What Are Daily Values

Have you ever wondered what "% Daily Value" means on the Nutrition Facts label? How does it relate to the Dietary Reference Intakes (DRIs)? As you may recall from Chapter 1, the DRIs, set by the Food and Nutrition Board of the National Academy of Sciences, are the amounts of each nutrient recommended for most healthy people. Because DRIs are both sex- and age-specific, each nutrient has a range of DRIs. To make it easier to show how a food meets your recommended allowance for some of the more critical nutrients, the Food and Drug Administration has established a Daily Value for each nutrient, which is approximately the highest recommended amount for that nutrient. The "% Daily Value" reported on the Nutrition Facts label is based on a maintenance calorie level of 2,000 calories daily. If your maintenance calorie level is 1,500 calories, your daily values may be a bit lower, so the nutrient contents of the food satisfy a higher percentage of your daily value.

multivitamins or single-nutrient supplements to get your water-soluble vitamins, moderation is advised (see Supplement Sense, page 38), because high doses of several of the B vitamins can have harmful effects, and high doses of vitamin C may contribute to the formation of kidney stones.

Fat-Soluble Vitamins

The fat-soluble vitamins, A, D, E, and K, are found in the food you eat, absorbed into your bloodstream, and carried throughout your body attached to fat molecules. Because fat-soluble vitamins can be stored in the body, they do not need to be replenished on a daily basis. Vitamins A and D are stored in the liver, and reserve supplies may be sufficient for as long as 6 months. Reserves of vitamin K, however, may be sufficient for only a few weeks, and the supply of vitamin E can last somewhere between several days and several months.

If taken in excess, usually in the form of a supplement, fat-soluble vitamins can accumulate in the body. Large stores of vitamins A and D can actually become harmful. Fortunately, it is difficult to get an excess of fat-soluble vitamins from food. For example, beta-carotene, the molecule found in some foods of plant origin that gives carrots and squash their yellow-orange color, is converted to vitamin A in the body. But because the chemical reaction that converts beta-carotene to vitamin A is carefully regulated, it is nearly impossible to get vitamin A toxicity from eating fruits and vegetables. Foods that provide vitamins D, E, and K would need to be consumed in such quantity that achieving toxic levels of these nutrients is highly unlikely. However, a high intake of vitamin K-containing foods may contribute to abnormal bleeding in people who are receiving blood-thinning (anticoagulant) medication. Therefore, it is important to keep foods that are high in vitamin K relatively constant. Vitamin E supplements also are not recommended for these individuals.

The recent development of diet drugs that work by inhibiting your body's absorption of fat has raised concerns about the possibility that the use of such drugs could lead to deficiencies in the fat-soluble vitamins. Preliminary results suggest that when taken as directed, these drugs may interfere with the absorption of beta-carotene and vitamin D from foods. If these findings are confirmed, persons who take these prescribed drugs to manage their weight also will be required to take a daily multiple vitamin that contains the fat-soluble vitamin.

As mentioned in the discussion of fat substitutes, early research on the fat substitute olestra showed that eating olestra-containing snack foods interferes with the body's ability to absorb some of the fat-soluble vitamins from the other foods we eat. To compensate for this effect, the manufacturers of snack foods that contain olestra were required to fortify these products with fat-soluble vitamins. Thus, eating olestra-containing snack foods does not seem to create a significant risk for deficiency of fat-soluble vitamins (unless you consistently choose to eat them in place of more nutritious foods).

To learn about the many roles of vitamins, how much of each of them you need, and the best food sources for each one, see the Appendix: A Quick Look—Vitamins, Their Functions and Food Sources, page 430.

Minerals

Minerals are just what the term indicates—elements found in the earth. Like the vitamins, minerals play a multitude of roles in our bodies. Unlike the vitamins, some minerals— calcium and phosphorus—have a structural function. These minerals are the main components of our bones and teeth. Calcium has an additional critical role. Along with several other major minerals—sodium, chlorine, potassium, and magnesium—calcium is a regulator of cell function. The minerals sodium, chloride, and potassium (also referred to as electrolytes) are responsible for maintaining the balance of fluids inside and outside of cells and, along with calcium, controlling the movement of nerve impulses.

Trace minerals are those that your body needs in smaller amounts, usually less than 20 milligrams daily. These include iron, chromium, cobalt, copper, fluoride, iodine, manganese, molybdenum, selenium, and zinc. The mineral iron forms the active part of hemoglobin, the protein in your blood that delivers oxygen to different sites in your body and picks up carbon dioxide. Although DRIs have been established for some of the trace minerals, those for which too little is known to establish precise DRIs have a recommended Adequate Intake (AI) (see the Appendix: A Quick Look—Minerals, Their Functions and Food Sources, page 432).

Vitamins and Minerals as Antioxidants

Several vitamins and minerals are considered antioxidants. These include vitamins E and C, beta-carotene (which can be converted to vitamin A), other carotenoids (some may be converted to vitamin A and also play a role in cell devel opment), and the minerals selenium, copper, zinc, and manganese. What are antioxidants? What do they do?

Every cell in our body needs oxygen to use the nutrients that food provides. However, when oxygen is used by cells, by-products called free radicals are formed. If allowed to accumulate, these free radicals can damage tissues, cells, and deoxyribonucleic acid (DNA, the genetic material of cells). The process of oxidative damage can be observed as the browning that occurs when sliced apples or potatoes are exposed to the air or the rancid flavor that butter and cooking oils develop when stored for long periods. Environmental pollutants such as cigarette smoke and ultraviolet light from the sun also contribute to the formation of free radicals in our bodies. Although not proved, studies suggest that excess free-radical production can increase the risk of cancer, heart disease, cataracts, and the other types of cell deterioration that are associated with aging.

Just as the vitamin C in lemon juice can prevent sliced apples from browning, antioxidants scavenge and neutralize the effects of free radicals in our bodies. Each antioxidant has its own unique effect. Vitamin C, which is water-

100 Weight Loss Tips

100 Weight Loss Tips

Make a plan If you want to lose weight, you need to make a plan for it. Planning involves setting your goals both short term and long term ones. With proper planning, you would be able to have an effective guide on the steps that you want to take, towards losing pounds of weight. Aside from that, it would also keep you motivated.

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