Nutrition and Weight Control - Basic nutritional requirements

The process by which food is converted into useful energy is called metabolism . It begins with chemical processes in the gastrointestinal tract which change plant and animal food into less complex components so that they can be absorbed to fulfill their various functions in the body— growth, repair, and fuel. Different foods have different energy values, measured in calories. An ideal diet for the average healthy individual provides the highest nutritional benefits from the fewest number of calories. Information on the protein, fat, and carbohydrate content in specific foods, as well as the number of calories, may be obtained by consulting the tables “Nutrients in Common Foods.” The Metric Equivalents table converts spoon and cup measures into metric measures.

Protein

Of the several essential components of food, protein is in many ways the most important. This is so not only because it is one of the three principal sources of energy, but also because much of the body's structure is made up of proteins. For example, the typical 160-pound man is composed of about 100 pounds of water, 29 pounds of protein, 25 pounds of fat, 5 pounds of minerals, 1 pound of carbohydrate, and less than an ounce of vitamins. Because the muscles, heart, brain, lungs, and gastrointestinal organs are made up largely of protein, and since the protein in these organs is in constant need of replacement, its importance is obvious.

The recommended dietary allowance for protein is 0.8 g/Kg of body weight per day for persons aged 15 and up and 1 g/Kg of body weight for children under 15. (To convert your weight from pounds to kilograms, divide by 2.2. Thus a woman weighing 130 pounds weighs about 59 kilograms and needs about 47 grams of protein a day. A man weighing 175 pounds needs about 64 grams of protein a day.) Most Americans, however, eat about twice the amount they need, and while more may sound better, too much is too much. Your body uses what it needs. Some excess protein is excreted as urine; the rest is converted to fat.

Chemically, proteins are varying mixtures of amino acids that contain various elements, including nitrogen. There are 22 different amino acids that are essential for the body's protein needs. Nine of these must be provided in the diet and are thus called essential amino acids; the rest can be synthesized by the body itself.

Meat, fish, poultry, eggs, and milk or milk products are the primary protein foods and contain all of the necessary amino acids; they are therefore called complete proteins. Grains and vegetables are partly made up of protein, but more often than not, they do not provide the whole range of amino acids required for proper nourishment. When properly combined, however, vegetable proteins, too, can be complete. For example, mixing rice and dried beans provides the same quality of protein as a steak (with a lot less fat).

One gram of protein provides four calories of energy.

Carbohydrates

Carbohydrates are another essential energy source. Called starches or sugars , they are present in large quantities in grains, fruits, and nuts. As complex carbohydrates , or polysaccharides , they are found in the foods named and particularly in breads, breakfast cereals, flours, pastas, barley legumes, rice, and starchy vegetables. Simple carbohydrates , or mono- or disaccharides, are found in such foods as table sugars, candy, pastries, and soft drinks.

Complex carbohydrates are primary sources of calories, nutrients, and fiber—for such purposes as muscle contraction, weight reduction, and control of sodium and cholesterol. Simple carbohydrates, on the other hand, are pure sources of calories and contain little nutritional value. It is for this reason that they are often termed “empty” calories. Lack of adequate carbohydrates means the body will begin to convert body fat or protein into sugar.

Although there is no absolute dietary requirement for carbohydrates, it is generally recommended that more than half the energy requirement beyond infancy be provided by complex carbohydrates. One gram of carbohydrate provides four calories of energy. Thus the average man consuming about 2,900 calories per day should consume about 360 grams of carbohydrate. The average woman consuming about 2,200 calories per day should consume about 275 grams of carbohydrate.

Fats

Fats are a chemically complex food component composed of glycerol (a sweet, oily alcohol) and fatty acids. Fats exist in several forms and come from a variety of sources. One way to think of them is to group them as visible fats, such as butter, salad oil, or the fat seen in meat, and as invisible fats, which are mingled, blended, or absorbed into food, either naturally, as in nuts, meat, or fish, or during cooking. Another way is to think of them as solid at room temperature (fats), or as liquid at room temperature (oils).

Saturated and Unsaturated

Fats are also classified as saturated or unsaturated . This is a chemical distinction based on the differences in molecular structure of different kinds of fat. If the carbon atoms in a fat molecule are surrounded or boxed in by hydrogen atoms, they are said to be saturated. This type of fat tends to be solid at room temperature, and high consumption of it increases the cholesterol content of the blood, which can lead to heart disease. Unsaturated fats, such as those found in fish and vegetable oils, contain the least number of hydrogen atoms and do not add to the blood cholesterol content. They are either monounsaturated or polyunsaturated . In general, fats in foods of plant origin are more unsaturated than in those of animal origin (except for coconut and palm oils, which are highly saturated). It is recommended that you consume no more than 30 percent of your daily calories from fats; 10 percent of each of the three types, or, for our average man, about 32 grams total; for our average woman, about 24 grams total.

Fats play several essential roles in the metabolic process. First of all, they provide more than twice the number of calories on a comparative weight basis than do proteins and carbohydrates (one gram of fat contains nine calories). They also can be stored in the body in large quantities (in adipose tissue) and used as a later energy source. They serve as carriers of the fat-soluble vitamins A, D, E, and K, and—of no little importance—they add to the tastiness of food.

Vitamins

Vitamins , which are present in minute quantities in foods in their natural state, are essential for normal metabolism and for the development and maintenance of tissue structure and function. In addition to the fat-soluble vitamins noted above, there are a number of B vitamins, as well as vitamin C, also called ascorbic acid . If any particular vitamin is missing from the diet over a sufficiently long time, a specific disease will result.

Vitamin A

Vitamin A is essential for vision, growth, cell growth and development, reproduction, a strong immune

Men	Calories
Guidelines for average daily calorie consumption by men and women. With increasing use of labor-saving devices, most Americans fall into the sedentary category.
Sedentary	2,500
Moderately active	3,000
Active	3,500
Very active	4,250
Women	Calories
Sedentary	2,100
Moderately active	2,500
Active	3,000
Very active	3,750

Type of Activity	Calories Per Hour
Sedentary: reading, sewing, typing, etc.	30–100
Light: cooking, slow walking, dressing, etc.	100–170
Moderate: sweeping, light gardening, making beds, etc.	170–250
Vigorous: fast walking, hanging out clothes, golfing, etc.	250–350
Strenuous: swimming, bicycling, dancing, etc.	350 and more

Sample Menus
	1,500 Calories	1,800 Calories	2,000 Calories
From the Clinical Center Diet Manual , Clinical Center Nutrition Department, National Institutes of Health, Department of Health and Human Services.
Breakfast	1 serving fruit/juice	1 serving fruit/juice	1 serving fruit/juice
	1 slice toast	1 slice toast	1 slice toast
	1 serving egg or substitute	1 serving egg or substitute	1 serving egg or substitute
	1 serving margarine	1 serving cereal	1 serving cereal
	1 cup skim milk	1 serving margarine	1 serving margarine
	coffee/tea	1 cup skim milk	1 cup skim milk
		coffee/tea	coffee/tea
Lunch	2-3 ounces meat	2-3 ounces meat	2-3 ounces meat
	1 serving potato or	1 serving potato or	1 serving potato or
	substitute	substitute	substitute
	1 serving bread	1 serving bread	1 serving bread
	vegetables	vegetables	vegetables
	salad/non-fat dressing	salad/non-fat dressing	Salad/non-fat dressing
			2 servings fruit/juice
	2 servings fruit	2 servings fruit/juice	1 serving margarine
	1 serving margarine	1 serving margarine	1 cup skim milk
	coffee/tea	coffee/tea	coffee/tea
Dinner	2-3 ounces meat	2-3 ounces meat	2-3 ounces meat
	1 serving potato or substitute	1 serving potato or substitute	2 servings potato or substitute
	1 serving bread	1 serving bread	1 serving bread
	vegetables	vegetables	vegetables
	salad/non-fat dressing	salad/non-fat dressing	Salad/non-fat dressing
			1 serving fruit/juice
	1 serving fruit	2 servings fruit/juice	2 servings margarine
	2 servings margarine	2 servings margarine	coffee/tea
	coffee/tea	coffee/tea
Snack	3 graham crackers	1 ounce meat	1 ounce meat
	1 cup skim milk	1 slice bread	1 slice bread
		1 serving reduced-fat mayonnaise	1 serving reduced-fat mayonnaise
		1 cup skim milk	non-alcoholic beverage

system, and healthy hair, skin, and mucous membranes.

Vitamin A is fat soluble and is therefore stored by the body (in the liver). It comes in two forms: retinol, found only in animal foods (chiefly liver), and beta-carotene, found in fruits and vegetables (chiefly deep green or orange ones like spinach and sweet potatoes). Retinol is instantly available for bodily use, while beta-carotene must be converted by the body into retinol before it can be used. (Because the body will not convert excess beta-carotene into retinol, there is no danger of overdosing on this form of vitamin A Retinol, however, can be extremely toxic at high levels.)

Symptoms of vitamin A deficiency include dry rough skin, slow growth, night blindness, thickening of bone, and increased susceptibility to infection. Vitamin A deficiency is rare in the United States.

Formerly measured in International Units (IU), vitamin A content is now expressed retinol equivalents (RE). One RE equals 10 IU of beta-carotene and 3.33 IU of retinol. The Recommended Daily Allowance (RDA) for vitamin A for adult males is 1000 RE and for adult women, 800 RE.

Vitamin D

Vitamin D is essential for proper metabolism of calcium, which is primarily responsible for the healthy growth of bones and teeth.

Vitamin D is fat soluble and therefore excessive intake can be toxic. It is consumed chiefly as an addition to milk and is also manufactured by the body by a reaction of sunlight on sterols present in the skin.

The major deficiency disease of vitamin D in children is rickets (deformation of the skeleton) and in adults excessive bone loss and fractures.

The RDA for adults over 24 is 5 mi-crograms.

Vitamin E (tocopherol)

Vitamin E is essential for healthy nerve function and reproduction.

Vitamin E is found principally in plant oils, particularly wheat germ oil and nuts. It is fat soluble, but there is little danger of toxicity because absorption by the body is relatively inefficient.

Vitamin E is measured in tocopherol equivalents (TE). The RDA for adult males is 10 TE and for adult women 8 TE. Deficiencies in a normal diet are rare.

Vitamin K

Vitamin K is essential for proper clotting of the blood.

Vitamin K is fat soluble and is found primarily in green leafy vegetables. Another form of the compound is synthesized by intestinal bacteria. Like vitamin E, there is little danger from ingesting too much vitamin K, and most diets provide an adequate supply.

The RDA for adult males over age 24 is 80 micrograms and for adult women 65 micrograms.

Vitamin C (ascorbic acid)

Vitamin C is essential for healthy skin, bones, teeth, and muscles, for producing and maintaining collagen, and for fighting infection.

Vitamin C is water soluble and therefore must be ingested every day. It is widely available in a variety of colorful fruits and vegetables, such as peppers, broccoli, cabbage, oranges, strawberries, and tomatoes. Unfortunately, vitamin C is also the most unstable of all vitamins and minerals: it is easily destroyed by heat and oxygen, and thus care should be taken in cooking and storing of fruits and vegetables.

The classic vitamin C deficiency disease is scurvy, typified by the wasting away of muscles, wounds and bruises that don't heal, and bleeding, deteriorating gums. Milder forms of vitamin C deficiency produce milder versions of these symptoms. Vitamin C deficiency has also been linked to such health problems as the common cold, anemia, atherosclerosis, asthma, cancer of the stomach and esophagus, infertility in males, rheumatoid arthritis, and cataracts.

Vitamin C is measured in milligrams (mg). The RDA for adults is 60 mg. Megadoses of vitamin C are often recommended to fight colds or as a general preventive measure against disease, although the body only uses as much as it needs; the rest is excreted in the urine. Toxicity is rarely a problem.

Thiamin (vitamin B ₁ )

Thiamin is essential for the proper metabolism of carbohydrates and for a healthy nervous system.

Thiamin is water soluble and is found primarily in cereals, wheat germ, port, and nuts. It is strongly susceptible to destruction during cooking. Deficiency is not common among the general population, but studies have shown heavy drinkers, pregnant women, and the elderly to be more deficient. Severe thiamin deficiency results in beriberi, a disease that weakens the body, disables the mind, and permanently damages the heart. Symptoms of deficiency include loss of appetite, nausea, vomiting, constipation, depression, fatigue, poor eye-hand coordination, irritability, headaches, and anxiety.

Thiamin is measured in milligrams. The RDA for adult males is 1.5 mg and for adult women 1.1 mg. Danger of toxicity is rare as excess thiamin is excreted in urine.

Riboflavin (vitamin B ₂ )

Riboflavin is essential for growth and repair of tissues and aids in DNA synthesis. It helps metabolize proteins, fats, and carbohydrates.

Most Americans get plenty of this water-soluble vitamin, which is readily found in liver, eggs, and milk products. Studies have found that children in low-income families, however, are less likely to get enough riboflavin. Signs of deficiency include a purplish-colored tongue; cracks at the corners of the mouth; sores and burning of the lips, mouth, and tongue; itchy inflamed eyelids; flaky skin around the nose, ears, eyebrows, or hairline; and light sensitivity of eyes. Deficiency in riboflavin often means deficiency in other B vitamins as well. Cataracts, birth defects, and anemia have been linked to riboflavin deficiency.

Unlike vitamin C and thiamin, riboflavin is not easily destroyed by cooking, although adding baking soda to vegetables when cooking creates an alkaline solution that destroys it. Risk of toxicity is very low, and excess riboflavin is excreted in the urine.

Riboflavin is measured in milligrams. The RDA for adult males is 1.7 mg and for adult women 1.3 mg.

Niacin (vitamin B ₃ )

Niacin is essential for the release of energy from carbohydrates, fats, and proteins and for the formation of DNA.

Most Americans get plenty of niacin from their diets; only heavy drinkers are at risk of deficiency. Severe deficiencies of niacin result in pellagra, a disease virtually wiped out in the United States since the 1930s with the advent of fortified flour and cereals with the vitamin.

Niacin is widely available in a variety of plant and animal foods, including fish, liver, turkey, cereals, and peanuts. The body is also able to convert the amino acid tryptophan into niacin, and thus proteins high in tryptophan also provide plenty of niacin.

Niacin in measure in milligrams (60 mg of tryptophan equal 1 mg of niacin). The RDA for adult males is 19 mg. and for women 15 mg.

Vitamin B ₆

Vitamin B ₆ is essential for fat and carbohydrate metabolism and for the formation and breakdown of amino acids. It also helps regulate blood glucose levels and is needed to synthesize hemoglobin.

Vitamin B ₆ occurs in three forms: pyridoxine, pyridoxal, and pyridoxam-ine, which are converted by the body into pyridoxal phosphate and pyridox-amine phosphate. It is most readily found in nuts, kidney, liver, eggs, pork, poultry, dried fruits, and fish.

Although few Americans get the full RDA of vitamin B ₆ , there is no evidence of corresponding overt deficiency symptoms. The following health problems, however, have been linked to B ₆ deficiency: asthma, carpal tunnel syndrome, cancer (melanoma, breast, and bladder), diabetes, coronary heart disease, premenstrual syndrome, sickle-cell anemia, and aging and dementia.

In moderate doses B ₆ is not toxic. Although excessive amounts of this water-soluble vitamin are to a great extent flushed out of the body in the urine, high doses have produced neurological disturbances such as numbness in the hands, feet, and mouth.

Vitamin B ₆ is measured in milligrams. The RDA for adult men is 2 mg and for women 1.6 mg.

		Vit. A	Vit. D	Vit. E	Vit. K
	Age	(meg RE)	(meg)	(mgTE)	(meg)
Infants	0 to .5	375	7.5	3	5
	.5 to 1	″	10	4	10
Children	1 to 3	400	″	6	15
	4 to 6	500		7	20
	7 to 10	700		″	30
Males	11 to 14	1,000	″	10	45
	15 to 18	″			65
	19 to 24	″	″	″	70
	25 to 50	″	5		80
	51 +	″	″	″	″
Females	11 to 14	800	10	8	45
	15 to 18	″	″	″	55
	19 to 24	″			60
	25 to 50	″	5		65
	51 +	″	″	″	″
Pregnant		″	10	10
Nursing	1st 6 months	1,300		12
	2nd 6 months	1,200		11

Vitamin B ₁₂

Vitamin B ₁₂ is important for normal growth, healthy nerve tissue, and normal blood formation.

Most Americans get plenty of B ₁₂ . It is found chiefly in animal foods: meat, fish, eggs, and milk products. Only strict vegetarians (vegans), who eat none of these foods are in danger of deficiency. Problems for everyone arise with age, however; the stomach may become less able to absorb B ₁₂ and deficiency may result. Pernicious anemia is the classic B ₁₂ deficiency disease and may take years to appear. Other health problems that may be linked to B ₁₂ deficiency include infertility, nervous system disorders, and walking difficulties.

Cooking results in few losses of B ₁₂ , and toxicity is not a danger. The RDA for B ₁₂ for adults is 2 micrograms.

Folacin (folic acid, or folate)

Folacin is essential for cell growth and division.

Women, especially pregnant women, and alcoholics are most likely to be folacin deficient. Signs of deficiency include anemia, weakness, pallor, headaches, forgetfulness, sleeplessness, and irritability. Vitamin B ₁₂ deficiency can aggravate folacin deficiency because B ₁₂ is essential to release folacin from bodily storage. Other health problems that may be associated with folacin deficiency include depression, dementia, neuropsychological disorders, toxemia of pregnancy, infections, and fetal damage.

Folacin is widely distributed in fruits and vegetables, but it is easily destroyed during cooking and storage. The RDA for folacin for adult men is 200 micrograms and for women, 180 micrograms.

Biotin

Biotin is essential for overall growth and well-being. It is important in the metabolism of fats and in the utilization of carbon dioxide.

The best sources of biotin are liver, egg yolks, soy flour, cereals, and yeast. It is also produced by intestinal bacteria, although it is not known whether this form is readily absorbed by the body. Deficiencies are most often produced by the ingestion of large amount of raw egg white, which contains a biotin-binding protein called avidin that prevents the absorption of biotin. Symptoms of deficiency include nausea, vomiting, swelling of the tongue, pallor, depression, hair loss, and dry scaly dermatitis.

	Age	Vit. C	Thiamin	Riboflav.	Niacin	Vit. B6	Folate	Vit. B12
		(mg)	(mg)	(mg)	(mg)	(mg)	(meg)	(meg)
Infants	0 to .5	30	0.3	0.4	5	0.3	25	0.3
	.5 to 1	35	0.4	0.5	6	0.6	35	0.5
Children	1 to 3	40	0.7	0.8	9	1	50	0.7
	4 to 6	45	0.9	1.1	12	1.1	75	1
	7 to 10	″	1	1.2	13	1.4	100	1.4
Males	11 to 14	50	1.3	1.5	17	1.7	150	2
	15 to 18	60	1.5	1.8	20	2	200	″
	19 to 24	″	″	1.7	19	″	″	″
	25 to 50	″	″	″	″	″	″	″
	51 +	″	1.2	1.4	15	″	150	″
Females	11 to 14	50	1.1	1.3	″	1.4	180	″
	15 to 18	60	″	″	″	1.5	″	″
	19 to 24	″	″	″	″	1.6	″	″
	25 to 50	″	1.1	″	″	″	″	″
51 +		″	1	1.2	13	″	″	″
Pregnant		70	1.5	1.6	17	2.2	400	2.2
Nursing	1st 6 months	95	1.6	1.8	20	2.1	280	2.6
	2nd 6 months	90	″	1.7	20	″	260	″

The RDA for adults is a wide range: from 30 to 100 micrograms. Toxicity from a normal diet is not a concern.

Pantothenic acid

Pantothenic acid is essential for general growth and well-being. It is an important component in a number of metabolic reactions such as the release of energy from carbohydrates, fats, and proteins and the synthesis of sterols and steroid hormones.

Pantothenic acid is widely distributed among foods, chiefly animal tissues, cereals, and legumes. Evidence of dietary deficiency of pantothenic acid has not been clinically recognized in humans, and there is no specific disease associated with pantothenic acid deficiency.

Pantothenic acid is measured in milligrams. There is no RDA, but daily consumption by adults of between 4 and 7 mg is considered safe. Toxicity from a normal diet is not a concern.

Minerals

Minerals are another component of basic nutritional needs. All living things extract them from the soil, which is their ultimate source. Like vitamins, they are needed for normal metabolism and must be present in the diet in sufficient amounts for the maintenance of good health. The essential minerals are calcium, phosphorus, magnesium, iodine, iron, zinc, selenium, molybdenum, copper, manganese, fluoride, and chromium.

Calcium

Calcium is essential for bone growth, development, and retention as well as for proper nerve conduction, muscle contraction, blood clotting, and membrane permeability.

Dairy products are the primary sources of calcium, but the mineral is also found in green leafy vegetables and soft bones, such as those of sardines and salmon. Maximum calcium ingestion is extremely important during the years from birth to age 25, when the body reaches its peak bone mass. Deficiencies are most common in women and have been linked to the development of osteoporosis in the later years.

The RDA for calcium for children between the ages of 11 and 24 is 1,200 mg. For adults over 24 the RDA is 800 mg. Ingestion of very large amounts of calcium may inhibit the absorption of iron, zinc, and other essential minerals.

Phosphorus

Phosphorus is a structural component of all cells. It is a part of DNA, and is therefore essential in the growth, maintenance, and repair of all body tissues. It is also critical for energy transfer and production.

Phosphorus is present in nearly all foods, principally cereals and proteins. Deficiency is a serious concern only for premature infants fed exclusively human milk.

The RDA for phosphorus is the same as that for calcium. Toxicity from a normal diet is not a concern.

Magnesium

Like phosphorus, magnesium is a structural component in soft tissue cells and is therefore important in the growth, maintenance, and repair of these tissues. It is also important in energy production, lipid and protein synthesis, the formation of urea, muscle relaxation, and in the prevention of tooth decay.

The best sources of magnesium are nuts, legumes, unmilled grains, and green vegetables. Deficiencies from a normal diet are rare and are related instead to various diseases such as those of the gastrointestinal tract, kidney dysfunction, and malnutrition and alcoholism. Symptoms of deficiency include weakness, confusion, personality changes, muscle tremor, nausea, lack of coordination, and gastrointestinal disorders.

The RDA for adult men is 350 mg and for adult women 280 mg.

Iodine

Iodine is an essential component of thyroid hormone, which is important in cellular reactions, metabolism, and growth and development.

Iodized salt and water are the most common sources, and most animal foods contain adequate supplies depending on the soil quality and the amount of iodine added to animal feeds. Iodine is also added in the processing of bread dough. Deficiencies in the United States is not common. The classic deficiency disease in adults is goiter. Iodine deficient fetuses are at a risk of developing cretinism.

The RDA for iodine for adults is 150 micrograms.

Iron

As an essential component of hemoglobin, iron is necessary for the proper transfer of oxygen to cells. It is also important for energy production and collagen synthesis.

Many Americans don't get enough iron. Women and very young children get the least, followed by the elderly. Iron deficiency leads to anemia: muscles become weak, fatigue, listlessness, and a tendency to tire easily set in. Even mild iron deficiency, however, can affect a person's intellectual capabilities, especially children's. Symptoms of deficiency in children include irritability, hyperactivity, learning problems, shortened attention span, poor motivation, and poor intellectual performance.

There are two types of iron, heme and nonheme. Heme comes from animal foods and is much more readily absorbed than nonheme iron, which comes from vegetables. When eaten together, however, the rate of absorption for nonheme iron increases significantly. Also, iron eaten with just a little vitamin C dramatically increases its absorption. Tannins (in tea and red wine) block iron absorption. Iron-rich foods include liver and other organ meats, beef, dried fruits, legumes, dark green leafy vegetables, prune juice, and whole grain cereals.

The RDA for adult males is 10 mg and for adult women 15 mg. There is little danger of toxicity from a normal diet, although some people have an inherited defect in regulating iron absorption and can easily get too much.

Zinc

Zinc is essential for cell multiplication, tissue regeneration, sexual maturity, and proper growth. It is also important as a cofactor in more than 20 enzymatic reactions and serves as a binder in many others.

Severe zinc deficiency is not a problem in the United States, but the effects of mild deficiency—common especially in children, women, and the elderly—on overall health are feared to be widespread. Signs of deficiency include loss of appetite, stunted growth in children, skin changes, small sex glands in boys, delayed sexual maturation, impotence, loss of taste sensitivity, white spots on fingernails, delayed wound-healing, dull hair color.

Animal foods are good sources of zinc as are oysters, milk, egg yolks, and whole grains. Toxicity is rare. The RDA for adults is 12 mg.

Selenium

Selenium functions in a similar way to vitamin E, as an antioxidant helping to protect cells from destruction by toxic agents. Its consumption has also been associated with lower incidences of cancer and heart disease.

Good sources of selenium include whole grains, seafood, liver, kidney, meat, seeds, and nuts. Deficiency may be a problem in areas with selenium-poor soils. Selenium is toxic at higher than trace amounts. The RDA for adult males is 70 micrograms and for adult women 55 micrograms.

Molybdenum

Molybdenum is essential in the function of certain enzyme systems and is also necessary in iron metabolism.

Sources of molybdenum include meats, whole grains, legumes, leafy vegetables, and organ meats. The molybdenum content of vegetables varies widely depending on the content of the soil in which they were grown. Deficiency is not known in humans. Ingesting more than trace amounts is not recommended. The RDA for adults is between 75 and 250 micrograms.

Copper

Copper is important as a cofactor in several enzyme systems and as a catalyst in the synthesis of hemoglobin. It also aids in collagen formation and is involved in the synthesis of phospholipids, which maintain health nerve fibers.

Copper deficiency is believed to be more common than once thought, and it has been linked to heart disease, central nervous system disorders, anemia, and bone disorders. Good sources of copper include shellfish, liver, nuts and seeds, meats, and green leafy vegetables. Copper supplements are not recommended because they can interfere with other minerals, and copper is toxic at more than trace amounts. The RDA for copper is 1.5 to 3 mg.

Manganese

Manganese has a variety of functions, some that other minerals can perform in its place. It is known to play a role in such things as collagen formation, urea formation, synthesis of fatty acids and cholesterol, digestion of proteins, normal bone formation and development, and protein synthesis.

Manganese deficiency has not been observed in humans. Sources of manganese include liver, kidney, spinach, whole grain cereals and breads, dried peas and beans, and nuts. Excessive intake of manganese can interfere with iron absorption. More than trace amounts of manganese are not recommended. The RDA is 2 to 5 mg.

Fluoride

Fluoride is essential for the development of healthy teeth and bones and the prevention of tooth decay.

Fluoride deficiency shows up in increased incidences of tooth decay. Fluoridated water is a most common source of fluoride for many people. For those without access to such water fluoride tablets or toothpaste are helpful. Fish, tea, milk, and eggs are also sources of fluoride. The RDA for adults is between 1.5 and 4 mg.

Chromium

Chromium is important for maintaining normal glucose metabolism. It also acts as a cofactor for insulin.

Chromium deficiency can show up in the form of glucose intolerance in malnourished children and in some diabetics. Sources of chromium include whole grains, brewer's yeast, meats, and cheeses. Hard water also contains chromium. Chromium intake should not exceed trace amounts. The RDA for adults is between 50 and 200 micrograms.

Fiber

Fiber in the diet is important for proper elimination. It provides bulk, and its use has been linked to the prevention of many health problems: constipation, appendicitis, colon cancer, diverticular disease, spastic colon, hiatal hernia, varicose veins, hemorrhoids, coronary heart disease, high blood pressure, gallstones, diabetes, obesity, ulcerative colitis, and Crohn's disease.

Fiber is found almost exclusively in plant foods and comes in basically two types: water soluble or water insoluble. Soluble fiber is found primarily in fruits and vegetables and in oat bran in the form of gums and pectin and affects the way the body metabolizes sugars and fats. Insoluble fiber is primarily associated with whole grains, the traditional ‘bran,’ such as wheat bran and rice bran, and is the fiber we think of when we think of laxatives. Generally, the less processed the food, the higher it is in either kind of fiber.

Fiber in high doses can affect the absorption of other vitamins and minerals as well as cause flatulence, bloating, nausea, diarrhea, and impaction or rupture of the bowl. Daily consumption of 35 to 40 grams of fiber is recommended for optimum health and safety.

Water

Water is not really a food in the fuel sense, but it is in many ways a crucial component of nutrition: the body's need for water is second only to its need for oxygen. It makes up from 55 to 65 percent of the body's weight, and is constantly being eliminated in the form of urine, perspiration, and expired breath. It must therefore be replaced regularly, for while a person can live for weeks without food, he can live for only a few days without water.

Normally, the best guide to how much water a person needs is his sense of thirst. The regulating mechanism of excretion sees to it that an excessive intake of water will be eliminated as urine. The usual water requirement is on the order of two quarts a day in addition to whatever amount is contained in the solids which make up the daily diet.