CH. 7 Key Concepts

Identify the roles of vitamin C, effects of its deficiency and toxicity, and its food sources.

Vitamin C maintains collagen, protects against infection, acts as an antioxidant, and aids iron absorption. Ample vitamin C can be easily obtained from foods.

Describe the collective roles of B vitamins in metabolism and the effects of their deficiencies.

As part of coenzymes, the B vitamins help enzymes in every cell do numerous jobs. B vitamins help metabolize carbohydrate, fat, and protein.

Describe how to choose foods to meet vitamin needs.

The eating pattern that best provides vitamin needs includes a wide variety of nutrient-dense foods that provide more than just isolated nutrients.

Describe the roles, food sources, and effects of deficiency and toxicity of vitamin E.

Vitamin E acts as an antioxidant in cell membranes. Average U.S. intakes fall short of DRI recommendations. Vitamin E-deficiency disease occurs rarely in newborn premature infants. Toxicity is rare, but supplements may carry risks.

Summarize the characteristics and functions of fat-soluble vitamins.

Because fat-soluble vitamins are stored, you need not eat foods containing each fat-soluble vitamin every day. Because of their ability to be stored, fat-soluble vitamins can become toxic if consumed in excess. Fat soluble vitamins play diverse roles in the body.

Describe the roles, the effects of deficiencies and toxicities, and food sources of each of the eight B vitamins. (Part 2)

High intakes can mask the blood symptom of a vitamin deficiency. Vitamin is critical for cell replication and proper nerve functioning. Vitamin occurs only in foods of animal origin. Vitamin -deficiency anemia mimics folate deficiency and arises with low intakes or, more often, poor absorption. Folate supplements can mask a vitamin deficiency. Vitamin works in amino acid metabolism. Biotin and pantothenic acid are parts of coenzymes import of lipids, hormones, and other vital cell components. Biotin and pantothenic acid are adequately supplied in a well-balanced diet. Choline is needed in the diet, but it is not a vitamin. Many U.S. adults do not consume the DRI amount of choline, but effects on health are uncertain. Many other substances that people claim are vitamins are not.

Describe the roles of vitamin D, its sources, and the consequences of its deficiency and toxicity.

Low and borderline blood vitamin D concentrations are not uncommon in the United States. When exposed to sunlight, the skin makes vitamin D; ultraviolet light from sunshine acts on a cholesterol compound in the skin to make vitamin D. Vitamin D helps regulate blood calcium and modifies genetic activities with far-reaching effects. A vitamin D deficiency causes rickets in childhood, low bone density in adolescence, and osteomalacia in later life. Vitamin D deficiency is likely in overweight people, those in northern climates, and those who lack sun exposure as well as in darker-skinned adults, adolescents, and breastfed infants. Vitamin D is the most potentially toxic vitamin. Overdoses raise blood calcium and damage soft tissues. The Dietary Reference Intake (DRI) for dietary vitamin D varies little through most of life. Food sources of vitamin D include a few naturally rich sources and many fortified foods.

Debate for and against taking vitamin supplements.

Most people can meet their nutrient needs from their diets alone; however, some people may need to take supplements (i.e., pregnant or lactating women, habitual dieters, strict vegetarians, etc.). Well-nourished people who also take supplements add excess nutrients to already sufficient intakes, which increases the risk for toxicity. Contamination of supplements, particularly those sold over the internet for weight loss or to enhance athletic or sexual performance, also pose as a risk.

Describe the roles, the effects of deficiencies and toxicities, and food sources of each of the eight B vitamins. (Part 1)

Thiamin is a coenzyme important in energy metabolism and in nerve cell processes. The thiamin deficiency disease is beriberi. Many foods supply small amounts of thiamin. Riboflavin's coenzyme is important in energy metabolism. Riboflavin is destroyed by ordinary light. Niacin forms coenzymes important in energy metabolism. Niacin deficiency causes the disease pellagra, which can be prevented by adequate niacin intake or adequate dietary protein. The amino acid tryptophan can be converted to niacin in the body. Folate is part of a coenzyme necessary for making new cells. Low intakes of folate cause anemia, digestive problems, and birth defects in infants of folate-deficient mothers.

Describe the roles, food sources, and precursor of vitamin A, and the effects of vitamin A deficiency and toxicity.

Three active forms of vitamin A and one precursor are important in nutrition. Vitamin A plays major roles in gene regulation, eyesight, reproduction, cell differentiation, immunity, and growth. Vitamin A deficiency causes blindness, sickness, and death and is a major problem worldwide. Vitamin A overdoses and toxicity cause many serious symptoms, such as blindness and birth defects. Vitamin A's active forms are supplied by foods of animal origin. The vitamin A precursor in plants, beta-carotene, is an effective antioxidant in the body. Many brightly colored plant foods are rich in beta-carotene.

Describe the roles of vitamin K, its food sources, and the effects of its deficiency and toxicity.

Vitamin K is necessary for blood to clot. Vitamin K deficiency causes uncontrolled bleeding. Excess vitamin K can cause harm. The bacterial inhabitants of the digestive tract produce vitamin K.

Compare fat-soluble vitamins with water-soluble vitamins.

Vitamins are essential, noncaloric nutrients that are needed in tiny amounts in the diet. They help to drive cellular processes. 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.

Summarize the characteristics of water-soluble vitamins.

Water-soluble vitamins are easily absorbed and excreted from the body, and foods that supply them must be consumed frequently. Water-soluble vitamins are easily lost or destroyed during food preparation and processing.