R 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 neighboring 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 contents 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. rancidity The process by which fats and oils 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 IRON greatly speeds the reaction of oxygen. Rancidity lowers the content of other lipids, including VITAMIN A and 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 ACIDS in 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- TION and 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 ACID can 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 BLACKBERRY and 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. Recommended Dietary Allowances (RDA) The 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 B 6 , VITAMIN B 12 ; • 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 esti- 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. National Academy of Sci- ences. red blood cells (erythrocytes) The major type of cells in blood. Red blood cells transport OXYGEN to 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*** Calcium 1000 mg 1300 mg 1200 mg 1200 mg 1200 mg 1300 mg Phosphorus 1000 mg 1300 mg 1200 mg 1200 mg 1200 mg 1250 mg (700 adult) Iron 18 mg 18 mg 18 mg 18 mg 15 mg 18 mg Iodine 150 mcg 150 mcg 150 mcg 150 mcg 150 mcg 150 mcg Magnesium 400 mg 400 mg 400 mg 400 mg 400 mg 420 mg Zinc 15 mg 10-15 mg 15 mg 15 mg 15 mg 11 mg Selenium 70 mcg – – 70 mcg 55 mcg Copper 2 mg – – 2–3 mg 1.5–3 mg 0.9 mg Manganese 2 mg – 2.5–7 mg 2.5–5 mg 2–5 mg 2.3 mg Chromium 120 mcg – – 50–200 mcg 50–200 mcg 35 mcg Molybdenum 75 mcg – 45–500 mcg 150–500 mcg 75–250 mcg 45 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. 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 MINERAL CURRENT RDI* NEW DRI** UL*** Calcium 1000 mg 1300 mg 2500 mg Iron 18 mg 18 mg 45 mg Phosphorus 1000 mg 1250 mg 4000 mg Iodine 150 mcg 150 mcg 1100 mcg Magnesium 400 mg 420 mg 350 mg# Zinc 15 mg 11 mg 40 mg Selenium 70 mcg 55 mcg 400 mcg Copper 2 mg 0.9 mg 10 mg Manganese 2 mg 2.3 mg 11 mg Chromium 120 mcg 35 mcg ND Molybdenum 75 mcg 45 mcg 2000 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 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 1875 I Street N.W. Suite 400, Washington, D.C. 20006 • (202) 872-1488 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 A 5000 IU 5000 IU 1000 RE 1000 RE 1000 RE 900 mcg (5000 IU) (3000 IU) Vitamin C 60 mg 60 mg 45 mg 60 mg 60 mg 90 mg Vitamin D 400 IU 400 IU 400 IU 10 mcg 10 mcg 15 mcg (10 mcg) (10 mcg) (10 mcg) (400 IU) (400 IU) (600 IU) Vitamin E 30 IU (20 mg) 30 IU (20 mg) 15 IU (10 mg) 10 mg (15 IU) 10 mg (15 IU) 15 mg # Vitamin K 80 mcg – – 70–140 mcg 80 mcg 120 mcg Thiamin 1.5 mg 1.5 mg 1.5 mg 1.5 mg 1.5 mg 1.2 mg Riboflavin 1.7 mg 1.7 mg 1.8 mg 1.7 mg 1.8 mg 1.3 mg Niacin 20 mg 20 mg 20 mg 19 mg 20 mg 16 mg Vitamin B 6 2 mg 2 mg 2 mg 2.2 mg 2 mg 1.7 mg Folate 0.4 mg 400 mcg 400 mcg 400 mcg 200 mcg 400 mcg food, (400 mcg) 200 mcg synthetic ## Vitamin B 12 6 mcg 6 mcg 3 mcg 3 mcg 2 mcg 2.4 mcg ### Biotin (300 mcg) 150–300 mcg 100–300 mcg 100–200 mcg 30–100 mcg 30 mcg Pantothenic acid 10 mg 5–10 mg 5–10 mg 4–7 mg 4–7 mg 5 mg Choline – – – – – 550 mg * 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 DIOXIDE concentration 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 carbon 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 VITAMIN CURRENT RDI* NEW DRI** UL*** Vitamin A 5000 IU 900 mcg (3000 IU) 3000 mcg (10,000 IU) Vitamin C 60 mg 90 mg 2000 mg Vitamin D 400 IU (10 mcg) 15 mcg (600 IU) 50 mcg (2000 IU) Vitamin E 30 IU (20 mg) 15 mg # 1000 mg Vitamin K 80 mcg 120 mcg ND Thiamin 1.5 mg 1.2 mg ND Riboflavin 1.7 mg 1.3 mg ND Niacin 20 mg 16 mg 35 mg Vitamin B 6 2 mg 1.7 mg 100 mg Folate 400 mcg (0.4 mg) 400 mcg from food, 1000 mcg synthetic 200 mcg synthetic ## Vitamin B 12 6 mcg 2.4 mcg ### ND Biotin 300 mcg 30 mcg ND Pantothenic acid 10 mg 5 mg ND Choline Not established 550 mg 3500 mg * 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 1875 I Street N.W. Suite 400, Washington, D.C. 20006 • (202) 872-1488 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 differentiates 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 B 12 , and amino acids. ANTIOXI- DANTS like VITAMIN E help 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.) red dye numbers 2, 3, 40 See ARTIFICIAL FOOD COLORS . red meat See MEAT. red tide Refers to a plankton bloom often occur- ring in marine waters during 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 shellfish 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.) Reference Daily Intake (RDI) A replacement 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) Thiamin 1.5 mg Riboflavin 1.7 mg Niacin 20 mg Calcium 1.0 gram (g) Iron 18 mg Vitamin D 400 IU Vitamin E 30 IU Vitamin B 6 2.0 mg Folic acid 0.4 mg Vitamin B 12 6 micrograms (mcg) Phosphorus 1.0 g Iodine 150 mcg Magnesium 400 mg Zinc 15 mg Copper 2 mg Biotin 0.3 mg Pantothenic acid 10 mg (Based on National Academy of Sciences’ 1968 Recommended Diet- ary Allowances.) Additions Jan. 1, 1997 Vitamin K 80 mcg Molybdenum 75 mcg Chloride 3,400 mg Manganese 2.0 mg Selenium 70 mcg Chromium 120 mcg reference protein A source of PROTEIN used 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 Histidine 23 24 Isoleucine 56 63 Leucine 95 88 Lysine 68 68 Methionine and cysteine 40 56 Phenylalanine and tyrosine 99 98 Threonine 46 49 Tryptophan 17 16 Valine 63 72 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 SUGARS or 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.) reishi mushroom (Ganoderma lucidurn, 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. renin An enzyme produced by the KIDNEYS that helps increase blood pressure. In response to a drop in BLOOD PRESSURE, renin activates the HORMONE, ANGIOTENSIN, which in turn stimulates the ADRENAL GLANDS to produce ALDOSTERONE, the hormone that directs the kidneys to retain SODIUM and 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.) rennet An extract from the stomach of 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. OXYGEN delivered 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 COPPER and 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 DIOXIDE to the volume of OXYGEN consumed. This measurement can be used to determine whether PROTEIN, CARBOHYDRATE , and FAT represent 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 WINE and 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 CANCER cells. 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. rheumatoid arthritis (RA) A chronic 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 [...]... CYTOSINE) Three of these bases occur in DNA; only uracil is unique to RNA RNA is assembled by the body from simple nutrients, and there is no dietary requirement for RNA The enzyme that synthesizes RNA (RNA polymerase) requires the trace mineral nutrient ZINC for activity (See also PURINE; PYRIMIDINE; URIC ACID.) rosemary (Rosmarinus officinalis) A perennial evergreen that grows as a shrub Rosemary has long,... Protection Act of 1996 the EPA is required to consider risks and benefits of agricultural chemicals This act created a new safety standard for pesticides in food: a reasonable certainty of no harm Public perception of risk depends in part on the source of the risk, whether it is readily apparent, and the circumstances under which it appeared Man-made hazards are less acceptable than natural (uncontrollable)... (groats), representing the husked whole grain, can be cooked like RICE Whole rye flour is dark and contains most of the nutrients of rye berries Light rye flour is a refined product, containing relatively more starch and less germ; it may be bleached Bleached rye flour is less nutritious than dark flour Cracked rye is crushed rye berries It can be cooked like cracked wheat or OATS, as a BREAKFAST CEREAL Rolled... in protein synthesis “Messenger-RNA” represents a copy of the genetic material that carries the code words specifying the amino acid sequence characteristic of each protein “Ribosomal RNA” occurs in ribosomes, cytoplasmic particles that combine with messenger RNA and provide the site of protein synthesis A third family of RNA is “transfer RNA,” which carries activated amino acids to assemble proteins... 0.33 mg of riboflavin per day for a typical American Riboflavin is nontoxic; excesses are excreted and turn urine yellow Requirements The RECOMMENDED DIETARY ALLOWANCE (RDA) of riboflavin is 1.7 mg per day for men and 1.3 mg per day for women between the ages of 25 and 50 The requirement is somewhat higher for women who are pregnant or breast-feeding Anyone with a severely compromised diet is prone to... (LIVER, kidney, and heart); dairy products (MILK, CHEESE, YOGURT); and BREWER’S YEAST BREAKFAST CEREAL, enriched flour, almonds, lean meat, raw mushrooms, wheat bran, enriched cornmeal, soybean flour, and dark green leafy VEGETABLES are good sources Fifty percent of the riboflavin in milk can be lost within two hours after exposure to light Storing milk in cartons rather than in glass bottles markedly reduces... Transfer RNAs “read” code words in the messenger RNA, align amino acids in the proper sequence and permit amino acids to be joined together Thus transfer RNAs help translate the language of DNA into the language of proteins in all cells In terms of composition, RNA consists of phosphate; the simple sugar, ribose; and four nitrogencontaining compounds (ADENINE, GUANINE, uracil, and CYTOSINE) Three of. .. Use of these strains, better irrigation, risk due to chemicals in food and water 561 increased use of chemical fertilizers and synthetic pesticides created a dramatic increase in grain production in Asia, South America, and Africa Rice is classified according to size: Short-grain rice is oval in shape, contains less AMYLOSE, a straight-chain form of STARCH, and is sticky when cooked Medium-grain rice... corn Parboiled rice represents rough rice that has been soaked, steamed, and dried to loosen husks, which are removed by milling Greater amounts of nutrients are retained than in white rice Rice is used as a breakfast food (puffed rice, flakes, crispies), rice flour, flaked rice, rice-based baby food, rice oil, and rice bran Rice bran contains fiber that can help reduce blood cholesterol levels and rice... production of cereal grains and ranks eighth in the world Northern Europe remains a major region for rye production Popularity in the United States has declined steadily since 1920, and the United States produces 2 percent of the world rye crop Ergot, a fungus that produces a poisonous substance that can cause convulsions, can infect rye Limits have been established for ergot contamination Rye berries . osteoporosis, and CORONARY ARTERY DISEASE. The DRIs incorporate the RDAs along with three other nutrient-based reference values: the esti- mated average requirement (the daily intake esti- mated. 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 DIOXIDE to the volume. ACID. Rhubarb stalks are cooked in pies, sauces, rhubarb crumble, and other baked goods, jams, and preserves, and they can be fermented to produce wine. Rhubarb is extremely tart and requires the