chapter 7 - Chapter Summary for Nutrition Concepts and...

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Chapter Summary for  Nutrition: Concepts and Controversies  11e Chapter 7 – The Vitamins Vitamins are essential, noncaloric nutrients that are needed in tiny amounts in the diet and help to drive cell processes in the body. Vitamin precursors in foods are transformed into active vitamins by the body. The fat- soluble vitamins are vitamins A, D, E, and K; the water-soluble vitamins are vitamin C and the B vitamins. Vitamin A is essential to vision, integrity of epithelial tissue, bone growth, reproduction, and more. Vitamin A deficiency causes blindness, sickness, and death and is a major problem worldwide. Overdoses are possible and cause many serious symptoms. Foods are preferable to supplements for supplying vitamin A. The vitamin A precursor in plants, beta-carotene, is an effective antioxidant in the body. Brightly colored plant foods are richest in beta-carotene, and diets containing these foods are associated with good health. Vitamin D raises mineral levels in the blood, notably calcium and phosphorus, permitting bone formation and maintenance. A deficiency can cause rickets in childhood or osteomalacia in later life. Vitamin D is the most toxic of all the vitamins, and excesses are dangerous or deadly. People exposed to the sun make vitamin D from a cholesterol-like compound in their skin; fortified milk is an important food source. Vitamin E acts as an antioxidant in cell membranes and is especially important for the integrity of cells that are constantly exposed to high oxygen concentrations, namely, the lungs and red and white blood cells. Vitamin E deficiency is rare in human beings, but it does occur in newborn premature infants. The vitamin is widely distributed in plant foods; it is destroyed by high heat; toxicity is rare. Vitamin K is necessary for blood to clot; deficiency causes uncontrolled bleeding. The bacterial inhabitants of the digestive tract produce vitamin K. Toxicity causes jaundice. Vitamin C, an antioxidant, helps to maintain collagen, the protein of the connective tissue; protects against infection; and helps in iron absorption. The theory that vitamin C prevents or cures colds or cancer is not well supported by research. Taking high vitamin C doses may be unwise. Ample vitamin C can be easily obtained from foods. As part of coenzymes, the B vitamins help enzymes do their jobs. The B vitamins facilitate the work of every cell. Some help generate energy; others help make protein and new cells. B vitamins work everywhere in the body tissues to metabolize carbohydrate, fat, and protein. Historically, famous B vitamin deficiency diseases are beriberi (thiamin), pellagra (niacin), and pernicious anemia (vitamin B 12 ). Pellagra can be prevented by adequate protein because the amino acid tryptophan can be converted to niacin in the body. A high intake of folate can mask the blood symptom of vitamin B 12 deficiency but will not prevent the associated nerve damage. Vitamin B 6 is important in amino acid metabolism and can be toxic in excess. Biotin and pantothenic acid are important to the body and are
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