, and the B

COMPLEX Sea vegetables are not an adequate

source of vitamin B12 because they possess

sub-stances that are inactive analogs or forms of the

compound that the body cannot use Vegetarians

who do not eat milk, eggs, fish, or meat should

consider taking a vitamin B12 supplement rather

than relying on seaweed

Traditionally, Asian diets include a variety of

seaweed The edible algae can be categorized as

brown algae and red algae Brown algae are

repre-sented by arame, hijiki, kelp, kombu, and wakame

Arame is a Japanese product; it is softened by

pro-longed cooking, sun-dried, and finally sliced into

strands and packaged Arame contains B complex

vitamins and minerals The calcium content is1,170 mg per 100 g Hijiki is found in the Far East;

100 g (dry weight) contains calcium, 1,400 mg;iron, 29 mg; plus BETA-CAROTENE and B complexvitamins This seaweed is dried, steamed to stiffen

it, again dried, then soaked in arame juice anddried for market Kelp refers to a large family, andmembers are used commercially as a source of foodadditives, EMULSIFIERS, thickeners, and STABILIZERS.Kelp is dried and sold whole, or powdered when it

is used as a flavoring Kelp can be steamed, pickled,

or boiled It contains significant calcium and otherminerals; 100 g contains calcium, 1,093 mg;sodium, 3,007 mg; and potassium, 5,273 mg.Kombu is a general name for several species ofbrown algae Dashi consists of broad strips and isused in soups, while tororo is shaved into sliversthat can be marinated Kombu is often used withroot vegetables, rice, and vegetables It provides sig-nificant beta-carotene, 430 retinol equivalents per

100 mg, as well as the B complex and vitamin C.Wakame comes from Japan It is dried andprocessed for preservation It can be added to soups,like miso soup, cooked as a vegetable, used as a gar-nish, or soaked and then added to salads Wakamecontains calcium, iron, and vitamins; 100 g providescalcium, 1,300 mg; iron, 13 mg; niacin, 10 mg; andvitamin C, 15 mg Brown sea vegetables like kombucontain alginic acid and other ingredients that bindtoxic heavy metals like strontium, cadmium, andradium Alginic acid is used to treat cadmium poi-soning and help remove it from the body

Red algae include carragheen and nori ragheen yields a gum called CARRAGEENAN that isused in prepared foods, primarily for its ability toform gels in puddings, jellies, and the like Car-rageenan inhibits herpes simplex virus (oral andgenital forms) as well as tumor-inducing RNAviruses in test tube experiments It also provides(per 100 g): calcium, 885 mg; sodium, 2,892 mg;and potassium, 2,844 mg Nori is a cultivated redsea vegetable Fresh nori is washed, chopped intofragments, dried, and packaged Sheets of nori arewrapped around rice used in sushi and Californiarolls Nori provides (per 100 g): calcium, 260 mg;iron, 12 mg; high levels of beta-carotene, 11,000retinol equivalents; thiamin, 25 mg; niacin, 10 mg;and vitamin C, 20 mg

Car-seaweed 575

Seaweed has an ancient history of use in Eastern

medicine, including Chinese and Indian medicine

(Ayurvedic medicine) It has been used to treat

intestinal parasites GOITER, enlarged thyroid due to

iodine deficiency, is effectively treated by seaweed

because of its high iodine content Certain species

of seaweed have been used in folk medicine to

treat high blood pressure, constipation, wounds

and ulcers, GOUT, liver and kidney ailments,

men-strual irregularities, and to improve digestion

Alginic acid is used in some antacids to treat ACID

INDIGESTION and to treat wounds Fucoidin is

another type of complex carbohydrate

(polysac-charide) from seaweed In animals, this material

inhibits chemically-induced cancers (See also FOOD

ADDITIVES; MACROBIOTIC DIET.)

Wein, Bibi “The World’s Healthiest Diet,” Lifestyles 17,

no 3 (March 1995): 172–175.

secretin A HORMONEreleased by the small

intes-tine that blocks the release of gastric juice and

STOMACH ACID Secretin slows the movement (PERI

-STALSIS) of material down the gastrointestinal tract

It stimulates the secretion of BICARBONATE by

pan-creatic duct cells to neutralize the acidic, partially

digested food discharged by the STOMACH into the

small intestine To further prepare the intestine for

DIGESTION, secretin stimulates bile production to aid

fat digestion and the secretion of intestinal juice

and digestive enzymes Secretin release is triggered

by food entering the small intestine, including

par-tially digested carbohydrate and fat, as well as by

fluids that contain high or very low concentrations

of ions (See also ENDOCRINE SYSTEM.)

selenium A TRACE MINERAL nutrient with

anti-cancer and antiaging properties Selenium helps

protect cells against oxidative stress As a part of

the enzyme GLUTATHIONE PEROXIDASE, selenium

serves as an ANTIOXIDANTby destroying highly

reac-tive chemicals that can form FREE RADICALS

Glu-tathione peroxidase destroys HYDROGEN PEROXIDE, a

naturally occurring chemical that is a powerful

oxi-dizing agent Hydrogen peroxide is produced for

antimicrobial defense by macrophages, a type of

white blood cell that engulfs foreign invaders, and

it is a by-product of another antioxidant system

(SUPEROXIDE DISMUTASE) that destroys a highly

reac-tive form of oxygen called superoxide Glutathioneperoxidase neutralizes oxidative damage to lipids incell membranes, thus limiting their damage due tofree radical attack Selenium may possess otherantioxidant properties as well

Selenium is generally recognized as an cancer agent In selenium-deficient experimentalanimals, LIVER cells become defective and moreprone to become cancerous when activated Stud-ies show that populations with a low seleniumintake are more prone to gastrointestinal, breastand rectal cancer Deficiency of selenium leads tolowered glutathione peroxidase activity Further-more, extensive Chinese studies have suggestedthat selenium supplementation provides protec-tion against hepatitis B and liver cancer Seleniummay inhibit the development of cancer by blockingthe activation of certain cancer-promoting genes,

anti-by inhibiting viruses linked to cancer or anti-by porting healthy cell division and protecting cellsagainst oxidative damage that could damage theirDNA

sup-Selenium supports a healthy IMMUNE SYSTEM,where it stimulates antibody production and defen-sive cells (lymphocytes, macrophages and naturalkiller cells) Some AIDS patients may be seleniumdeficient Selenium can block mercury, arsenic,and cadmium poisoning Damaged heart muscle(cardiomyopathy) has occurred in patients fedintravenously mixtures that lacked selenium, andpopulations in areas of China characterized byregional selenium deficiency are more diseaseprone OSTEOARTHRITISin Chinese children has alsobeen linked to selenium deficiency

RECOMMENDED DIETARY ALLOWANCES(RDA) lished in 1989 proposed a selenium RDA for thefirst time as 70 mcg/day for men and 55 mcg fornonpregnant, nonlactating women Obtaining ade-quate selenium is a growing problem in the UnitedStates Regions like the Pacific Northwest, theGreat Lakes region, and some southern states(Georgia and the Carolinas) possess low soil con-centrations of selenium, and vegetables and grainsgrowing in depleted soils contain only low levels ofselenium Possibly, acid rain prevents plants fromtaking up this mineral from soil The average U.S.intake is about 100 mg/day

pub-Good dietary sources of selenium include organmeats, such as liver and kidney; BREWER’S YEAST;

576 secretin

ocean FISHand SHELLFISH; and red MEAT Vegetable

sources (if grown in soil with enough selenium) are

ONIONS, GARLIC, MUSHROOMS, and BROCCOLI

Aspa-ragus, cabbage, and whole grains contain small

amounts of selenium FRUITSand most VEGETABLES

and drinking water generally provide little

sele-nium Supplements containing inorganic selenium

(sodium selenite or sodium selenate) should

prob-ably be taken separately from large amounts of

vit-amin C to avoid interference

Chemically combined selenium represents the

most prevalent form of the selenium in the typical

diet Selenium can replace sulfur in the amino

acids CYSTEINEand METHIONINEto form the analogs,

selenocysteine and selenomethionine

Selenocys-teine occurs in a variety of proteins including

glu-tathione peroxidase and is found in meat

Selenomethionine cannot be synthesized by the

body and is supplied in the diet by a variety of

foods It can substitute for methionine in a variety

of the body’s proteins The breakdown of

methion-ine and selenomethionmethion-ine releases cystemethion-ine and

selenocysteine, respectively

Safety

Toxicity can occur with daily consumption of 5 mg

Toxic levels of selenium occur in agricultural

drain-water in some states Certain regions are

character-ized by high levels of selenium (North and South

Dakota and the San Joaquin Valley of California)

Soils with high selenium cause unusually high

lev-els in plants such as wheat Symptoms of selenium

toxicity include skin sores, garlic breath, fingernails

with ridges and bumps, hair loss, and lethargy

Severe toxicity is indicated by fragile, black nails,

metallic taste, dizziness, peripheral nerve damage,

nausea, weight loss, and jaundice Children, elderly

persons and people with chronic illnesses may

tol-erate less selenium in their diets, while physically

active people may tolerate more Sodium selenite,

the inorganic form of selenium, can cause cancer at

very high doses Organic selenium that occurs in

foods is not carcinogenic

Cammack, P M “Selenium Deficiency Alters Thyroid

Hormone Metabolism in Guinea Pigs,” Journal of

Nutrition 125 (1995): 302–308.

self-rising flour See BAKING SODA

semolina Milled durum WHEAT used to producePASTAlike macaroni and spaghetti The high protein(gluten) content of durum wheat lends itself toelastic, resilient dough that is suitable for themechanical processing involved in making pasta

senility An old-fashioned term for memory lossassociated with AGING This phenomenon usuallybegins with loss of short-term memory and theability to process new information quickly Recol-lection of past events also slows down ALZHEIMER’S DISEASEis the most common of the more than 70types of dementia It currently affects 4 millionAmericans but experts believe that will rise to 22million by 2025

Many of the people who appear to be sufferingfrom dementia and forgetfulness may instead havenutritional deficiencies, including VITAMIN B12defi-ciency due to inadequate absorption The uptake ofthis vitamin declines with age, especially in thosewith stomach troubles Injections of vitamin B12,

or taking large doses in tablet form, is a preventivemeasure

Forgetfulness, learning difficulties, and lems remembering new things can frequently becaused by overmedication Many elderly U.S citi-zens (65 or older) take prescription drugs theyshould not be using, some of which may cause con-fusion or amnesia Similar problems may be due toadverse reactions to medication As an example,DIURETICS(water pills) can cause excessive sodiumloss, especially for those on a salt-restricted diet.This condition, called hyponatremia, is easilydetected if the change is dramatic However, if thechange is slow, it is more difficult to detect and thesymptoms match senile dementia This condition isreversible if caught soon enough Memory loss isalso worsened by drugs blocking the formation ofneurotransmitters Drugs that fall into this categoryinclude sleeping pills and medications for reducingtremors, decreasing stomach acid and calmingnerves Other possible causes of forgetfulnessinclude high fever, minor head injuries, DEPRES-SION, loneliness, and boredom To combat senility,exercise the brain by keeping mentally active andavoiding drugs that characteristically cause a drymouth because this class of drugs may interferewith neurotransmitters

prob-senility 577

Prescription drugs Hydergine, the hormone

vasopressin (antidiuretic hormone), and

unipoce-tine have been used to enhance memory Lipids

like phosphatidylserine and

phosphatidylethano-lamine play structural roles in cell membranes, and

treatment with these substances suggests some

improvement in certain patients with Alzheimer’s

disease CHOLINE and LECITHIN (the phospholipid

derivative of choline) may improve short-term

memory in susceptible patients However, they do

not appear to alter the course of Alzheimer’s

dis-ease Treatment with phosphatidylcholine and

pre-scription drugs like physostigmine and Hydergine

have yielded mixed results Three decades of

research suggest that phosphatidyl serine benefits

cognitive function, including memory and learning

in elderly people Other studies indicate that a

derivative of the amino acid CARNITINE,

L-acetylcar-nitine, shows promise in moderating age-related

depression, as well as the effects of stroke and

nerve degeneration related to DIABETES MELLITUS

(See also FOOD; GINKGO; PREBIOTICS.)

Le Bars, P L “A Placebo-Controlled Double-Blind,

Ran-domized Trial with a Special Extract of Ginkgo Biloba

in Dementia,” JAMA 278 (1997): 1,327–1,332.

sensitivity See FOOD SENSITIVITY

sequestrants (chelating agents) Agents used to

reduce color changes and SPOILAGE in canned

foods, PROCESSED FOODS, and bottled salad

dress-ings Sequestrants bind metal ions like iron, which

catalyze the reaction of oxygen with sensitive

materials in food Examples of sequestering agents

are CITRIC ACID, malic acid, tartaric acid, and EDTA

Citric acid is used in ice cream, sherbet, fruit drinks,

soft drinks, jellies, canned fruits and vegetables,

and cheese It is considered a safe additive EDTA is

widely used in salad dressings, MARGARINE, MAYON

-NAISE and sandwich spreads, prepared fresh fruit,

potatoes, canned shellfish, beer, and soft drinks

EDTA too is considered safe (See also FOOD ADDI

-TIVES; MINERALS.)

serine (Ser, L-serine) A nonessential AMINO ACID

required to synthesize proteins Serine plays a role

in many synthetic reactions that require FOLIC ACID,

VITAMIN B6, and NIACIN It can be converted to thesimplest amino acid, GLYCINE, and vice versa Serinecan assist in the synthesis of PURINES and PYRIM-IDINES, the building blocks of DNA and RNA Serinecan be converted to ethanolamine and CHOLINE,two nitrogen-containing compounds required forphospholipid synthesis and cell membrane forma-tion, and to certain NEUROTRANSMITTERS, brainchemicals required to transmit signals in nerves.Serine is classified as a “glycogenic” amino acid be-cause during STARVATION it can be converted toBLOOD SUGARto fuel the brain (See also AMINO ACID METABOLISM.)

serotonin A chemical found in the brain anddefensive cells of connective tissue Mast cells, atype of defensive cell lodged in connective tissue,produce serotonin from the essential amino acidTRYPTOPHAN to slow blood flow in damaged areasbecause it acts as a powerful vasoconstrictor In thebrain, serotonin functions as a neurotransmitter, achemical required for the transmission of nerveimpulses Serotonin is involved in inducing sleep,sensory perception, and temperature It diminishespain, reduces APPETITE, and has a calming effect.Certain antidepressants such as Prozac boost sero-tonin levels Diet can possibly affect mood by alter-ing brain serotonin levels Eating carbohydratesmay reduce the level of most amino acids in theblood except tryptophan, so that this amino acidcan more easily penetrate the BLOOD-BRAIN BARRIERwithout competing with other amino acids.According to this hypothesis, as the level of trypto-phan rises in the brain, more serotonin is synthe-sized, leading to relaxation and decreased alertness.(See also NERVOUS SYSTEM.)

serum The clear, straw-colored fluid remainingafter blood has clotted Serum contains CHOLES-TEROL(serum cholesterol) in the form of LOW-DEN-SITY LIPOPROTEIN(LDL, the less desirable form) andHIGH-DENSITY LIPOPROTEIN(HDL, the more desirableform); fat (TRIGLYCERIDES); proteins produced bythe liver such as serum ALBUMIN; ELECTROLYTES(ionic minerals like SODIUM, POTASSIUM and CHLO-RIDE); waste materials like UREAand URIC ACID; andnutrients such as AMINO ACIDS and BLOOD SUGAR(GLUCOSE) Serum is often used in the clinical labo-

578 sensitivity

ratory to measure these parameters for diagnosis,

rather than whole blood, which contains cells that

can alter these parameters For example, red blood

cells possess their own complement of enzymes,

lipids, and minerals

serum lipids See CHOLESTEROL

sesame (Sesamum indicum) An annual tropical

plant grown since ancient times for its edible seed

oil Sesame was cultivated in Palestine and Syria as

early as 3000 B.C It is now cultivated in China,

India, Burma, and Mexico; the United States is a

major importer Sesame seeds contain 50 percent

oil by weight; the oil can be extracted from

crushed, whole seeds The seed is dehulled for

human consumption because its hull contains 2

percent to 3 percent OXALIC ACID, which binds

min-erals and gives it a bitter flavor The U.S imports 70

million pounds of sesame seeds annually; most of

this is used for hamburger buns Ground sesame

seeds are used in hummus and tahini (a sesame

seed paste) Halvah is a confection made with

ground sesame seeds Sesame seeds are used with

stir-fried vegetables and fried poultry in Asian

cui-sine

Sesame oil is more saturated than VEGETABLE

OILSlike safflower, corn, or soybean oil, which all

contain more than 50 percent polyunsaturated

fatty acids Sesame oil contains 43.8 percent

polyunsaturated fatty acid (LINOLEIC ACID); 14.6

percent saturated fatty acids (mainly PALMITIC ACID

and STEARIC ACID); and 41.5 percent

monounsatu-rated fatty acids (OLEIC ACID) The oil has a strong

nutty flavor and is often used in stir-fry meals The

nutrient content of sesame seeds (15 g) is: 84

calo-ries, protein, 3.6 g; carbohydrate, 0.6 g; fat, 7.1 g;

calcium, 18 mg; iron, 1.1 mg; thiamin, 0.29 mg;

riboflavin, 0.03 mg; niacin, 0.8 mg (See also

HYDROGENATED VEGETABLE OIL.)

set point See DIETING; WEIGHT MANAGEMENT

shellfish Mollusks and crustaceans that have

been long used as food sources Univalve mollusks

such as abalone are enclosed in a single shell;

bivalve mollusks with a two-part shell include

CLAMSmussels, OYSTERS, and scallops Cephalopods(creatures with tentacles, like squid) are a type ofmollusk Crustaceans, which possess a tough outerlayer and segmented bodies and legs, include CRAB,LOBSTERS, crayfish, prawns, and SHRIMP Shellfishprovide rich sources of protein low in saturated fatand total fat, and TRACE MINERALSsuch as IODINE,ZINC, and COPPER Generally, shellfish contain theusual amounts of cholesterol as found in meat.Shrimp contain somewhat higher levels, thoughless than found in eggs Like ocean fish, shellfishcontain omega-3 oils that offer protection againstheart disease

Raw shellfish are a major source of severe, borne disease Disease organisms carried by shell-fish include salmonella and hepatitis A virus.Bacteria can cause gastroenteritis (inflamed stom-ach and intestines) with diarrhea, nausea, vomit-ing, and cramps Shellfish are bottom feeders andfilter vast amounts of water, therefore they tend toaccumulate waste products and disease-producingbacteria and viruses when grown in waters conta-minated by sewage Clams and oysters can filter 15

food-to 20 gallons of sea water daily

FDAand state inspections are designed to makecertain that shellfish are harvested from cleanwaters However, regulation of the shellfish indus-try is spotty because few agents are available tomonitor 10 million acres of approved shellfish beds

in U.S coastal waters To meet the increased sumer demand, the fishing industry is taking fishand shellfish closer to shore, where pollution ishigher and the risk of polluted SEAFOODis higher.Raw or undercooked shellfish are the major

con-seafood hazards The bacterium Vibrio vulnificus

produces a toxin causing a shellfish poisoning ciated with contaminated seafood, especially oys-ters from the Gulf Coast Immune compromisedpeople and those with liver disease (cirrhosis) aremost vulnerable The toxin can cause skin ulcersand occurs as normal marine flora in warmer tem-perate waters Its production is not associated withpollution

asso-RED TIDEis an explosive growth of a microscopicmarine algae Poisonous dinoflagellates produceneurotoxins that are not destroyed by cooking

Paralytic shellfish poisoning is caused by Gonyaulax catenella and G acetenella along Pacific coasts and G tamarensis in the Bay of Fundy and in the St.

shellfish 579

Lawrence estuary on the North Atlantic

Symp-toms begin with numbness in lips and tongue,

spreading to arms and legs and respiratory distress

Red tide can cause blood poisoning and death in

high-risk individuals—patients with liver disease,

AIDS, or alcoholics Mussels gradually destroy or

eliminate bound poisons after an algal bloom In

general, raw oysters should be avoided during the

warmer months, April to October

Razor clams from U.S Pacific Northwest beaches

can be contaminated with domoic acid, a naturally

occurring neurotoxin that causes nausea, fever,

abdominal cramps, short-term memory loss, coma,

and death in severe cases This toxin is produced by

marine plankton Internal organs of Dungeness

crab harvested off the coasts of California, Oregon,

and Washington may be contaminated, although

the crab meat itself is safe (See also SEAFOOD

INSPECTION.)

sherbet A frozen DESSERT prepared from fruit

juice or fruit puree, sugar, milk, egg white, or

gelatin or dipped marshmallows In contrast,

sor-bets are fruit-based frozen desserts that do not

con-tain dairy products (See also ICE CREAM.)

shigellosis A severe type of FOOD POISONINGcaused

by shigella, an intestinal bacterium Symptoms

include very severe DIARRHEA, lasting several days,

with possible bloody stools and accompanied by

fever and possibly DEHYDRATION Most people

recover fairly rapidly, even without treatment with

antibiotics However, shigellosis can be

life-threaten-ing to children and to the elderly Shigella is carried

by fecal matter, and the disease can be transmitted

by food handlers with poor hygiene State law

requires that cases of shigellosis be reported to

health departments (See also SALMONELLA.)

shiitake mushroom (Lentinus edodes; forest

mush-room) An edible MUSHROOMespecially popular in

Asia Shiitake mushrooms are cultivated

commer-cially and are available in United States markets

Shiitake contains a broad spectrum of amino acids,

potassium, and ergosterol, a substance that can be

converted to vitamin D in the presence of sunlight

In addition, shiitake mushrooms have been used in

Asian medicine for thousands of years Shiitake

contains carbohydrate materials and rides, including lentinan, which stimulates theimmune system and which has antitumor activity.Lentinan may boost white blood cells called Thelper cells that gear up the immune system Shi-itake extracts also boost antiviral defenses byincreasing interferon production Extracts canlower blood cholesterol levels

polysaccha-shock See ANAPHYLAXIS

short-chain fatty acids Very small fatty acids thathave an odor (volatile fatty acids) Short-chainfatty acids are produced by the anaerobic fermen-tation of carbohydrate by colonic bacteria Withnormal digestion, typically the main source of fer-mentable carbohydrate is dietary FIBER, plant cellwall materials, and undigested starch Short-chainfatty acids include ACETIC ACID(acetate, a two-car-bon acid); PROPIONIC ACID(propionate, a three-car-bon acid); and BUTYRIC ACID (butyrate, afour-carbon acid)

Short-chain fatty acids are readily absorbed bythe colon and can be considered a major factor inhuman energy metabolism It is estimated thatshort-chain fatty acids produced by colonic bacteriacan satisfy 5 percent to 10 percent of the body’senergy needs Acetic acid and propionic acid areused by the liver, while butyric acid is a preferredfuel by cells lining the gut Indeed, butyrate is a pri-mary energy source for these cells In addition,butyrate helps guide the development and mainte-nance of colonic cells and may decrease suscepti-bility to colon CANCERand colitis

More than usual amounts of fermentable hydrate enter the colon with high-fiber diets andduring carbohydrate MALABSORPTIONand maldiges-tion, leading to increased production of short-chainfatty acids The production of short-chain fatty acidslowers intestinal ammonia levels liberated throughbacterial metabolism and limits the uptake of thiswaste product Ammonia can induce abnormalities

carbo-in carbo-intestcarbo-inal cells Short-chacarbo-in fatty acids also carbo-inhibitthe growth of certain pathogenic species like salmo-nella, and the resulting lowered colonic pH(increased acidity) favors VITAMIN K absorption,MUCUSsecretion, and magnesium uptake (See alsoFAT METABOLISM; INTESTINAL FLORA.)

580 sherbet

shortening A FATadded to a food item to keep it

soft during baking By dispersing fat droplets

throughout a dough, starch and grain protein do

not congeal into a compact mass when cooked

BUTTER (milk fat), LARD (pork fat), and TALLOW

(beef fat) are traditional shortening agents

Veg-etable shortenings contain hydrogenated vegVeg-etable

oils These are solids, unlike the original oils They

are prepared from hydrogenated oils with varying

melting points, and with varying degrees of

soft-ness Vegetable shortening is often prepared from

CORN OIL, COTTONSEED OIL, OLIVE OIL, PEANUT oil,

PALM OIL, SAFFLOWERoil, SESAMEoil, or SOYBEANoil

Regardless of form, all fats and oils provide nine

calories per gram, more than twice as much as

derived from carbohydrate and protein (four

calo-ries per gram)

Shortening is used for biscuits, bread, cookies,

and pie crusts The amount of shortening varies

with the recipe Bread and rolls contain 1 percent

to 2 percent shortening; cakes, 10 percent to 20

percent, and pastries, 30 percent When

shorten-ings are used for baking mixes, whipped topping,

icing, and filling, various emulsifying agents are

included These include MONOGLYCERIDES (glycerol

with only one fatty acid) Emulsifiers allow water

to be mixed with the shortening without

separa-tion (See also DIETARY GUIDELINES FOR AMERICANS;

FAT METABOLISM; VEGETABLE OIL.)

shrimp A type of SHELLFISH with 10 legs that

range in size from 0.5 in to several inches When

cooked, shrimp turn red due to a chemical change

in the shell pigment Typically, the parts of cooked

shrimp sold at markets are the abdominal region

and tail parts, after the heads have been removed

Shrimp is a high-protein food that is also a good

source of CALCIUM Shrimp contains somewhat

higher than usual levels of cholesterol, though less

than found in eggs Shrimp can be canned,

con-verted to shrimp paste, breaded and fried, or

stir-fried The nutrient content of 3.5 oz (100 g) is: 109

calories; protein, 23.8 g; fat, 1.5 g; cholesterol, 152

mg; calcium, 320 mg; iron, 2.2 mg; thiamin, 0.03

mg; riboflavin, 0.03 mg; niacin, 3.7 mg

silicon The second most common element on the

surface of the Earth and widely found in plants and

water Silicon is also found in the skin, BONE, andconnective tissue of animals It is an essential nutri-ent in animals, required for normal skeletal devel-opment of rats and chicks, for example It seemsprobable that silicon is essential for humans,although this remains to be established No RECOM-MENDED DIETARY ALLOWANCE has been establishedfor silicon Silicon participates in the formation ofconnective tissue where it forms complexesbetween protein and acidic polysaccharide com-plexes Acidic polysaccharides (GLYCOSAMINOGLY-CANS) contribute to the gelatinous material thatholds cells together In humans, the silicon content

of the aorta, the skin, and the thymus decreaseswith age

Silicon is widely distributed in whole grains,organ meats like liver, and red meat Most of thesilicon of whole grains is lost when white flour

is prepared, and highly processed foods contain tle silicon The typical diet supplies approximately

lit-1 g per day Within the confines of the typical diet, silicon is nontoxic (See also SKELETON; TRACE MINERAL.)

simple carbohydrate See CARBOHYDRATE

single-cell protein Food PROTEIN derived fromcultured bacteria, YEAST, fungi, and algae Algae(seaweed) has long been used as food Brewer’syeast, a by-product of the brewing industry, andTORULA YEAST are widely available food supple-ments The potential of cultured microorganismsserving as an edible protein source is huge A single-cell fermenter covering 0.8 sq km (one-third

of a square mile) could theoretically supply 10 cent of the protein requirement of the world’s population By-products of the food, paper, andchemical industry can be fermented by many mic-roorganisms as inexpensive energy sources Theseinclude methane, ALCOHOL, STARCH, MOLASSES, cel-lulose, and animal waste products Even fewerrequirements are needed for algae; photosyntheticorganisms can be grown in illuminated ponds sup-plied with mineral nutrients

per-Problems associated with single-cell proteinhave limited its development as a major foodsource Most single-cell protein is not palatableunless processed to eliminate bitter or unpleasant

single-cell protein 581

tasting materials Digestibility of single-cell protein

varies with the sources Cooking algae increases its

digestibility, but the digestibility of yeast is little

altered by processing The high nucleic acid content

of single-cell organisms leads to increased purine

uptake When purines are metabolized, uric acid

output rises and increases the risk of GOUT in

sus-ceptible people Furthermore, toxic materials and

pollutants can contaminate single-cell protein

Another consideration is the fact that single-cell

protein is generally deficient in the dietary essential

AMINO ACIDS, LYSINE, and METHIONINE Though the

amino acid profile is more balanced than in cereal

grain protein it remains inferior to animal protein

Genetically engineered microorganisms may

over-come this deficiency (See also FOOD CHAIN; HUNGER;

MEAT; PHOTOSYNTHESIS.)

skeleton The collection of bones that provides

the framework and protective covering for many

organs of the body including the brain, heart, and

spinal cord Unlike the NERVOUS SYSTEM, the

IMMUNE SYSTEMor the ENDOCRINE SYSTEM, the

skele-tal system plays a passive role in maintaining

nor-mal body function (HOMEOSTASIS) The skeletal

system protects internal organs; vertebrae protect

the spinal column; the cranium, the brain; the rib

cage, the heart, and the lungs; the pelvic bones, the

reproductive organs Bones store calcium and

phosphorus, which can be released and distributed

to other parts of the body via the bloodstream Red

bone marrow in certain bones yields blood cells;

RED BLOOD CELLS, some white cells and blood

PLATELETSrequired for blood clotting Fat in bone

marrow represents stored ENERGY The human

skeleton contains 206 bones and is held together by

tough connective tissue and cartilage Skeletal

muscles adhere to bones via tendons to promote

movement

Bones range in size from the robust femur to the

delicate, intricate bones of the wrist and ankle

Physical growth during maturation from infancy to

adulthood entails a dramatic increase in bone mass

and size Nearly 67 percent of bone represents a

mineral matrix, the compound calcium phosphate,

composed of the nutrients CALCIUMand PHOSPHO

-RUS Many other nutrients are required in the

growth and maintenance of the skeletal system

MAGNESIUMand FLUORIDEare also complexed withcalcium phosphate to help harden the bone matrix.BORON may reduce calcium and magnesium losses from bone in post-menopausal women Theskeleton requires a healthy connective tissue MAN-GANESE is required for the formation of muco-polysaccharides, while COPPER and VITAMIN C arerequired for the formation of COLLAGEN andELASTIN, proteins of connective tissue and tendon,respectively Bone-forming cells are maintained byVITAMIN A among other nutrients VITAMIN D,together with ample calcium, phosphorus, andmagnesium, promotes normal skeletal develop-ment and prevents RICKETS in children In adults,vitamin D prevents bone thinning and softening.(See also OSTEOMALACIA; OSTEOPOROSIS.)

skim milk See MILK

skin The outer surface of the body and its largestorgan The skin of an adult covers a surface area of

2 square meters and forms the primary physicalbarrier to the external environment, bacteria, andother microorganisms The skin also helps regulatebody temperature through heat lost by the evapo-ration of sweat and by changes in blood flow to theskin A limited amount of body wastes and chemi-cal toxic load can also be eliminated through sweat.The skin supports the sense of touch via sensorynerve endings embedded there These nerves react

to temperature, pressure, pain, and touch The skin

is responsible for synthesizing vitamin D3 from astored precursor when exposed to ultraviolet light.Finally, certain types of cells embedded in underly-ing layers are important components of immunity,the ability to ward off disease

Nutrient Support

The chief constituent of the skin is COLLAGEN, astructural protein requiring vitamin C Collagenand ELASTIN are fibers of connective tissue thatkeep the skin smooth and toned VITAMIN C andCOPPERare trace nutrients that support the synthe-sis of elastin proteins Vitamin C and VITAMIN Etogether with SELENIUMare required for a healthyskin They are powerful scavengers of FREE RADI-CALS, the highly reactive chemicals formed by sun-light and oxygen, smog, pollutants, and other

582 skeleton

factors Essential fatty acids, LINOLEIC ACID and

ALPHA LINOLENIC ACID, which occur in seed oils, are

important in maintaining a lustrous skin

Seba-ceous glands secrete an oily material called sebum,

which is a mixture of oils, cholesterol, protein, and

inorganic salts This oily film protects hair and skin

from drying out; prevents excessive evaporation

from the skin; keeps the skin soft and pliable; and

blocks the growth of certain bacteria It forms a

water-impermeable barrier and prevents the skin

from becoming saturated with water

AGING brings marked changes in the skin The

skin appears rougher, drier, and thinner, and the

cushioning layer of fat beneath the skin

dimin-ishes There are fewer melanocytes, cells that

pro-duce pigment to protect against sunlight’s

ultraviolet damage, and there is less collagen and

elastin and that which remains may be damaged

All structures in the skin can be affected by

chronic exposure to U.V light U.V light reacts with

cells by initiating free radical reactions Free

radi-cals attack cells and damage their DNA, which

accounts for most skin damage Sunburn is an

injury to the skin due to ultraviolet rays that may

lead to cell death and mutations The skin becomes

leathery, with wrinkles, lines, sagging skin areas,

wart-like or scaly precancerous growths, yellow

discoloration, and abnormal elastic tissue

The first line of IMMUNE SYSTEM defense in the

skin are Langerhans cells These sentries can detect

the intrusion of foreign materials and quickly

sig-nal other components of the immune system to

counterattack U.V light whether from tanning

parlors or from sunlight suppresses these cells

Photosensitivity can aggravate the reaction to

the sun’s rays Certain foods (citrus fruits, for

example), deodorant soaps, Retin-A, antibiotics,

tranquilizers, and DIURETICS (water pills) contain

materials that can accentuate a reaction to sunlight

such as burning and development of age spots By

minimizing ultraviolet exposure, new connective

tissue can replace the old with adequate nutrition

Vitamin E, vitamin C, and B complex vitamins

promote repair and cellular growth These

antioxi-dants also function as an anti-inflammatory agents

that aid in the repair of cell damage Flaxseed oil,

borage oil, and EVENING PRIMROSE OIL provide

essential fatty acids also needed for skin

mainte-nance COLLAGEN has a moisturizing effect whenapplied in skin lotion, but it is not absorbed or used

by the skin when applied topically Whether theskin can be nourished by external vitamin applica-tion remains unclear Manufacturers often addantioxidants to skin lotions, and there is some evi-dence that fat-soluble vitamins and other oily(lipophilic) derivatives of vitamins do penetrate theskin A 2 percent to 10 percent concentration ofthese substances may be needed to be effective;often, skin preparations contain low amounts.Some manufacturers incorporate materials in lipo-somes, microscopic sacs prepared from lipids, to aidthe absorption of a variety of substances Prepara-tion of microscopic droplets (called micelles) alsohelps materials penetrate the upper dead layers ofskin to reach cells of the dermis (See also ACNE.)

Xue, L “Influence of Dietary Calcium and Vitamin D on Diet-Induced Epithelial Cell Hyperproliferation in

Mice,” Journal of the National Cancer Institute 91 (1991):

176–181.

skin fold test See FAT FOLD TEST

skin test See ALLERGY, FOOD

small intestine (small bowel) The tube extendingfrom the stomach to the large intestine (COLON).Typically, the small intestine is 1 in (2.5 cm) indiameter and 21 ft (6.35 m) long It is divided intothree regions; the first 10 inches is called the DUO-DENUM; the JEJUNUMrepresents the next 8 feet; andthe ILEUM occupies the lower reaches of the smallintestine The intestine carries out two distinct func-tions: It selectively absorbs nutrients and importantmaterials from food and beverages, and at the sametime, it excludes a vast amount of foreign sub-stances, ranging from microorganisms and food par-ticles to pollutants and bacterial by-products Tocarry out its absorptive function, the surface ishighly convoluted and is covered with small projec-tions about 1 mm high, called VILLI, giving it a vel-vet appearance Within each villus is a capillarynetwork and lymphatic vessel to aid the uptake anddistribution of nutrients The surfaces of villi arelined with absorptive cells; each cell possesses manymicroscopic projections called microvilli The num-

small intestine 583

ber of villi decreases in the ileum; most absorption

occurs in the duodenum and jejunum The total

surface area of the intestine is huge If the microvilli

and villi were flattened out, the surface would be

about the size of a tennis court

The small intestine is the major site of DIGESTION

Pancreatic enzymes efficiently digest fat, protein,

and starch The intestinal lining secretes fluid

(intestinal juice) containing electrolytes (ions) and

mucus to protect the wall of the intestine from

digestive enzymes The volume is substantial The

small intestine secretes two to three liters of juice

per day Most of the ions and water are reabsorbed

and recycled

Intestinal enzymes complete the final stages of

digestion They include MALTASEto digest maltose,

the sugar released from starch digestion; SUCRASEto

digest SUCROSE(table sugar); and LACTASEto digest

LACTOSE (milk sugar) A milk intolerance often

reflects LACTOSE INTOLERANCE that is an impaired

ability to digest lactose due to inadequate lactase

Undigested lactose passes on to the colon where

bacteria rapidly ferment it, often producing gas,

bloating, and diarrhea The small intestine also

pro-duces peptidases to degrade small protein

frag-ments to amino acids

Partially digested food (chyme) moves down the

intestine by localized muscle contraction, creating a

mixing action PERISTALSIS refers to the wave-like

contractions moving down the gastrointestinal

tract Chyme moves at the rate of 1 cm/min;

con-sequently, food remains in the small intestine three

to five hours The small intestine produces an array

of hormones to regulate digestion CHOLECYS

-TOKININstimulates contraction of the gallbladder to

release bile, and it stimulates pancreatic enzyme

secretion SECRETIN reduces gastric and duodenal

motility and promotes bicarbonate secretion by the

pancreas Gastric inhibitory protein blocks stomach

acid release, while stimulating insulin secretion To

exclude foreigners, the intestine maintains a

phys-ical barrier The mucus coating is constantly being

replaced as it is washed away, limiting penetration

Underlying cells are tightly bonded together to

limit the leakage of unwanted substances into the

body The movement of food through the digestive

tract and the presence of powerful digestive

enzymes limit uptake of foreign materials The

major immune barrier is a secreted antibody called

secretory IgA This defensive protein is secreted byimmune cells embedded within the intestinal walland can bind to specific antigens (foreign sub-stances) and prevent their adhering to the intesti-nal surface Like all antibodies, specific types of IgAare produced against specific antigens

Cells lining the intestine replenish themselves inone to two days, thus the nutrient needs of thisrapidly dividing tissue are unusually high Amplezinc and the B complex vitamins, especially FOLIC ACID, are essential for maintaining a healthy intes-tine GLUTAMINE helps maintain enterocytes, theepithelial cells lining the small intestine, whilebutyrate (BUTYRIC ACID) is essential for the help ofcolonocytes, lining the colon

If the intestine become inflamed, it can becomemore “leaky” and foreign substances can enter thebody The influx of foreign materials can triggermultiple food allergies, joint pain, skin conditions,and autoimmune disease in which the body’sdefenses attack itself LEAKY GUT syndrome can becaused by alcoholism, overuse of pain medication(nonsteroidal anti-inflammatory drugs), inadequatepancreatic output, infection, AIDS, or Crohn’s dis-ease (ulcerated small intestine), among others Withchronic constipation, low stomach acid and aging,colon bacteria may creep upward into the smallintestine, leading to a condition known as bacterialovergrowth of the small bowel Symptoms includesensitivity to starchy food and refined carbohy-drate—leading to bloating, gas, diarrhea and otherdiscomfort Bacterial overgrowth often leads tomaldigestion and to malabsorption of vitamins,such as VITAMIN B12 Eradicating the offending bac-teria, while remedying the underlying cause,together with dietary modification can alleviate thiscondition (See also AMINO ACID METABOLISM; CAR-BOHYDRATE METABOLISM; FAT METABOLISM.)

smell The olfactory sense and one of the five basicsenses Smell is a chemical sense, providing a directlink with the environment It evolved primarily todetermine which substances are acceptable Whenmolecules escape into the air, they travel up thenose to a small region of moist tissue called theolfactory membrane The sense of smell relies onthe binding of volatile (gaseous) compounds to cellmembranes Gaseous compounds penetrate themucus covering the olfactory cells and bind to hair-

584 smell

like extension (cilia) like tassels Signals are sent

along a nerve to olfactory bulbs at the base of the

brain, where they radiate out to regions of the brain

concerned with mood, strong emotions, memory,

and thought There are about 1,000 different

recep-tors or docking sites that are able to recognize some

10,000 different odors Flavors of foods are often

based on odors rather than mouth (taste)

sensa-tions Unique flavors usually reflect a combination

of smell and TASTE When foods are placed in the

mouth, odor molecules travel to the olfactory

neu-rons up the passage linking the inside of the nose

and throat A serious loss of smell affects about two

million Americans (a condition known as anosmia)

Most commonly this is a result of allergies, certain

medications, and head injury

Axel, Richard “The Molecular Logic of Smell,” Scientific

American 273 (October 1995): 154–159.

sodium The major positively charged ion in body

fluids Due to their chemical nature, metallic

ele-ments such as sodium exist in solutions and in

compounds as cations, positively charged ions,

where they counterbalance negatively charged

ions, such as CHLORIDE Sodium, therefore,

func-tions in maintaining ELECTROLYTE balance, that is,

the balance between negatively and positively

charged ions and among complex ions such as

pro-teins in the blood Sodium predominates in the

extracellular fluid, while POTASSIUM, another

cation, concentrates within cells Normally,

chlo-ride and sodium tends to leak into cells, while

potassium tends to leak out Sodium is pumped out

of cells, while potassium is pumped inward by

means of an energy-dependent process called

“active transport.” Maintaining normal cell volume

(and shape) depends on sodium and potassium

pumping The active transport of sodium and

potassium is a predominant energy-consuming

process of the cells, accounting for a large

percent-age of the total energy expenditure of the body

Sodium plays a vital role in controlling osmotic

pressure, the pressure that develops between the

blood and cells due to ionic concentration

differ-ences The total volume of extracellular fluid is

determined by its sodium level, which the body

maintains under tight control by means of the

endocrine and nervous systems By balancing

charges of negatively charged ions like chloride,BICARBONATE and phosphate, sodium assists inmaintaining the proper balance between acidic andalkaline substances (acid-base balance)

Sodium works with potassium in nerve tion To transmit a nerve impulse, the nerve cellmembrane is temporarily “depolarized”; potassiumtemporarily leaks outside and sodium and chlorideleak in This generates a decrease in electrical po-tential, which triggers a voltage-dependent in-crease in sodium penetration Restoration of thepotential differences to the resting state allows theimpulse to be transmitted as a self-propagatingwave down a nerve cell Muscles, especially heartmuscles, require an interplay of sodium and potas-sium by similar mechanisms

func-The kidney normally reabsorbs sodium that wasfiltered out into the urine to maintain electrolytebalance Water follows sodium back into the blood,thus hormones that increase sodium retention bythe kidney also increase water retention Sodiumconcentration and water balance are controlled by

an interplay of the kidney and several hormones:When the level of sodium drops, the enzyme RENIN

is released by the kidney Renin catalyzes the version of a blood protein to ANGIOTENSIN In turn,this hormone stimulates the adrenal gland torelease ALDOSTERONE, a hormone that causes thekidney to increase the rate of sodium reabsorptionfrom filtered fluid to correct the original sodiumdepletion On the other hand, when dietarysodium intake is high, the kidney rapidly excretessodium Through the operation of these homeosta-tic (body balancing) mechanisms, the amount ofsodium excreted is adjusted to equal the amountconsumed Ninety percent of ingested sodium isexcreted; some is lost through sweat and feces.Excessive sodium intake and retention can causeswelling (EDEMA)

con-Sources

Most vegetables, fruits, and legumes contain onlylow levels of sodium, unless pickled Although theU.S FDAestimates that processed food contributes

25 percent to 50 percent of the sodium in the ical U.S diet, other studies of sample diets indicatethat an estimate of 60 percent to 75 percent is morerealistic Ninety percent of dietary sodium comesfrom sodium chloride (table salt); only 15 percent

typ-sodium 585

of dietary sodium comes from the salt shaker.

There are several explanations for the prevalence

of sodium in foods Salt is a very inexpensive way

to flavor PROCESSED FOOD, in place of more

expen-sive herbs and spices Sometimes companies are

not aware of the sodium content in their products

The amount of sodium in the same type of food,

produced by different manufacturers, can differ by

50 percent to 300 percent Salt is also used in

recipes dating to a time when salt was not known

to be potentially harmful

The only way to detect salty food is by taste,

yet this is an unreliable indicator of sodium

con-tent For example, FRENCH FRIES may have only

one-quarter the amount of sodium in an equal

serving (weight) of cherry pie because sugar

masks the taste of salt Hidden salt occurs in

gelatin desserts, milk shakes, cheese, canned

soups, packaged and frozen dinners, and foods at

fast-food restaurants; in cured ham and bacon,

cured fish, corned beef, smoked herring, and soy

sauce Processed meat like BOLOGNA and HOT

DOGS, tomato KETCHUP, many cold BREAKFAST

CEREALS, pickled foods, and salad dressings

pro-vide high levels of sodium Sodium occurs in

other food additives such as baking soda and

sodium aluminum sulfate (in baked goods),

sodium caseinate (a milk product), sodium

phos-phate (the major contributor of sodium in

cheese), sodium nitrite and sodium benzoate

(preservatives), and MONOSODIUM GLUTAMATE

(fla-vor enhancer) LAXATIVES and ANTACIDS can

account for a large percentage of sodium for some

people, especially elderly persons Human milk

contains 161 mg of sodium per liter, while cow’s

milk provides 483 mg per liter; therefore, cow’s

milk provides considerably more sodium

Soft water contains high levels of sodium The

amount depends upon the hardness of natural

water A glass of tap water usually contains less than

3 mg of sodium However, salt from the de-icing of

roads and ion exchange resins can raise sodium

levels in inland areas Sodium from seawater can

leach into the water supplies of coastal areas

Requirements

There is no RECOMMENDED DIETARY ALLOWANCE

(RDA) for sodium A safe and adequate level was

proposed by the Food and Nutrition Board as1,100 to 3,300 mg per day in 1980 The 1989 RDArecommendations list the minimum requirementsfor healthy persons (adults 18 or older) as 500 mg

of sodium daily The sodium requirements ofinfants and small children are estimated to beabout 58 mg daily The amount of sodiumrequired to maintain sodium equilibrium for mostadults may be less than 200 mg under normal cir-cumstances, equivalent to one-tenth a teaspoon ofsalt per day The overall consensus is that Ameri-cans generally consume too much salt The typicaladult intake is 6 g to 25 g of salt, with a mean of

10 g/day, equivalent to 4 g of sodium, 20 times asmuch as the listed minimum The maximum rec-ommended daily intake of sodium chloride is 6 g(2.4 g)

Few people in the United States are sodium cient Relatively heavy sweating is now associatedwith a need for extra salt, and the primary concernshould be fluid replacement Athletes undergoingstrenuous physical exercise do not need salt untilthey have lost approximately three quarts of water

defi-by sweating The kidney adapts to sodium losses inhot weather, so that less sodium, hence less water,

is excreted One typical meal will more than make

up for sodium lost in sweat through moderateexercise Chronic diarrhea, kidney disease, or othermedical conditions can limit the body’s ability toretain sodium and thus increase sodium require-ments Excessive sodium can be toxic to infantsbecause their kidneys are not fully developed; itmay also be toxic to those with kidney disease orthose who have adjusted to a chronically low-sodium diet

Sodium and High Blood Pressure

Sodium has been linked to high blood pressure(HYPERTENSION) in extensive studies spanningdecades Perhaps 10 percent to 20 percent of Amer-icans experience increased blood pressure whenthey eat excess sodium High blood pressureincreases the risk of STROKE, HEART ATTACK, and kid-ney disease Worldwide, a low sodium intakematches a lowered risk of hypertension CertainlyOBESITY, genetic makeup, lack of exercise, andexcessive alcohol are risk factor for developinghypertension Salt sensitivity increases with age As

586 sodium

people grow older, their kidneys excrete less

sodium, and an increased sodium intake is more

likely to raise blood pressure in susceptible people

Cutting back on salt intake may lower blood

pres-sure by a small amount; however, even relatively

small decreases in blood pressure readings could

mean a significant decreases in the risk of death

due to coronary heart disease Excessive sodium

increases urinary losses of calcium and can

con-tribute to the risk of osteoporosis Additionally, a

high-salt diet is a dominant risk factor for stomach

cancer Governmental dietary guidelines

recom-mend moderate sodium consumption, and

individ-uals with hypertension or who have a family

history of hypertension may be advised to curtail

sodium consumption

To cut back on salt, do not add salt to foods

Sea-son with herbs or sauces instead Cut back on

processed, convenience foods Read food labels to

determine the sodium content and avoid foods

with high sodium Do not take salt tablets without

consulting a doctor Reducing high blood pressure

can mean, in addition to cutting back on sodium,

limiting alcohol consumption to one or two drinks

per day; engaging in regular aerobic exercise;

get-ting enough calcium, potassium, and magnesium;

and losing weight

Sodium on Food Labels

Sodium must be listed on the label of any foods

that list nutritional content, and on those that

make nutritional claims as being “low fat” or

“enriched.” (Exempt foods are those made with

• “Reduced sodium” means the food has been

processed to reduce normal sodium levels by at

least 75 percent

• “No sodium” and “no salt” alternatives: Several

cold breakfast cereals, canned vegetables, and

herbal salt substitutes have been introduced to

meet consumer demands

SODIUM CONTENT OF COMMON FOODS Food Sodium (mg) per 100 g (3 oz.)

(See also FOOD ADDITIVES; MINERALS.)

sodium alginate See ALGINATE

sodium ascorbate See VITAMIN C

sodium benzoate A food preservative thatretards growth of microorganisms under acidicconditions Foods and beverages can contain up to0.1 percent sodium benzoate Soft drinks, saladdressing, and fruit juices often contain this preser-vative Sodium benzoate also occurs naturally invegetables and fruit, for example, in prunes andcranberries Sodium benzoate is a product ofmetabolism as well Extensive studies indicate it is

a safe additive

sodium chloride See SODIUM

sodium erythroborate See ERYTHROBORIC ACID

sodium nitrate See NITRATE

sodium nitrite See NITRITE

soft drinks Carbonated, nonalcoholic beveragesthat contain dissolved CARBON DIOXIDE (carbona-tion), sweeteners, flavoring agents, edible acids,and food coloring Soft drink consumption in theUnited States has doubled since 1974 Increasedsoft drink consumption means increased consump-tion of PHOSPHOROUS, ARTIFICIAL FOOD COLORS, andARTIFICIAL SWEETENERS, and sugar In contrast,water contains none of these additives

soft drinks 587