The Encyclopedia Of Nutrition And Good Health - V docx

Whole grains, seafood, milk products, and meat are fair sources, while beverages, vegetables, and fruits contain the lowest amounts.. A high protein diet also increases blood flow in the

639

valerian root (Valerian officinalis; garden

helio-trope; setwall) The root of a perennial herb native

to Europe, North America, and northern Asia that

has been used as a sleep aid and antianxiety

treat-ment for more than 1,000 years The plant is

inconspicuous except for its small white or pink

flowers and an unusual odor that some have

described as reminiscent of aged cheese According

to legend, the Pied Piper used valerian to lure rats

from the village of Hamelin

Valerian is a popular dietary supplement in the

United States and in Europe whose supporters

claim it has a calming effect and can induce sleep

Reliable research to support these claims does

not yet exist, but the herb does appear to have

some effect on the neurotransmitter

gamma-aminobutyric acid (GABA) Small studies suggest

effectiveness in promoting sleep compared to

placebo People with nerve disorders that causes

uncontrollable spasms or who suffer from TARDIVE

DYSKINESIAhave been found to have low levels of

GABA in their brains Because of the herb’s

repu-tation as an antispasmodic, it has been used for

centuries by women seeking relief from menstrual

cramps As a food, valerian is classified “generally

recognized as safe.”

Because valerian root is available in the United

States as an herb, its safety and efficacy have not

been tested by the U.S Food and Drug

Administra-tion (FDA) However, in high doses valerian root

rarely can cause liver damage with long-term use

or high doses Some patients who have taken the

supplements have suffered chest pain, heart

arrhythmia, tremors, insomnia, headache, and

blurred vision With long-term high doses,

sud-denly stopping valerian may be associated with a

withdrawal syndrome A few reports suggest

possi-ble decreased alertness after valerian use Women

who are pregnant or nursing should not take thissupplement due to inadequate safety data

Garges, P et al “Cardiac Complications and Delirium

Associated with Valerian Root Withdrawal,” Journal of

the American Medical Association 280 (November 1998):

1,566–1,567.

valine (Val, L-valine) A dietary essential AMINO ACID that serves as an important protein buildingblock Valine is classified as a BRANCHED CHAIN AMINO ACID, along with ISOLEUCINE and LEUCINE.The daily requirement for valine is estimated to be

10 mg per kilograms of body weight, similar to theother branched chain amino acids Infusedbranched chain amino acids are selectively used forenergy by skeletal muscle rather than by the LIVER.Branched chain amino acids may help restore mus-cles in patients with liver disease or in patients whohave undergone physical trauma such as surgery.However, it is not established that these aminoacids have an anabolic (muscle enhancing) effectwhen used as supplements for healthy people.Valine and other branched chain amino acidsare useful in treating liver damage associated with

ALCOHOLISM (hepatic encephalopathy) They seem

to limit muscle wasting and reduce some of theneurologic effects related to this disease Valine andbranched chain amino acids may be useful in treat-ing amyotrophic lateral sclerosis (Lou Gehrig’s dis-ease) Levels of these amino acids are low in thesepatients On the other hand, animal studies indi-cate that an excess of one branched chain aminoacid antagonizes the other two (See also AMINO ACID METABOLISM.)

vanadium A TRACE MINERALrequired by animalsfor normal growth and development Deprivation

of this element causes slowed growth, reproductive

problems and blood abnormalities in rats and

chicks Vanadium in the form of vanadate and

vanadyl sulfate improves the effect of insulin in

diabetic animals; and artificially induced diabetes

in rats can be reversed by vanadate Large doses

also affect serum FAT and CHOLESTEROL levels,

although more research in this area is needed

There is no RECOMMENDED DIETARY ALLOWANCE

for vanadium, and the amounts required for

opti-mal health are unknown Nutritional requirements

would likely be met by levels present in food Black

pepper and dill seeds are the richest sources Whole

grains, seafood, milk products, and meat are fair

sources, while beverages, vegetables, and fruits

contain the lowest amounts The average daily

intake in the United States is about 20 mcg, quite

low in comparison to known essential trace

ele-ments Elevated vanadium is associated with

bipo-lar disorder, and high levels of vanadium may be

toxic

vanilla (Vanilla planifolia) A tropical plant that

produces pods containing vanilla, an aromatic

ingredient used as a food flavoring Vanilla is a

member of a group of tropical orchids, native to

Central America and Mexico The active

ingredi-ent, ethyl vanillin, is chemically synthesized and

marketed as “vanillin.” Ethyl vanillin has 3.5 times

the flavor intensity of vanilla bean extract Because

it lacks minor ingredients found in the extract, the

taste is not identical Vanilla is used to flavor ice

cream, beverages, chocolate, candy, and gelatin

Vanilla is considered a safe additive (See also FLA

-VORS; FOOD ADDITIVES.)

variant Creutzfeldt-Jakob disease (vCJD) See

BEEF

varicose veins Bulging, sinuous veins that are

close to the surface of the skin Usually the term

varicose veins refers to distended leg veins in which

blood vessels become weakened, permitting blood

to flow backward instead of forward to the heart

This condition affects an estimated 25 percent of

American women, 10 percent of men, and 50

per-cent of people over the age of 50 Often, varicose

veins are only a cosmetic issue with no symptoms.However, symptoms like aching legs can developafter a person has been standing for a long time.Leg cramps, swollen ankles, intense pain or tender-ness along the vein at the end of the day can occur.Occupations that require extended periods ofstanding increase the risk of varicose leg veins.Pregnancy also increases venous pressure in thelegs and may lead to the development of varicoseveins Standing places heavy pressure against legveins, and the extra weight of the blood stretchesthe walls of the vessels, which pulls apart vesselvalves, causing blood to pool in the veins Thispressure can cause surface vein walls to bulge outinto varicose veins

Varicose veins can occur anywhere in the body.Hemorrhoids are a common example; they can beaggravated in straining during bowel movementsbecause intense abdominal pressure is transmitted

to all veins, even leg veins Defective, deeper veinscan become inflamed (phlebitis) and create a bloodclot, resulting in a more serious condition If theclot dislodges, it can cause blockage in vessels of thelung, the heart (HEART ATTACKor myocardial infarc-tion), or the brain (STROKE)

In addition to inheritance, lifestyle and diet arebelieved to be predominant factors in the develop-ment of varicose veins They seldom occur in pop-ulations relying on a diet high in unrefined,fiber-rich foods EXERCISEsuch as walking and bikeriding contract leg muscles that push blood alongthe venous system Increasing the strength of ves-sel walls may minimize the risk of varicose veins.Blue-red berry pigments called anthocyanidins andproanthocyanins can strengthen vessel walls,reduce capillary fragility and help protect thevenous connective tissue BLACKBERRIES, CHERRIES,and BLUEBERRIESare rich sources People who havevaricose veins may also be less able to break down

FIBRIN, a clotting protein that is often depositednear varicose veins and increases the risk of clotformation CAPSICUM (cayenne pepper), GINGER,

GARLIC, and ONIONSincrease fibrin breakdown (Seealso CIRCULATORY SYSTEM; DIET, HIGH COMPLEX CAR-

BOHYDRATE; FIBER.)

vasoconstriction Reducing the diameter ofblood vessels Both environmental and physio-

640 vanilla

logic factors can constrict vessels For example, a

drop in temperature causes vasoconstriction, an

adaptation that helps conserve body heat All

blood vessels except capillaries and venules are

regulated by the NERVOUS SYSTEM Thus fear and

other emotions can reduce blood flow At wound

sites, SEROTONIN and other products are liberated

by blood PLATELETS, cells that stick to the walls of

damaged vessels to form clots Serotonin helps

reduce blood loss by acting as a vasoconstrictor

Certain hormones act as vasoconstrictors: EPINEPH

-RINEand norepinephrine (released by the ADRENAL

GLANDS in response to stress) and ANGIOTENSIN II

(formed in the KIDNEYS in response to a drop in

blood pressure)

vasodilation Increasing the diameter of blood

vessels Vasodilation increases blood flow and

removes waste products while replenishing oxygen

and nutrients Decreased oxygen concentration

and the accumulation of metabolic waste products

help expand blood vessel walls The accumulation

of LACTIC ACID, decreased pH (more acidic blood),

the buildup of carbon dioxide, and increased blood

ion concentration (osmolarity) dilate blood vessels

Increased body temperature exerts a vasodilator

effect to help cool the body During inflammation,

HISTAMINEis released from damaged cells and from

immune cells called mast cells Histamine is known

to increase capillary leakiness, and fluid leakage

out of capillaries accounts for swelling in areas of

inflammation

An important family of vasodilators is the

kinins, which represent peptides, whose parents

occur in the blood and in tissues Kinins resemble

histamine: They relax the smooth muscles around

vessels and increase capillary leakiness and blood

flow through the kidneys Kinins occur in sweat

glands, salivary glands, and the PANCREAS Kinin

release is inhibited by GLUCOCORTICOIDS, hormones

produced by the adrenal glands A high protein diet

also increases blood flow in the kidneys PROS

-TAGLANDINS, hormone-like substances made from

essential fatty acids, can have similar effects (See

also EDEMA; NITRIC OXIDE.)

vasopressin See ANTIDIURETIC HORMONE

veal BEEFfrom male dairy calves, ranging in agefrom four to 18 weeks Subtherapeutic doses ofdrugs may be used when veal calves are very young;this treatment is discontinued as the animal’simmune system matures Veal, like most red MEAT,

is a good source of ZINC and other trace minerals.The nutrient content of a 3-oz (85 g) braised vealcutlet is: 185 calories; protein, 23 g; fat, 9.4 g; cho-lesterol, 109 mg; calcium, 9 mg; iron, 0.8 mg; thi-amin, 0.06 mg; riboflavin, 0.21 mg; niacin, 4.6 mg

vegan See VEGETARIAN

vegetable oil Edible oil extracted from seeds ornuts Plant oils provide ENERGY, VITAMIN E, andpolyunsaturated FATTY ACIDS No vegetable oil con-tains CHOLESTEROLbecause plants do not synthesize

it Vegetable oils classified as TRIGLYCERIDES; likeanimal FAT, they contain three fatty acids and GLYC-

EROL(glycerin) and contain just as many calories asanimal fat (nine calories per gram)

Vegetable oils fall into three classes: saturated,monounsaturated, and polyunsaturated:

1 Saturated vegetable oils are solid at room perature The so-called TROPICAL OILS, palm ker-nel oil and COCONUT OIL, and VEGETABLE SHORTENING, a chemically hardened vegetablefat, are saturated and are solids at room temper-atures These saturated fats resemble saturatedanimal fat, as in LARD, BUTTERFAT, and beef TAL-

tem-LOW The excessive consumption of SATURATED FATregardless of its source is believed to increasethe risk of CARDIOVASCULAR DISEASE

2 Monounsaturated oils including OLIVE OIL arerich in a fatty acid called OLEIC ACID, which lackstwo hydrogen atoms and contains a single dou-ble bond Olive oil apparently lowers blood

LOW-DENSITY LIPOPROTEIN (LDL) cholesterol, theless desirable form, without lowering the “good”kind of cholesterol HIGH-DENSITY LIPOPROTEIN

(HDL), and probably lowers the risk of vascular disease

cardio-3 Polyunsaturated oils such as CORN OIL, SAF

-FLOWERoil, SUNFLOWERoil, and SOYBEANoil tain a preponderance of polyunsaturated fattyacids These fat building blocks lack manyhydrogen atoms and contain two or more dou-

con-vegetable oil 641

ble bonds High consumption of

polyunsatu-rated vegetables oils apparently lowers LDL

cho-lesterol levels, a desirable result, but also lowers

HDL levels, which is undesirable High

con-sumption of polyunsaturated oils increases the

need for the antioxidant vitamin E

Extraction of Oils

The first step in oil extraction involves crushing or

grinding oil-bearing tissue to release oil from cells

The second step involves pressing to squeeze oil

from crushed tissue Residues from pressing are

usually extracted with solvents such as hexane to

remove the remaining oil The solvent is then

removed To purify these oils, they are further

extracted with alkali and heated, degummed,

deodorized by steam treatment, and decolorized by

treatment with charcoal or clay Since these

proce-dures remove or destroy vitamin E, synthetic

antioxidants like BHT, BHA, and PROPYL GALLATEare

often added to retard RANCIDITY Oils may be

“win-terized” by removing particulate matter that form

upon chilling

The assumption that cold-pressed oils have been

extracted from the seeds under mild conditions and

contain more vitamin E and polyunsaturated fatty

acids may not be valid Cold-pressed oils are often

heated between 120° F and 150° F, then refined,

bleached, and deodorized, processes that can

involve further heating, possibly at temperatures as

high as 450° F

Certain “unrefined oils” are available In the

preparation of these oils, processors do nothing to

the oils after heating ground seeds and pressing

them to extract the oils Because such oils are less

pure, they have distinctive flavors and colors

Hydrogenation

Unsaturated vegetable oils can be hardened and

stabilized by chemically adding hydrogen atoms to

reduce the degree of polyunsaturation

Hydrogena-tion increases the shelf-life of an oil by making it

more resistant to rancidity Heating vegetable oils

at high temperatures does not hydrogenate oils,

nor does it convert them to saturated fat “Partially

hydrogenated” vegetable oils retain some of their

polyunsaturated fatty acids and remain oils at room

temperature, while completely hydrogenated

(sat-urated) oils are solid at room temperature

(veg-etable shortening) Hydrogenated veg(veg-etable oils aswell as partially hydrogenated oils contain chemi-cally altered fatty acids called TRANS-FATTY ACIDS;their long-term safety has been questioned.Americans generally consume too much fat andoil, which increases the risk of HEART ATTACK,

STROKE, OBESITY, and certain forms of CANCER Aperson with high blood cholesterol may be advised

to reduce saturated fat intake Total fat shouldaccount for less than 30 percent of daily calories,perhaps as low as 20 percent of calories according

to some authorities To reduce the decompositionand rancidity of vegetable oils, store oils in therefrigerator in sealed dark containers Do not heatoils any more than is necessary and limit cookingwith oils at high temperatures Discard cooking oilsafter use

vegetables Cultivated plants that generally vide leaves, stems, roots, and flowers used as foods.Leafy vegetables include SPINACH, CHARD, CABBAGE,and LETTUCE Stem vegetables are CELERY and

pro-ASPARAGUS; BEETS, TURNIPS, YAMS, POTATOES, and

CARROTS are roots and tubers as opposed to stems.Vegetables like pumpkin, squash, BROCCOLI, and

CAULIFLOWER are flowers GARLIC and ONIONS arebulbs Corn is a seed vegetable Vegetables includeseveral botanical classes, including TOMATOES

(fruit); PEASand BEANS(legumes); and MUSHROOMS

CHOKE, asparagus, celery, chard, CHICKPEA,

ENDIVE, KALE, KOHLRABI, OLIVE, PARSLEY, PARSNIP

• Africa: the BROAD BEAN, CRESS, OKRA, yam; theMiddle East: broad bean, cabbage, carrot, cauli-flower, CUCUMBER, LENTIL, lettuce, mustardgreen, RADISH, SPINACH

• India: EGGPLANT, MUNG BEAN; China: Chinesecabbage, SOYBEAN, water chestnut

• Central Asia: beet, chive, carrot, DANDELION, lic, LEEK, onion, pea, shallot, turnip

gar-• Central America: bean, corn, jicama, green PEP

-PER, PUMPKIN, SQUASH, SWEET POTATO, tomato

642 vegetables

• South America: cassava, corn, lima bean, pepper

potato, sweet potato, tomato

Root vegetables and tubers like yams, sweet

potatoes, carrots, and potatoes are by far the

lead-ing vegetable crops They provide starch, fiber,

minerals, and some vitamins Orange-colored

veg-etables like sweet potato and carrot provide BETA

-CAROTENE Several of the most popular vegetables

in the United States provide minimal nutrient

con-tent: celery, lettuce, cucumbers The greener the

vegetable, the more the beta-carotene (provitamin

A) and CAROTENOIDS it contains Spinach, collard

greens, dandelion greens, kale, and Swiss chard are

excellent sources and they provide vitamin C, iron,

and calcium

The consumption of fresh vegetables in the

United States has steadily increased since 1980

from about 115 lb per person per year to over 190

lb per year (1990) Nonetheless, fewer than 10

percent to 20 percent of U.S citizens report eating

the minimum recommended five daily servings of

vegetables and fruits Potatoes represent nearly 37

percent of all fresh vegetables, and their popularity

accounts in part for this increased vegetable

con-sumption Much of this increase represents french

fries and baked potatoes eaten away from home;

french fries and baked potatoes with fatty sauces

are high-fat foods, in comparison with baked

pota-toes without toppings Lettuce, broccoli, tomapota-toes,

carrots, and cauliflower show increased popularity,

probably a reflection of the increased availability of

salad bars in fast-food restaurants

There is a growing awareness that vegetables

provide materials besides vitamins and minerals

that are important for long-term health Some

plant substances (PHYTOCHEMICALS) are not

consid-ered essential nutrients, yet their consumption can

have long-term effects on reducing the risk of CAR

-DIOVASCULAR DISEASES, CANCER, CATARACTS, AUTOIM

-MUNE DISEASESlike rheumatoid arthritis, premature

senility, and other chronic problems associated

with AGING Plants of the cabbage family, including

broccoli, cabbage, and brussels sprouts, produce

materials called ISOTHIOCYNATESand indoles, which

seem to lower the risk of cancer Sulfur compounds

of onions, garlic, leeks, and chives seem to boost

the immune system and inhibit tumors Many

plants including vegetables produce FLAVONOIDS, abroad family of substances that can function asantioxidants to block the oxidative damage to cellsdue to free radicals Free radical-induced damage isnow believed to be a factor in some degenerativediseases, like heart disease, associated with aging.For example, dark green leafy and orange vege-tables and some fruits are a rich source of

CAROTENOIDS, including beta-carotene These tochemicals function as antioxidants and theyenhance the immune system As a group theyreduce the risk of some forms of cancer

phy-Rather than a simple ingredient, vegetables vide a wide array of known phytochemicals;undoubtedly, many more remain to be discovered.Phytochemicals appear to be most effective whensupplied in combination with a range of substances

pro-as found in minimally processed foods, includingvegetables Their effects are often synergistic, that

is, the overall effect of a combination is more eficial than any one isolated ingredient

ben-Vegetable Processing

Although fresh vegetables are available year rounddue to large refrigerated warehouses and fast trans-portation systems, processed vegetables remain animportant part of the American diet A variety ofmethods are used to prepare or to preserve vegeta-bles Several of the more common methodsinclude:

Canning Developed in the 19th century inFrance, canning remains a major food preservationstrategy This process involves heating vegetables inmetal or glass containers to a sufficiently high tem-perature to destroy microorganisms that causespoilage or disease Heat-treated contents aresealed against air to prevent oxidation

Drying Drying food in the sun for preservationhas been carried out for thousands of years Dryingmust be carried out rapidly to avoid changes innutrients, flavor, or texture The action of plantenzymes that darken produce, destroy nutrientsand alter flavor can be limited by blanching (a briefheat treatment) or by treatment with preservativeslike sulfites or antioxidants such as VITAMIN C

Freezing Commercial techniques for rapidcooling and freezing allow many vegetables toretain most qualities of fresh vegetables for periods

vegetables 643

lasting up to eight to 12 months Blanching slows

alterations in flavor, color, and texture of frozen

vegetables

Pickling Vegetables can be preserved in a salt

solution (brine) or in VINEGAR, or a combination of

the two Pickled cucumber and relishes are common

food items Commercially pickled products require

heating to destroy microorganisms and to inactivate

plant enzymes that alter vegetables properties

Raw or Cooked Vegetables?

There are certain advantages to eating cooked

veg-etables Cooking a vegetable can increase the

avail-ability of beta-carotene because it is released from

storage sites in plant cells Cooking starchy

vegeta-bles breaks down starch granules so they can be

digested On the other hand there are advantages

to eating vegetables raw Raw vegetables may

con-tain higher levels of heat-sensitive nutrients

because cooking decreases the content of

water-soluble vitamins For example, baked potatoes and

sweet potatoes lose about 20 percent of the B

vita-mins and vitamin C Boiling causes lower losses

Boiling leaches B vitamins and minerals out of

veg-etables Losses may be as high as 80 percent

Steaming and microwave cooking of vegetables

greatly reduces this loss Boiling also removes

vita-mins and minerals Note that keeping foods warm

on a steam table increases the loss of vitamins such

as vitamin C, thiamin, and riboflavin

On the other hand, vegetables that have not

been stored properly, or have been handled

care-lessly, can suffer similar nutrient losses Slicing,

mashing, dicing, mincing, and grating break

veg-etable cells and expose vitamins to oxygen and

degradative enzymes Vitamin C is especially

sensi-tive to oxygen exposure The longer the storage

period for sliced vegetables, the greater the loss of

vitamin C (See also BALANCED DIET; DIETARY GUIDE

-LINES FOR AMERICANS; FOOD PRESERVATION; FOOD

PROCESSING; FOOD GUIDE PYRAMID; ORGANIC FOODS.)

Graziano, J M et al “A Prospective Study of

Consump-tion of Carotenoids in Fruits and Vegetables and

Decreased Cardiovascular Mortality in the Elderly,”

Annals of Epidemiology 5 (1995): 225–260.

vegetable shortening A form of saturated fat,

prepared from vegetable oil, that resembles animal

fat A major advantage of vegetable shortening isthat, unlike lard, butter, or beef fat, it does not con-tain CHOLESTEROL Vegetable shortening does con-tain the same high calories as butter or lard,however Vegetable shortening is a product of thechemical processing called hydrogenation Thisprocess adds hydrogen atoms to unsaturated FATTY ACIDS, thereby converting naturally liquid fat (oils)

to materials with varying degrees of stiffness ally several different fats are blended to achieve thedesired consistency of a shortening CORN OIL, COT-

Usu-TONSEED OIL, SOYBEAN oil, OLIVE OIL, PALM OIL,

PEANUT oil, SAFFLOWER oil, and SESAME oil may becombined Shortening, like other hydrogenatedvegetable oils, contains TRANS-FATTY ACIDSas a by-product of manufacture The long-term safety oftrans-fatty acids has been questioned A diet high

in saturated fat is linked to an increased risk of

HEART DISEASEand CANCER (See also HYDROGENATED VEGETABLE OIL; VEGETABLE OIL.)

vegetarian One who eats predominantly VEGETA

-BLES, FRUITS, GRAINS, and NUTSand either limits orexcludes animal products, including MEAT, FISH,

SEAFOOD, and dairy products from the diet With athoughtful selection of a variety of foods, vegetari-ans can easily meet all their nutrient needs Peoplechoose vegetarianism for a variety of reasons Vegetarianism may be related to religious or philo-sophical beliefs Ecologically, vegetarianism repre-sents a more efficient use of energy than relying onmeat and meat products From a health perspec-tive, plant products do not contain the growth pro-moters and antibiotics used in poultry and meatproduction nor do they contain cholesterol Plantsare excellent sources of FIBER and ESSENTIAL FATTY ACIDS

There are varying degrees of vegetarianism:

• Vegans rely on foods of plant origin and omit allmeat, poultry, fish, and eggs, as well as milk andmeat products

• Fruitarians rely on dry or raw fruits, togetherwith nuts, honey, grains, LEGUMES, and OLIVE OIL

while excluding animal products

• Semivegetarians occasionally eat some meat,fish, or poultry, eggs and milk or cheese whilerelying on cereals, grains, fruit, and vegetables

644 vegetable shortening

Most “heart healthy” diets are semivegetarian

diets There are a variety of such diets

• Ovo-vegetarians include eggs with foods of plant

origin in the diet

• Lactovegetarians include milk and milk

prod-ucts, together with foods of plant origin

• Lacto-ovo-vegetarians include both milk

prod-ucts and eggs with grains, fruits, and vegetables

Vegetarians who eat dairy products tend to have

higher blood cholesterol levels than those who

do not

• Pescovegetarians include fish and seafood,

together with foods derived from plants

Vegetarians may have a reduced risk of obesity,

type II (adult onset) diabetes, GALLSTONES, and

CORONARY ARTERY DISEASE There is evidence that

vegetarian diets reduce the risk of breast CANCER,

DIVERTICULOSIS, colonic cancer, hemorrhoids,

OSTEOPOROSIS, and dental caries

Nutrient Needs

Vegans who are pregnant or lactating, children of

vegans, and people who are ill run the greatest risk

for certain nutrient deficiencies because these

indi-viduals have high nutrient needs that may not be

readily met by eating a limited variety of plant

foods

Minerals The amounts of many TRACE MINER

-ALSare low in plant products, and the body’s

abil-ity to absorb them from plant sources is often low

Milk and milk products provides the most of the

calcium and meat provides the most iron and zinc

in the usual diet Vegans may have difficulties in

obtaining minerals such as:

• CALCIUM Major plant sources are: BROCCOLI,

KALE, COLLARDgreens, kelp, PARSLEY, prunes, SE

-SAMEseeds, fortified TOFU, and fortified soymilk

• ZINC Sources are: whole grains, BREWER’S YEAST,

LIMA BEANS, SOYBEANS, sunflower seeds, PEAS,

LENTILS, and wheat germ

• IRON This nutrient occurs in dried beans and

peas, dried fruit, fortified cereals, and bread

Iron uptake can be significantly increased by

eating iron-rich vegetable foods with vitamin

C-rich foods (citrus fruit, berries, dark green leafy

vegetables)

• COPPER Copper occurs in AVOCADOS, BARLEY,

BEANS, broccoli, BEETS, PECANS, RAISINS, and beans

soy-• MANGANESE This nutrient occurs in avocados,

NUTS, seeds, whole grains, legumes, dried peas,and dark green leafy vegetables

Energy The energy demands of infants andgrowing children are quite relative to their bodysize Fat is a calorie-dense food that is an importantpart of a child’s diet Often vegetarian foods offerhigh fiber but low energy (fat) content When thediet provides inadequate calories, a muscle protein

is degraded for energy, not a desirable situation in

a young, growing body

Protein Dietary protein must supply adequateessential AMINO ACIDS(the amino acids that cannot

be fabricated in amounts to meet the body’srequirements) Plant proteins may be less easilydigested depending on the meal preparation Theiramino acid compositions are usually not as wellbalanced as animal protein Consequently, vegetar-ian diets based on a single grain like corn can con-tribute to MALNUTRITION Plant proteins fromdifferent sources can complement each other, sothat the net amino acid intake of a mixture of plantprotein can adequately meet the daily requirementfor essential amino acids For example, combiningwhole grain foods with legumes is a traditionalpractice (rice and beans, corn and beans, wheatand lentils, for example)

Vitamin D The best sources of this vitamin arefatty fish, egg yolk, liver, and milk and milk prod-ucts—all of which are eliminated from a strictlyvegetarian diet Exposure to sunlight may meetindividual needs; however, supplementation may

be necessary for people living in northern regions

of the United States during the winter months, aswell as for institutionalized people

B Vitamins A number of cereal grain productsare enriched with RIBOFLAVIN, THIAMIN, and NIACIN.Legumes and whole grains can provide significantriboflavin VITAMIN B12deficiency is a major con-cern for strict vegetarians There is probably novery good plant source, other than nutritional

YEAST The amounts provided in sea vegetables, mented soy, and algae may be inadequate The bestsources are animal products such as meat; thus a

fer-vegetarian 645

strict vegetarian may need a supplement, fortified

soy milk, or fortified meat analog Once vitamin

B12 deficiency has occurred, the resulting nerve

degeneration may not be reversible

Strict vegetarian diets are not recommended for

infants or children Pregnant women should plan

their diet very carefully to maximize

nutrient-dense foods and:

1 emphasize unrefined, whole foods;

2 use protein-rich sources like legumes, seeds,

and nuts;

3 eat a variety of fruits, vegetables, legumes, and

whole grains to assure adequate protein

com-plementation;

4 eat fruit and vitamin C-rich foods with each

meal to enhance iron uptake;

5 consider supplemental sources of vitamin B12,

vitamin D, calcium, and trace minerals or

prop-erly fortified sources;

6 eat enough food to provide adequate protein

and energy

(See also CHOLESTEROL-LOWERING DRUGS; COM

-PLETE PROTEIN.)

Appleby, P N et al “The Oxford Vegetarian Study: An

Overview,” American Journal of Clinical Nutrition 70,

suppl (1999): 525S–531S.

Key, T J et al “Health Benefits of a Vegetarian Diet,”

Pro-ceedings of the Nutrition Society 58 (1999): 271–275.

very low-density lipoprotein (VLDL) A

lipid-protein particle that transports FAT from the LIVER

to other tissues via the bloodstream After a

carbo-hydrate meal, the liver absorbs glucose from the

blood and converts it to fat (TRIGLYCERIDES) The

liver packages fat to export it to other parts of the

body via the bloodstream in the form of VLDL In

composition, VLDL resembles chylomicrons, the

fat transport vesicles from the intestine VLDL

contains triglycerides, a low amount of CHOLES

-TEROL, and two types of protein designated B-100

and C-II

When VLDL reaches the capillaries, its

triglyc-erides are broken down by an enzyme in the walls

of the capillaries called lipoprotein lipase Tissues

then absorb the released fatty acids After releasing

their fat, VLDL remnants follow an unusual

path-way: They become enriched in cholesterol as theyare transformed in the blood to LOW-DENSITY LIPOPROTEIN(LDL)—the particle that carries choles-terol to tissues

The blood levels of both chylomicrons and VLDLincrease for several hours after eating Therefore,lab tests that measure triglycerides in serum, theclear cell-free fluid remaining after blood clots, areusually performed after an overnight fast whenlevels have stabilized Middle-aged white maleswith high levels of serum triglycerides (essentiallyVLDL) and high LDL appear to be more likely tohave heart attacks than men with normal levels,even in the people with somewhat elevated serumcholesterol levels The risk of heart attack maydecrease by lowering serum triglycerides and rais-ing HIGH-DENSITY LIPOPROTEIN(HDL), the “desirablecholesterol.” (See also CARDIOVASCULAR DISEASE; FAT METABOLISM.)

villi Microscopic, fuzzy layer coating the innerside of the wall of the SMALL INTESTINElike a shagcarpet Cells that line the surface of villi possessnumerous, tiny projections called MICROVILLI If all

of the intestinal folds, villi, and microvilli were tened out, the total surface area would be aboutthe size of a tennis court Thus villi dramaticallyincrease the absorptive area of the intestinal sur-face and facilitate efficient nutrient uptake CELIAC DISEASE, CROHN’S DISEASE, and intestinal parasiticdiseases (like GIARDIASIS) can lead to a loss of thevilli and subsequent MALABSORPTIONand maldiges-tion syndromes With appropriate treatment anddietary modification, the villi can grow back anddigestion can improve (See also DIGESTION; DIGES-

flat-TIVE TRACK.)

villikinin A hormone produced by the SMALL INTESTINE that stimulates the movement of VILLI,microscopic hair-like projections that coat theinner surface of the small intestine This actionserves to mix chewed food and digestive juice(CHYME) and to increase nutrient absorption by theintestine (See also DIGESTION; ENDOCRINE SYSTEM.)

vinegar A dilute solution of ACETIC ACID The

term is derived from the French vinaigre, which

646 very low-density lipoprotein

means sour wine Vinegar has been used in food

preservation and medicine for thousands of years

Typically vinegar contains 4 percent to 12 percent

acetic ACID, which is produced by the bacterial

oxidation of alcohol formed by the fermentation of

sugars and fruits Apples yield cider vinegar;

grapes, wine vinegar; and sugar and hydrolyzed

starches from corn and wheat, white vinegar

Depending upon the nature of the fruit fermented,

the resulting vinegar will have a unique flavor

without adding significant calories Vinegar

pro-vides only two calories per teaspoon Because it

is so acidic, vinegar is used to preserve foods in

pickling In salad dressing, MAYONNAISE, MUSTARD,

and tomato sauce, vinegar helps retard

spoil-age Vinegar contains traces of minerals but it is

not a significant food source (See also FOOD PRO

-CESSING.)

vitamin An essential organic nutrient Minute

amounts of vitamins participate in three general

functions of the body: growth, protection, and

energy regulation There are a total of 13 vitamins

Four are fat-soluble vitamins A, D, E, and K The

rest are water-soluble Eight vitamins are in the B

complex: RIBOFLAVIN (B1), THIAMIN (B2), NIACIN

(B3), VITAMIN B6, vitamin B12, FOLIC ACID, PAN

-TOTHENIC ACID, and biotin VITAMIN Cis also

water-soluble but is not considered a B vitamin, which

function as enzyme helpers (coenzymes)

Vitamins either cannot be synthesized by the

body or they cannot be made in adequate amounts,

so they must be supplied by the diet As examples

of the latter, vitamin D can be made in the skin

when exposed to sunlight, while some niacin can

be made from the amino acid tryptophan The

intestine is a source of BIOTIN, pantothenic acid, and

VITAMIN K; these are supplied by “friendly”

intesti-nal bacteria, though the exact amounts supplied

are difficult to assess

The term vitamin dates from 1912, and the first

vitamin to be isolated was vitamin A in 1913

Thi-amin was discovered in 1926, vitThi-amin K in 1929,

and vitamin C in 1932 Vitamin B12was the most

recent vitamin to be discovered (1948) Before a

compound can be classified as a vitamin, it must be

proven that animals must obtain the compound

from their diet Typically, scientists test lab animals

such as mice with a diet free of the test substance,together with a dose of antibiotics to eliminateintestinal bacteria

Vitamins originate chiefly from plant sources.Except for vitamin D and vitamin C, vitamins arepresent in animal tissue only if the animal con-sumes foods containing them or harbors microor-ganisms capable of synthesizing them B vitaminsare universally distributed; fat-soluble vitaminsmay be absent from some types of organisms Each

of the vitamins plays a specific role in the body; adeficiency of one vitamin cannot be eliminated byconsuming an excess of another

Fat-Soluble Vitamins

VITAMIN A, VITAMIN D, VITAMIN E, and vitamin K areoily materials and dissolve in fats and oils, not inwater Unlike the B complex, these vitamins gener-ally do not serve as enzyme helpers, nor are theyinvolved in energy production; each has anentirely different function, ranging from acting as

an ANTIOXIDANT(E), to producing a visual pigmentfor night vision (A), to blood clothing (K), and tobone formation (D)

Fat-soluble vitamins are absorbed best whenthey are eaten with fats and oils These vitaminsare stored in the body, so they do not need to beconsumed daily Because they are stored, excessiveconsumption can lead to high tissue levels resulting

in toxic side effects, especially for vitamins A and

D For example, 50,000 international units of min A over several months can cause toxic symp-toms in adults Symptoms of toxicity, such as achyjoints, fatigue, headaches, and nausea, disappearwhen the high intake stops What represents anexcessive intake depends on many factors, includ-ing the type of vitamin, individual tolerance, whichvaries with age, and the length of time for whichthe supplement is taken

vita-Water-Soluble Vitamins

B complex vitamins help convert food into energy;they include THIAMIN(B1), RIBOFLAVIN(B2), NIACIN

(B3), VITAMIN B6, pantothenic acid, and biotin

FOLIC ACIDand vitamin B12are involved in ing new cells, while vitamin C serves as an antiox-idant and helps build healthy capillaries, gums, andjoints Except for vitamin B12, water-soluble vita-mins are not stored well in the body and must be

build-vitamin 647

replenished daily Excesses are generally excreted

in the urine

Vitamin Deficiencies

Long-term vitamin deficiencies often lead to

seri-ous illness Deficiencies can be due to an

inade-quate diet (MALNUTRITION); inability to digest food

(maldigestion); inability to absorb vitamins due to

damage to the intestine or to competition with

another material such as a drug (MALABSORPTION);

increased physiological need as during pregnancy;

growth, injury, choice of lifestyle, or other

envi-ronmental factors

Physicians may use lab tests to diagnose vitamin

deficiencies Most tests involve blood analyses,

even though these are not always reliable For

example, a common antibody test for serum

vita-min B12 detects both vitamin B12 together with

inactive derivatives Measurement of enzyme

lev-els or levlev-els of metabolic products can provide

use-ful information Dietary analysis can reveal levels

of nutrients in the diet and guide a nutritional

eval-uation and assessment of individual needs

comple-menting the physical examination and health

history

Natural vs Synthetic Vitamins

Natural vitamins are those occurring in food All

substances classified as vitamins have been isolated

from animal or plant sources, and most have been

chemically synthesized in the lab to establish their

structures In other words, synthetic vitamins are

usually identical to the product in cells As an

exam-ple, vitamin C in cells is defined chemically as

L-ascorbic acid, identical to synthetic L-L-ascorbic acid

Most vitamins found in supplements are chemically

synthesized, because there simply is not enough of

most vitamins extracted from plant materials to

meet world demand Most vitamin C comes from a

few major commercial sources worldwide

A few synthetic vitamins differ from the natural

forms Synthetic vitamin E, called d,

1-alpha-tocopherol, is a mixture of both left- and

right-handed molecules, while the natural alpha

toco-pherol is a single form called d-tocotoco-pherol The

synthetic product is adjusted to provide the same

biological activity as the natural form Certain

vita-mins like vitamin B12 possess structures that are

too complex for a convenient lab synthesis

Micro-bial sources have been selected to produce largeamounts

Recent surveys show that about 158 millionconsumers take supplements and spend about $8.5billion yearly on vitamins, minerals, and other sup-plements One explanation for this widespreadpractice is that many people have subclinical defi-ciencies They are not sick, but they are not well,either They may want to feel more energetic and

to have more stable moods Others want to takesupplements as insurance in preventing certain dis-eases if they live in a polluted environment or iftheir genetic makeup, medical history, and lifestylechoices warrant it A growing number of con-sumers want to promote optimal health Althoughthere is a natural tendency to search for an easysolution to health problems, there are limitsregarding what vitamins can do for health No sin-gle supplement can compensate for overindul-gence, physical inactivity, or genetic predisposition.Deciding who needs vitamin supplements andhow much should be taken is a controversial area.Conventional wisdom says that by following

DIETARY GUIDELINES FOR AMERICANSand using a ommended plan such as the FOOD PYRAMID, an indi-vidual should be assured of an adequate supply ofnutrients Thus, if an individual is healthy and iseating a BALANCED DIET, vitamin supplementswould not be needed There is general agreementthat individuals with well recognized needs mayrequire supplements These people include:

rec-• women with heavy menstrual bleeding (extra

IRON)

648 vitamin

• women taking oral contraceptives (may need

extra vitamin B6)

• pregnant women (extra iron, folic acid, and CAL

-CIUM)

• malnourished individuals, including dieters,

elderly people with a low caloric intake, chronic

alcoholics, and those with other chemical

dependencies

• strict vegetarians (many need extra iron, zinc,

calcium, and vitamin B12)

• newborn infants (may be deficient in vitamin E

and vitamin K)

• individuals with chronic disorders, such as

patients with OSTEOPOROSIS (may need extra

vitamin D, calcium, magnesium, and trace

minerals)

• hospitalized patients Patients in hospitals and

institutionalized people may become deficient in

one or more vitamin

• people who smoke (extra vitamin C)

Another viewpoint is that many people who live

in modern industrial societies and are exposed to

environmental stressors and rely on refined foods,

often can benefit from supplements for optimal

health and maximal longevity However, the

opti-mal amounts for any vitamin are merely estimates

Other individuals may benefit from supplements

when their nutrient consumption is below normal

although they lack symptoms of serious deficiency

diseases It has been proposed that nutrient needs

increase with:

• exposure to pollution

• physical and mental stress

• frequent skipping of meals

• increased reliance on highly processed foods

• inadequate exercise and rest

• use of recreational drugs and alcohol

• widespread chemical and food sensitivities

• increased prevalence of conditions characterized

by suppressed immunity, including AIDS

• dieting

There are many advantages in obtaining

nutri-ents from food: It is practically impossible to get an

overdose Food supplies mixtures of nutrients and

mixtures are what the body needs; food supplies

other substances that may have beneficial effectsand are not found in a pill or capsule But supple-ments can be used as part of a wellness program toprevent illness and promote well-being Such aprogram should include physical exercise, eatingwholesome meals, maintaining psychological fit-ness and emotional stability

Any patient who is considering taking dietarysupplements should:

• Consult with a knowledgeable health sional about possible contraindications, adverseside effects, or interference with other medica-tions or treatments the patient is receiving

profes-• Avoid taking any supplements while pregnant

or nursing unless under the advice or sion of a doctor

supervi-• Focus on individual needs—more does not essarily mean better

nec-• Tell their doctors what supplements they aretaking, especially before submitting to a blood orurine test, as the results can be affected by somesupplements

• Be aware of sensitivities to wheat, soy, yeast,corn, milk, artificial coloring, starch, or preserv-atives—many supplements contain these prod-ucts

• Select supplements with multiple nutrients—many nutrients work best in tandem with others

• Test supplements for their ability to dissolve (asign that they will be effective) by placing them

in a cup of warm water with a teaspoon of gar to see if they disintegrate within 45 minutes

vine-• Keep vitamins and minerals out of children’sreach

• Monitor the effect of the supplement to ensure

it is providing a health benefit

(See also ORTHOMOLECULAR MEDICINE; SUBCLINI

-CAL NUTRIENT DEFICIENCY.)Hathcock, J N “Vitamins and Minerals: Efficacy and

Safety,” American Journal of Clinical Nutrition 66, no 2