Major Nutrients: Functions and Sources

MAJOR NUTRIENTS: FUNCTIONS AND SOURCES

Fat-Soluble Vitamins	Important Sources	Physiological Roles
Vitamin A (retinol, beta carotene)	Milk, butter, fortified margarine, whole milk Cheese, liver, egg yolk (retinol) Green leafy and stem vegetables, yellow fruits and vegetables (carotene), eg, spinach, asparagus, broccoli, carrots, apricots, and cantaloupe	Maintains normal vision in dim light, healthy skin, and mucous membranes Essential for normal skeletal and tooth development
Vitamin D (calciferol)	Exposure to sunlight, fortified foods, fish liver oils	Maintains blood calcium and phosphorus levels Required for proper bone development
Vitamin E (tocopherol)	Vegetable oils Whole grains, wheat germ Leafy vegetables Egg yolk Legumes, nuts (especially almonds, peanuts, pecans, walnuts), sunflower seeds	Protects the integrity of normal cell membranes Assists in prevention of hemolysis of red blood cells Protects vitamin A, acting as an antioxidant
Vitamin K	Lettuce, spinach (green leafy vegetables), kale, cauliflower, cabbage Egg yolk Soybean oil Liver	Produces prothrombin in normal blood clotting
Water-Soluble Vitamins	Important Sources	Physiologic Roles
Ascorbic acid (vitamin C)	Citrus fruits, strawberries, cantaloupe, tomatoes, sweet peppers, cabbage, potatoes, kale, parsley, turnip greens, broccoli	Maintains integrity of capillaries Promotes healing of wounds and fractures Aids tooth and bone formation Increases iron absorption Protects folic acid Helps form collagen for healthy connective tissue
Thiamin (vitamin B1)	Pork, liver, chicken, fish, beef Whole grains, wheat germ, dried yeast, enriched cereal products Nuts and lentils	Metabolizes carbohydrates for energy Provides function of nerve cell membranes
Riboflavin (vitamin B2)	Milk Liver, meat, fish, eggs Enriched cereal products Green leafy vegetables	Metabolizes carbohydrates, proteins, and fats for energy Closely related to the metabolism of protein
Niacin	Liver, poultry, meat, fish, eggs Whole grains, enriched cereal products Peanuts, peanut butter	Metabolizes carbohydrate for energy
Pyridoxine (vitamin B6)	Pork, organ meats, meat, poultry, fish, legumes, seeds Whole grains	Metabolizes protein Converts tryptophan to niacin Synthesizes hemoglobin Maintains integrity of central nervous system

Water-Soluble Vitamins	Important Sources	Physiologic Roles
Vitamin B12 (cyanocobalamin)	Animal foods only: liver, meat, salt-water fish, oysters, eggs Milk	Essential for red blood cell maturation and normal function of all body cells (especially nervous system, gastrointestinal tract and bone marrow)
Folate	Green leafy vegetables Liver, beef, fish, dry beans, lentils Whole grains	Essential for DNA synthesis and synthesis and maturation of red blood cells
Pantothenic acid	Animal sources (esp. organ meats, egg yolk, and meat) Whole grains Legumes Yeast	Responsible for metabolism of carbohydrates, proteins, and fats for energy; formation of some hormones, hemoglobin, and nerve-regulating substances
Biotin	Organ meats, egg, yolk, legumes, nuts	Synthesizes fatty acids Helps in metabolism of carbohydrates for energy
Minerals	Important Sources	Physiologic Roles
Calcium	Milk Hard cheeses, eg, cheddar, Swiss, mozzarella, and provolone Yogurt, ice cream, cottage cheese Turnip and mustard greens, collards, kale, broccoli, cabbage	Maintains strength of bones and teeth Involved with transmission of nerve impulses, muscle contractions and relaxation, blood clotting, structure and function of cell membranes, and absorption of vitamin B12
Phosphorus	Milk and milk products Meat, poultry, fish and eggs Whole grain cereals and flours Nuts and legumes	Essential for structure of bones and teeth; release of stored energy; structure of RNA and DNA; cell permeability; and metabolism of carbohydrates, fats, and proteins
Magnesium	Whole grain breads and cereals Soybeans, nuts, dry beans and peas, green leafy vegetables	Fundamental to the production of energy, calcium, and phosphorus metabolism in bone; maintenance of the function and structural integrity of heart muscle as well as other muscles and nerves
Sodium	Use of salt at the table and in cooking Processed foods Milk Eggs, meat, poultry, fish Smoked meats Olives, pickles, soy sauce	Maintains normal osmotic pressure water balance, normal irritability of nerve cells and contraction of muscles, and permeability of the cell membrane
Potassium	Meats, poultry, fish, (especially veal and salmon) Fruits and vegetables (especially bananas, potatoes, tomatoes, and citrus fruits) Whole grain cereals	Maintains normal osmotic pressure and fluid balance Required to store energy within the cell Key to transmission of nerve impulse and contraction of muscle fibers, especially the heart muscle
Chloride	Use of salt at the table and in cooking	Regulates osmotic pressure, water balance, and acid-base balance of extracellular fluid Is a component of hydrochloric acid in the gastric juice

Trace Elements	Important Sources	Physiologic Roles
Iron	Liver, meat, fish and poultry Whole grain and enriched cereals Legumes Green leafy vegetables Eggs Dried fruit Foods cooked in iron pots and skillets (especially foods with a high acid content)	Essential to the formation of hemoglobin in blood and myoglobin in muscles, which supply oxygen to cells
Zinc	Animal products (especially liver and oysters) Beef, lamb, pork Whole grain cereals Legumes Peanuts Peanut butter	Essential in wound healing, synthesis of proteins, mobilization of vitamin A from liver, normal cellular immune functions, and normal growth of genital organs
Copper	Organ meats Shellfish (especially oysters and crabs) Whole grain cereals Hickory and brazil nuts, sesame and sunflower seeds Legumes (soybeans, kidney, navy, lima beans)	Essential for formation of red blood cells and the utilization of iron, production of energy, cell protection against oxidative damage, and synthesis of connective tissue
Iodine	Iodized salt used at the table and in cooking	Part of thyroid hormones Influences physical and mental growth, functioning of nervous and muscle tissues, circulatory activity, and metabolism of all nutrients
Fluoride	Fluoridated water Seafood	Increases deposit of calcium, which strengthens the bone and reduces the acid in the mouth, therefore decreasing tooth decay
Chromium Manganese Molybdenum Selenium Nickel Silicon Vanadium	Present in very small amounts in plant foods (ie, whole grains, dried beans and peas, nuts, seeds, fresh fruits and vegetables) Animal foods (meat, fish, poultry, eggs)	Essential as components of enzymes and hormones

Manual of Clinical Nutrition Management
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