The Encyclopedia Of Nutrition And Good Health - R pdf

Oxygen binding is reversible so 552 Recommended Nutrient Intakes COUNCIL FOR RESPONSIBLE NUTRITION Minerals: Historical Comparison or RDIs, RDAs, and DRIs, 1968 to Present NUTRIENT RDI*

549

radiation preservation of food See FOOD IRRADI

-ATION

radiation therapy (radiotherapy) Using carefully

aimed doses of radiation to shrink or destroy

cer-tain types of CANCER, especially tumors that cannot

be removed safely with surgery During treatments

highly calibrated equipment bombards cancerous

tumors with high doses of radiation without

expos-ing neighborexpos-ing healthy tissue Typically a patient

undergoes daily treatments for two to nine weeks

As with other cancer treatments such as

che-motherapy, radiation therapy can cause negative

and sometimes dangerous nutrition-related side

effects, including nausea, vomiting, mouth sores,

appetite loss, heartburn, difficulty swallowing,

bloating, and diarrhea Inadequate nutrition during

radiation therapy can slow healing and recovery

During this time most patients need to make

sure they eat enough and that they get the right

balance of nutrients to keep up their strength,

decrease the risk of infection, and promote healing

Some helpful tips include eating a small meal about

an hour before each treatment; eating small,

fre-quent meals throughout the day; and

supplement-ing meals with liquid meal replacements to

increase caloric and protein intake Patients should

consider seeking the support of a nutritionist to

ensure they are getting the right amount and

com-bination of nutrients during radiation therapy

Chase, Daniella et al What to Eat When You Have Cancer.

New York: Contemporary Books, 1996.

radioactivity See CARCINOGEN

radish (Raphanus sativus) A root vegetable with

a distinctive sharp flavor; related to broccoli, kale,

and cabbage These cruciferous vegetables possess anticancer properties The radish probably origi-nated in western Asia and was used by Babylonians and ancient Egyptians It was introduced to China around 500 B.C., where new varieties were devel-oped with a tangy flavor According to the variety, radishes may be round, tapered, or oblong, and the color can be white, red, yellow, purple, or black The Oriental radish, daikon, can weigh up to 5 lb (2.3 kg) The common radish (red globe) is usually eaten raw as a condiment and as a salad vegetable Black radishes are the size of turnips; their flesh is white and very pungent Radishes can be cooked as

a vegetable, added to soups, or pickled The nutri-ent contnutri-ents of 10 radishes (raw, 45 g) is 7 calories; protein, 0.27 g; carbohydrate, 1.6 g; fiber, 0.24 g; vitamin C, 10 mg; riboflavin, 0.02 mg; niacin, 0.135 mg

radon See CARCINOGEN

raisin A dried form of several varieties of grapes Half of the world’s supply of raisins comes from the San Joaquin Valley of California Muscat, Sultana, Thompson Seedless, and Zante Currant represent the principal varieties of grapes suitable for raisins Ripe grapes are dehydrated either mechanically or are sun-dried so that raisins contain 17 percent water, compared to about 80 percent for grapes Nutrients like sugar are much more concentrated

in raisins than in the fresh fruit, and raisins are a good source of iron, potassium, B vitamins, dietary fiber, and carbohydrate (calories) Golden raisins are dried Thompson Seedless grapes that have been treated with sulfur dioxide then dehydrated in forced dry air Other varieties include currants (from Black Corinth grapes); Sultanas (from a large green grape), popular in Europe; Muscat raisins

(from green Muscat grapes), which are fruity

fla-vored and often used in fruit cakes Unopened

packages of raisins can be stored a year when

refrigerated, longer when frozen The nutrient

con-tent of 1 cup (seedless, 145 g) is: 435 calories;

pro-tein, 4.7 g; carbohydrate, 115 g; fiber, 9.6 g; fat, 0.7

g; iron, 3.0 mg; potassium, 1,089 mg; vitamin C, 5

mg; thiamin, 0.23 mg; riboflavin, 0.13 mg; niacin,

1.29 mg

become oxidized through exposure to air Rancid

fat has an “off” flavor and a disagreeable odor In

meat, iron-containing protein react with oxygen to

produce free radicals that cause loss of flavor

accompanying fat decomposition The oxidation of

fats usually occurs spontaneously, though slowly,

at room temperature Exposure to heat, light, and

trace metals like IRONgreatly speeds the reaction of

oxygen Rancidity lowers the content of other

lipids, including VITAMIN Aand VITAMIN E Thus, the

rancid foods are less wholesome and less nutritious

than fresh foods

At a molecular level, oxygen and a reactive

chemical species called FREE RADICALS, molecules

that are electron deficient, can attack unsaturated

FATTY ACIDSin fats and oils Unsaturated fatty acids

contain double bonds that lack pairs of hydrogen

atoms These bonds are fragile and susceptible to

chemical modification, leading to the formation of

PEROXIDES, which are potent intermediates in fat

oxidation Lipid peroxides can trigger INFLAMMA

-TIONand spontaneously decompose into more free

radicals plus fragments that are both cytoxic (cell

killing) and mutagenic (causing mutations)

Most cells contain an antioxidant enzyme

sys-tem called GLUTATHIONE PEROXIDASE that converts

unstable oxidized lipids (lipid peroxides) to

harm-less fatty acids that can be used for energy

A growing family of FOOD ADDITIVES called

ANTIOXIDANTS is used to control or prevent

oxida-tion of processed vegetable oils and processed foods

containing fats and oils in order to increase their

stability during storage Ascorbic acid (VITAMIN C)

and vitamin E prevent oxidative damage, and

addi-tives like CITRIC ACIDcan bind metal ions that could

otherwise catalyze a reaction with oxygen

Syn-thetic antioxidants, including BHA, BHT, and

PROPYL GALLATE, are designed to disarm free radicals before they can cause damage Because of the safety concerns raised about synthetic antioxidants, the food industry has studied naturally occurring antioxidants that can be added to foods and fats and oils to stabilize them As an example, rosemary extracts have proven effective in stabilizing veg-etable oils (See also FOOD PRESERVATION.)

rapeseed (Brassica napus; B campestris) One of the five most important oil-producing seed crops and the only oil seed successfully grown world-wide The origins of rapeseed are obscure, although reference to it is made in 3,000-year-old Sanskrit writings The seed contains 40 percent to 50 per-cent oil Rapeseed oil typically contains erucic acid,

a fatty acid analog that interferes with FAT METABO -LISM in experimental animals when consumed in large amounts New strains of rapeseed that con-tain little of this acid or another antinutrient, glu-cosinolate, were developed in Canada and Europe The oil derived from the new strains of rapeseed, CANOLA OIL, contains significantly more OLEIC ACID, the monounsaturate of OLIVE OIL The fatty acid composition of canola oil resembles olive oil and it too is classified as a monounsaturate Canola oil is used in SHORTENING, MARGARINE, salad oil, MAYON -NAISE, and as a cooking oil It contains 6.9 percent saturated fatty acids; 34.6 percent polyunsaturated fatty acids; and 58.5 percent monounsaturated fatty acids (See also VEGETABLE OIL.)

raspberry (Rubus spp.) The FRUIT of a family of brambles (Rosaceae) that includes BLACKBERRYand loganberry Raspberries resemble blackberries, except the berry core remains on the vine when raspberries are picked Each fruit is composed of tiny drupes, each of which can be considered a fruit Raspberries apparently originated in eastern Asia They now grow wild from the Arctic Circle to northern South America Cultivation was probably initiated in Europe in the 16th century Red rasp-berries are the most common variety in America, but they may be yellow, black, or purple as well Oregon and Washington are major raspberry pro-ducers Ninety percent of the U.S crop is processed, and most is quick frozen because it has a short shelf life Most red or dark blue-purple berries contain

550 rancidity

pigments (ANTHOCYANINS) that have beneficial

effects on connective tissue and inflammation

These and related berries contain ellagic acid, a

substance that may help prevent some forms of

cancer Raspberries are good sources of FIBER,

POTASSIUM, and VITAMIN C The nutrient contents of

1 cup (raw, 123 g) are: 60 calories; protein, 1.1 g;

carbohydrate, 14.2 g; fiber, 9.1 g; fat, 0.7 g;

potas-sium, 187 mg; vitamin C, 31 mg; thiamin, 0.04 mg;

riboflavin, 0.11 mg; niacin, 1.11 mg (See also

FLAVONOIDS.)

raw fish See SEAFOOD

raw meat disease See TOXOPLASMOSIS

raw milk See MILK

raw shellfish See SHELLFISH

raw sugar See SUCROSE

RD See DIETITIAN

RDA See USRDA

recommended daily allowances See USRDA

Food and Nutrition Board of the U.S National

Academy of Sciences has periodically published

recommended average daily intakes for several

nutrients selected as adequate to meet the dietary

needs of most healthy Americans Generally, the

RDAs were reviewed every five years or so, the

most recent edition being 1989 RDAs were

estab-lished for the following categories:

• ENERGY;

• fat-soluble VITAMINS: VITAMINS A, VITAMIN D, VIT

-AMIN E, VITAMIN K(added in 1989);

• water-soluble VITAMINS: VITAMIN C, FOLIC ACID,

NIACIN, RIBOFLAVIN, THIAMIN, VITAMIN B6, VITAMIN

B12;

• macrominerals: CALCIUM, MAGNESIUM, PHOS

-PHORUS;

• trace minerals: IODINE, IRON, ZINC, MAGNESIUM, SELENIUM(added in 1989)

The RDAs have been replaced by a new set of dietary recommendations called DIETARY REFERENCE INTAKES(DRI) These are meant to shift nutritional focus from deficiency to lowering the risk of dis-ease They reflect the latest research on what levels

of nutrition are best to combat diseases such as can-cer, osteoporosis, and CORONARY ARTERY DISEASE The DRIs incorporate the RDAs along with three other nutrient-based reference values: the mated average requirement (the daily intake esti-mated to meet the nutrient requirements of people

in a specific age or gender group); the adequate intake (when an estimated average requirement is not available, this intake level is determined based

on observing what amount of nutrients sustain health in a specific group of people); and the toler-able upper intake level (the daily nutrient intake that is unlikely to pose risks of adverse health effects to almost all healthy people of a specific age

or gender)

The RDAs are based on population needs Groups referred to in the RDA tables include: infants; chil-dren between the ages of one and three; between four and six; and between seven and ten; males or females between the ages of 11 and 14; between 15 and 18, 19 and 22, 23 and 50; men and women over 50; pregnant women; and lactating women All recommendations except for energy intend that nutrient intake will exceed the requirements

of most healthy people This decision was made in order to address the problem of variability in indi-vidual nutrient needs Mathematically, RDAs have been chosen to cover 97.5 percent of a given group

of people by selecting values lying between two standard deviations above the mean nutrient requirement for a population

The determination of the RDAs for energy dif-fers significantly from other recommendations for specific nutrients The allowances for energy employ the average (mean) requirement for each population reported The mean was chosen be-cause a higher recommended energy allowance would significantly increase the odds that many people, who have average energy needs, would become overweight

Recommended Dietary Allowances 551

The RDAs were selected after evaluating

evi-dence that comes from animal as well as human

studies Nutrient requirements are generally set

at levels that ensure that body stores are adequate

for normal functions, growth, and development In

people, the nutrient turnover and rates of

deple-tion of nutrient body pools are most usually

un-known Therefore experimental evidence for

setting the RDAs generally relies on the following:

intakes that maintain adequate blood levels;

excre-tion of surplus doses in urine or feces; maintenance

of a balance of intake and body losses;

measure-ment of body function or metabolic process;

knowledge of the amount of a nutrient needed to

prevent or even cure disease in humans and

some-times in experimental animals; and examination of

nutrient intakes of apparently healthy people (See

also FOOD GUIDE PYRAMID.)

King, J “The Need to Consider Functional Endpoints in

Defining Nutrient Requirements,” American Journal of

Clinical Nutrition 63 (1996): 983S–984S.

Recommended Nutrient Intakes (for Canadians)

(RNI) The Canadian version of the U.S

Recom-mended Dietary Allowances The RNIs are being replaced by the DIETARY REFERENCE INTAKES, estab-lished by Canadian and U.S scientists according to

a review process overseen by the Food and Nutri-tion Board of the U.S NaNutri-tional Academy of Sci-ences

red blood cells (erythrocytes) The major type of cells in blood Red blood cells transport OXYGENto all cells of the body, and their color reflects the high content of HEMOGLOBIN, the red oxygen transport protein The importance of red blood cells is indi-cated by their numbers: The average person has 35 trillion red blood cells Males have about 5 million red blood cells per milliliter of blood and females have about 4.5 million per milliliter Each red blood cell contains about 280 million hemoglobin (pro-tein) molecules The blood of the average adult male contains 14 to 16.5 g of hemoglobin per 100

ml of blood; the average adult female has 12 to 14

g per 100 ml

Inhalation brings fresh air into the lungs where hemoglobin binds oxygen, which is then carried to tissues via arteries Oxygen binding is reversible so

552 Recommended Nutrient Intakes

COUNCIL FOR RESPONSIBLE NUTRITION Minerals: Historical Comparison or RDIs, RDAs, and DRIs, 1968 to Present NUTRIENT RDI* 1968 RDA** 1974 RDA** 1980 RDA** 1989 RDA** DRIs***

(700 adult)

* The Reference Daily Intake (RDI) is the value established by the Food and Drug Administration (FDA) for use in nutrition labeling It was based initially on the highest 1968 Recommended Dietary Allowance (RDA) for each nutrient, to assure that needs were met for all age groups.

** The RDAs were established and periodically revised by the Food and Nutrition Board Value shown is the highest RDA for each nutrient, in the year indicated for each revision.

*** The Dietary Reference Intakes (DRI) are the most recent set of dietary recommendations established by the Food and Nutrition Board of the Institute of Medicine, 1997–2001 They replace previous RDAs, and may be the basis for eventually updating the RDIs The value shown here is the highest DRI for each nutrient.

Council for Responsible Nutrition, 2001

1875 I Street N.W Suite 400, Washington, D.C 20006 • (202) 872-1488

red blood cells 553

COUNCIL FOR RESPONSIBLE NUTRITION Minerals: Comparison of Current RDIs, New DRIs, and ULs

* The Reference Daily Intake (RDI) is the value established by the Food and Drug Administration (FDA) for use in nutrition labeling It was based initially on the highest 1968 Recommended Dietary Allowance (RDA) for each nutrient, to assure that needs were met for all age groups.

** The Dietary Reference Intakes (DRI) are the most recent set of dietary recommendations established by the Food and Nutrition Board of the Institute of Medicine, 1997–2001 They replace previous RDAs, and may be the basis for eventually updating the RDIs The value shown here is the highest DRI for each nutrient.

*** The Upper Limit (UL) is the upper level of intake considered to be safe for use by adults, incorporating a safety factor In some cases, lower

ULs have been established for children.

# Upper limit for magnesium applies only to intakes from dietary supplements or pharmaceutical products, not including intakes from food and water.

ND Upper Limit not determined No adverse effects observed from high intakes of the nutrient.

Council for Responsible Nutrition, 2001

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COUNCIL FOR RESPONSIBLE NUTRITION Vitamins: Historical Comparison of RDIs, RDAs, and DRIs, 1968 to Present NUTRIENT RDI* 1968 RDA** 1974 RDA** 1980 RDA** 1989 RDA** DRIs***

Vitamin E 30 IU (20 mg) 30 IU (20 mg) 15 IU (10 mg) 10 mg (15 IU) 10 mg (15 IU) 15 mg #

synthetic ##

Biotin (300 mcg) 150–300 mcg 100–300 mcg 100–200 mcg 30–100 mcg 30 mcg

* The Reference Daily Intake (RDI) is the value established by the Food and Drug Administration (FDA) for use in nutrition labeling It was based initially on the highest 1968 Recommended Dietary Allowance (RDA) for each nutrient, to assure that needs were met for all age groups.

** The RDAs were established and periodically revised by the Food and Nutrition Board Value shown is the highest RDA for each nutrient, in the year indicated for each revision.

*** The Dietary Reference Intakes (DRI) are the most recent set of dietary recommendations established by the Food and Nutrition Board of the Institute of Medicine, 1997–2001 They replace previous RDAs, and may be the basis for eventually updating the RDIs The value shown here is the highest DRI for each nutrient.

(continues)

that hemoglobin releases oxygen in tissues where

there is a low concentration of oxygen Elevated

CARBON DIOXIDEconcentration and acid production

from actively metabolizing tissues also promote

oxygen release from red blood cells Released

oxy-gen diffuses into cells where it oxidizes fuels to

car-bon dioxide Red blood cells pick up carcar-bon dioxide

for the return trip to the lungs via blood vessels

Red blood cells transport about 23 percent of

car-bon dioxide in this manner In the lungs red blood

cells release carbon dioxide and again bind incom-ing oxygen

Red blood cells are highly specialized The disk shape presents a larger surface area than a sphere, which helps the diffusion of oxygen into the cells Red blood cells lack a nucleus and MITOCHONDRIA and therefore cannot divide, nor use oxygen to derive energy from the oxidation of fuel molecules Instead they rely on GLYCOLYSIS, an oxygen-inde-pendent mechanism for oxidation of glucose

554 red blood cells

# Historical vitamin E conversion factors were amended in the DRI report, so that 15 mg is defined as the equivalent of 22 IU of natural vitamin E

or 33 IU of synthetic vitamin E.

## It is recommended that women of childbearing age obtain 400 mcg of synthetic folic acid from fortified breakfast cereals or dietary supple-ments, in addition to dietary folate.

### It is recommended that people over 50 meet the B 12 recommendation through fortified foods or supplements, to improve bioavailability Council for Responsible Nutrition, 2001

1875 I Street N.W Suite 400, Washington, D.C 20006 • (202) 872-1488

COUNCIL FOR RESPONSIBLE NUTRITION Vitamins: Comparison of Current RDIs, New DRIs, and ULs

200 mcg synthetic ##

* The Reference Daily Intake (RDI) is the value established by the Food and Drug Administration (FDA) for use in nutrition labeling It was based initially on the highest 1968 Recommended Dietary Allowance (RDA) for each nutrient, to assure that needs were met for all age groups.

** The Dietary Reference Intakes (DRI) are the most recent set of dietary recommendations established by the Food and Nutrition Board of the Institute of Medicine, 1997–2001 They replace previous RDAs, and may be the basis for eventually updating the RDIs The value shown here is the highest DRI for each nutrient.

*** The Upper Limit (UL) is the upper level of intake considered to be safe for use by adults, incorporating a safety factor In some cases, lower

ULs have been established for children.

# Historical vitamin E conversion factors were amended in the DRI report, so that 15 mg is defined as the equivalent of 22 IU of natural vitamin E

or 33 IU of synthetic vitamin E.

## It is recommended that women of childbearing age obtain 400 mcg of synthetic folic acid from fortified breakfast cereals or dietary supple-ments, in addition to dietary folate.

### It is recommended that people over 50 meet the B 12 recommendation through fortified foods or supplements, to improve bioavailability.

ND Upper Limit not determined No adverse effects observed from high intakes of the nutrient.

Council for Responsible Nutrition, 2001

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COUNCIL FOR RESPONSIBLE NUTRITION (continued)

(BLOOD SUGAR) to LACTIC ACID The surface of the

red blood cell possesses certain carbohydrate

clus-ters (blood group substances) that are the basis for

blood typing; for example, according to the ABO

blood groups and Rh blood groups

Formation

ERYTHROPOIESIS refers to the process of red blood

cell formation During embryonic development,

red blood cells are produced by the yolk sac, liver,

spleen, thymus gland, lymph nodes, and bone

marrow, while in adults, red blood cells come

from the bone marrow of long bones like the

femur, and from the cranium, sternum, ribs,

ver-tebrae, pelvis, and lymphoid tissues The initial

parent cells are called hemocytoblasts These cells

differentiate into proerythroblasts, an

intermedi-ate stage that eventually differentiintermedi-ates into

reticu-locytes (immature red blood cells), and finally into

mature red blood cells (erythrocytes) The usual

fraction of reticulocytes in blood is between 0.5

percent and 1.5 percent The percentage increases

with ANEMIA, when the number of functional red

blood cells becomes inadequate; with bleeding;

hemolysis (rapid breakdown of red blood cells);

and in response to supplementation for IRON

deficiency

The kidney stimulates the production of the

hormone, erythropoietin, which stimulates the

production of red blood cells in response to

low-ered oxygen pressure, as experienced at high

ele-vations When the body suddenly needs more red

blood cells, the kidneys become oxygen-deficient

and release an enzyme that converts a blood

pro-tein to erythropoietin

The levels of red blood cells represent a balance

between the formation and destruction of red

blood cells Aged red blood cells are destroyed by

the spleen and by the liver The protein portion of

hemoglobin is degraded to AMINO ACIDS; the red

pigment, HEME, is degraded to BILE PIGMENT,

biliru-bin, which is excreted, and releases iron, which is

reused

A number of nutrients besides iron support cell

division and protein synthesis in general, and red

blood cell formation in particular: FOLIC ACID, PYRI

-DOXINE, VITAMIN B12, and amino acids ANTIOXI

-DANTSlike VITAMIN Ehelp maintain the red blood

cell membrane and prevent fragility Deficiencies

of any of these nutrients can cause anemia, a con-dition resulting from an inadequate level of func-tional red blood cells Several inborn errors of metabolism (mutations) cause abnormal hemo-globins to be formed These in turn can alter the shape of red blood cells and shorten their life span, resulting in anemia Sickle-cell anemia and glucose 6 phosphate dehydrogenase deficiency are the most common (See also HEMATOCRIT; LEU -KOCYTES.)

COLORS

red meat See MEAT

red tide Refers to a plankton bloom often occur-ring in marine waters duoccur-ring the late summer and

fall The term red tide comes from the red-brown

color of plankton The plankton produce a nerve poison that can accumulate to dangerous levels in shellfish such as CLAMS and mussels although it does not affect the shellfish Eating contaminated clams, mussels, and oysters causes paralytic shell-fish poisoning The adage of avoiding shellshell-fish dur-ing months that end in the letter “r”—September, October, November, and December—is no longer appropriate because red tide alerts now occur in other months Red tide warnings by county health departments can be issued as early as April

Symptoms of paralytic shellfish poisoning in-cludes stomach cramps, dizziness, difficulty in breathing, and tingling mouth Symptoms can appear up to two hours after eating contaminated shellfish; in severe cases, poisoning can be fatal There is no antidote Immediate medical attention

is mandated (See also SEAFOOD.)

term for “USRDA” (Recommended Daily Allow-ance), a set of reference values introduced in 1973

to be used for vitamins, minerals, and protein to help consumers evaluate the nutritional content for food labels For the time being, RDIs are identi-cal to the USRDAs except for protein, which is adjusted to the specific needs of different age groups

Reference Daily Intake 555

NUTRIENT AMOUNT

Vitamin A 5,000 International Units (IU)

Vitamin C 60 milligrams (mg)

Vitamin B12 6 micrograms (mcg)

Pantothenic acid 10 mg

(Based on National Academy of Sciences’ 1968 Recommended

Diet-ary Allowances.)

Additions Jan 1, 1997

reference protein A source of PROTEINused as a

basis for comparing food proteins according to their

amino acid compositions Reference proteins

pro-vide all essential amino acids in sufficient quantity

to meet the needs of infants and children, who

require substantially more protein than adults,

based on their body weight, to support their higher

growth rates Another property of reference

pro-teins is that they are highly digestible High-quality

protein sources often used as reference proteins

include egg, human milk, meat, and fish The

amino acid patterns for human milk and whole egg

protein are as follows:

Amino Acid Human Milk Whole Egg

mg/100 g mg/100g

Methionine and

Phenylalanine and

The CHEMICAL SCORE attempts to measure the nutritive value of food protein in comparison with

a reference protein In this case, the amount of the least abundant limiting essential amino acid in the test protein is expressed as a percentage of that amino acid in the reference protein Thus, a good-quality protein source could have a chemical score

of 70 or above Most meat and dairy protein fall into this category (See also BIOLOGICAL VALUE; PRO -TEIN COMPLEMENTATION; PROTEIN EFFICIENCY RATIO.)

refined carbohydrates Highly purified SUGARSor STARCHES These substances occur in sweeteners and in products that are mainly starch Each type of refined carbohydrate supplies the same four calo-ries per gram Purified simple sugars and starches represent EMPTY CALORIES, that is, calories lacking

in VITAMINS, FIBER, PROTEIN, and MINERALS One of the most common refined carbohydrates

is table sugar (SUCROSE), highly purified from sugar beets or sugar cane by repeated crystallization The following sweeteners are only slightly less purified forms of sucrose: brown sugar, caramelized sugar, HONEY, MOLASSES, and turbinado sugar

Other refined sugars besides sucrose serve as common FOOD ADDITIVES:

• Dextrose (grape sugar) is another name for the pure compound of GLUCOSE, used by food man-ufacturers Dextrose occurs in corn syrup

• Maltodextrins are starch fragments containing several glucose units They yield glucose when digested and provide no other nutrients

• Fructose (fruit sugar) occurs as high FRUCTOSE CORN SYRUP This sweetener also contains glu-cose, but no other nutrient

• Sugar alcohols function as sweeteners: MANNI -TOL, SORBITOL, and XYLITOL None provides any-thing other than calories to overall nutrition

Refined Starches

Purified starches are isolated from WHEAT, CORN, and POTATOES, among other sources Starch is used

556 reference protein

as a thickener in many foods White flour is a

sta-ple of the American diet Though not pure starch,

white flour and products prepared from white

bread—cold BREAKFAST CEREALS, muffins, PASTRY,

pancake mix, pasta (spaghetti, noodles), and the

like—contain much less of the vitamins, minerals,

essential oils, and fiber than are found in the whole

grain from which they were derived Milling wheat

separates the starchy endosperm from the highly

nutritious germ and bran (the hull of the seed or

kernel)

Recent dietary guidelines have consistently

emphasized minimally processed foods like FRUIT

and VEGETABLES U.S DIETARY GUIDELINES FOR AMER

-ICANS (2000) recommend eating sweets sparingly

and suggest that whole grains, vegetables, and

fruits are the foundation of a healthy diet The

1992 FOOD GUIDE PYRAMID of the USDA

recom-mends three to five servings of vegetables, two to

four servings of fruit and six to 11 servings of rice,

bread, cereal, and pasta daily, with the admonition

to use sweets and added sugar sparingly (See also

CARBOHYDRATE METABOLISM; NATURAL SWEETENERS.)

ling-zhi) A fungus native to East Asia, where it has

been used since ancient times to treat a variety of

ailments and diseases, including ulcers, cancer, and

insomnia Its Chinese name, ling-zhi, means “herb

of spiritual potency.”

The fungus grows on rotting logs and stumps

The fruiting part of the fungus is a mushroom,

which has been harvested by Chinese herbalists for

at least 4,000 years The mushroom’s flesh can be

eaten whole, but because it is hard and bitter it is

more often cut up or dried for use in teas

Few reliable studies have been done to support

reishi’s medicinal uses However, researchers at a

Chinese university discovered that the fungus

con-tains a high level of polysaccharides, which are

known to stimulate the body’s immune system

Safety data are inadequate for pregnant and

breast-feeding women

helps increase blood pressure In response to a drop

in BLOOD PRESSURE, renin activates the HORMONE,

ANGIOTENSIN, which in turn stimulates the ADRENAL

GLANDSto produce ALDOSTERONE, the hormone that directs the kidneys to retain SODIUMand water Ele-vated levels of renin correlate with increased risk of heart attack among people with moderate high blood pressure (HYPERTENSION) Possibly too much angiotensin can trigger reduced blood flow to the heart (See also CARDIOVASCULAR DISEASE; PROTEASE.)

rumi-nants, such as calves, that contains the enzyme rennin Cheese production relies on the action of rennin that coagulate the proteins in milk, forming solid curds (from which cheese is made) and liquid whey (See also DENATURED PROTEIN.)

respiration, cellular The use of oxygen by cells to burn fuel nutrients for energy OXYGENdelivered by the blood is taken up by MITOCHONDRIA, particles in the cytoplasm that function as the cell’s power-houses Mitochondrial enzymes completely oxidize FAT, CARBOHYDRATE, and AMINO ACIDS to CARBON DIOXIDE and chemical energy released by this process is trapped as ATP ATP is the energy cur-rency of cells; it provides the necessary energy for the synthesis of cellular components—proteins, RNA, DNA—as well as for transmission of nerve impulses, muscle contraction and the transport of nutrients across cell membranes Carbon dioxide diffuses out of cells into the bloodstream, which transports it to the lungs to be expired Respiration requires specialized enzyme machinery called the terminal ELECTRON TRANSPORT CHAIN This sequence

of linked oxidation-reduction enzymes receives electrons from individual oxidation reactions of the cell and passes them on to oxygen, which is con-verted to water The sequential transfer of electrons

to oxygen is coupled with the generation of ATP, a process called OXIDATIVE PHOSPHORYLATION

Certain toxins and poisons like cyanide inhibit cellular respiration, limit ATP production and may ultimately cause death Nutrients required to support respiration include B vitamins NIACIN, RIBO -FLAVIN, THIAMIN, PANTOTHENIC ACID, and trace miner-als like COPPERand IRON Another nutrient that may

be required in the diet under certain conditions is COENZYME Q This lipid helps funnel electrons into the system (See also CARBOHYDRATE METABOLISM; FAT METABOLISM; RESPIRATORY QUOTIENT.)

respiration, cellular 557

respiratory chain See ELECTRON TRANSPORT

CHAIN

respiratory quotient (RQ) The ratio of the

vol-ume of expired CARBON DIOXIDEto the volume of

OXYGENconsumed This measurement can be used

to determine whether PROTEIN, CARBOHYDRATE, and

FATrepresent the major energy sources of the body

Carbohydrate and protein are more oxidized

(contain more oxygen), and less oxygen is required

to oxidize them completely to carbon dioxide

Therefore, their RQ values are higher than that of

fat: carbohydrate, 1.0; protein, 0.80; fat, 0.71;

mixed diet, 0.82 The RQ may exceed 1.0 if large

amounts of carbohydrate are being converted to

fat (See also METABOLISM.)

resveratrol A substance found in the skin of red

GRAPEs frequently used to make red WINEand grape

juice Resveratrol is a chemical that acts as an

antibiotic in the plants that produce it Although it

is found in the components of other plants,

includ-ing peanuts and eucalyptus, it appears in red grape

skin in high concentrations

Resveratrol is responsible in part for the CHOLES

-TEROL-lowering effect of red wine as determined by

animal studies It has also been suggested as the

possible explanation for the “French Paradox,” the

low incidence of heart disease among French

citi-zens who regularly eat high-fat foods and drink red

wine Additional research on humans is needed to

determine whether supplementation with

resvera-trol would benefit patients at risk of

cholesterol-related heart disease, and to establish the safety of

this supplement Several studies have confirmed

that resveratrol is an effective and powerful

ANTIOXIDANT Consequently, researchers are

investi-gating its possible role in preventing or inhibiting

the growth of CANCERcells

Kopp, P “Resveratrol, a Phytoestrogen Found in Red

Wine A Possible Explanation for the Conundrum of

the ‘French Paradox’?” European Journal of

Endocrinol-ogy 138 (1998): 619–620.

retinal The biologically activated form of VITAMIN

A required to form visual purple (rhodopsin), the

pigment in the retina responsible for night vision

The enzymatic conversion of vitamin A to retinal requires the trace mineral ZINC (See also NIGHT BLINDNESS.)

retinoic acid (9-cis retinoic acid) An oxidized form of VITAMIN A, believed to be a new, fat-soluble HORMONE Cis retinoic acid may guide normal embryonic development and regulate normal cell division and may be involved in regulating blood CHOLESTEROL levels CANCER is characterized by uncontrolled cell division; some patients with cer-tain kinds of cancer, such as leukemia, respond to treatments with retinoic acid In 2002 Dartmouth Medical School researchers reported a significant discovery related to retinoic acid that may be an important step in eventually finding a cure for can-cer By studying how retinoic acid works to cause remission of acute promylocytic leukemia, a deadly blood cancer, researchers discovered that when the gene UBE1L was introduced into leukemic cells, it killed them in the same way that retinoic acid does (See also ENDOCRINE SYSTEM.)

retinoid See BETA-CAROTENE; VITAMIN A

retinol See VITAMIN A

retinol equivalents (RE) See VITAMIN A

inflamma-tory disease of the joints Rheumatoid arthritis is characterized by overgrowth of joint tissue leading

to swollen immobilized joints as a result of an over-active IMMUNE SYSTEM Rheumatoid arthritis is clas-sified as an AUTOIMMUNE DISEASE in which the immune system attacks the body by developing antibodies against joint tissue An estimated 7 mil-lion people in the United States are affected by RA The much more common ailment, OSTEOARTHRITIS, represents a joint “wear and tear” arthritis and does not involve the immune system, is not an autoim-mune disease, and its cause is unrelated to rheumatoid arthritis

Rheumatoid arthritis can begin in young or middle-aged adults The triggering mechanisms are unproven It seems likely there are many con-tributing factors Infections, allergies, genetic

sus-558 respiratory chain