Vitamins and Minerals

Vitamins and minerals are required by every process in your body. Unlike the macronutrients, vitamins and minerals by themselves do not contain energy. Instead, they work with the energy-rich macronutrients—carbohydrates, protein, and fats—and with each other to help your body to release, use, and store the energy from those macronutrients.

Vitamins

Vitamins are small but complex molecules. In addition to helping us to use and store energy from macronutrients, they assist the molecules responsible for vision to perform their function, they serve as regulatory hormones for bone formation, and they act as antioxidants to preserve cellular function (see Vitamins and Minerals as Antioxidants, page 31).

Each of the vitamins was discovered and its requirement determined by its ability to cure and prevent a particular disease or group of symptoms. For example, the discovery that a substance in limes could cure and prevent the disease called scurvy led to the discovery that our bodies require vitamin C and that scurvy is the result of vitamin C deficiency. Dietary Reference Intakes (DRIs) are being established for each vitamin. They describe the amount of the vitamin that should prevent symptoms of deficiency in most people, with a little extra added.

Today, the diseases that result from vitamin deficiencies rarely occur except in severely malnourished individuals or in those with certain medical conditions. Rather, in a virtual nutrition revolution, research has progressed beyond the identification and treatment of simple nutrient deficiencies to the realization that some of the vitamins (or foods that contain them) may help maintain health by preventing the development of chronic diseases such as cancer and heart disease in otherwise well-nourished people.

The Food Guide Pyramid is based on the DRIs. It tells us the number of servings, in each group of foods, that will supply us with the recommended allowance of most of the vitamins. Nutrition research also has begun to support the idea that a few of the vitamins and minerals, notably those referred to as antioxidants (see Vitamins and Minerals as Antioxidants, page 31), may provide even more benefit if taken in quantities somewhat greater than the recommended amounts. This idea raises some questions. Is there such a thing as too much of a vitamin? Should these extra vitamins come from food, or is it okay to take a supplement if you just can't eat that much? And, should the recommended amounts for these vitamins be increased? Although there really is no answer to the last question yet, the answers to the first two questions depend on the type of vitamin. As we begin our discussion of vitamins, we want to emphasize that although it is virtually impossible to overdose on vitamins from food alone, some vitamin supplements definitely offer too much of a good thing (see sidebar: What Are Daily Values? this page, and Supplement Sense, page 38).

The 14 essential vitamins can be classified into two groups: water-soluble and fat-soluble. They are classified on the basis of their molecular structure, which determines the way the vitamins are carried in food and in the bloodstream and the manner in which they are stored in your body. The text that follows describes which vitamins fall into which category and what that means for your health.

Water-Soluble Vitamins

There are 10 water-soluble vitamins. The B complex vitamins have various roles, some of which involve their action, in concert, to regulate the body's use of energy from food. Folic acid is an important factor in the regulation of growth. During the early stages of pregnancy, folic acid is important for preventing a type of birth defect known as a neural tube defect. Vitamin C, also known as ascorbic acid, functions in various ways, many of which seem to be related to its antioxidant properties (see the Appendix: A Quick Look— Vitamins, Their Functions and Food Sources, page 430).

As their name implies, water-soluble vitamins dissolve in water. The body strives to maintain the optimal level of each of the water-soluble vitamins for its immediate needs. Surplus water-soluble vitamins are excreted in the urine and through perspiration, because they are not stored in the body to any appreciable extent. Water-soluble vitamins must be replenished almost daily, preferably by eating foods that are rich in these vitamins. Fruits, vegetables, grains, and beans are excellent sources of the water-soluble vitamins (with the exception of vitamin B^, which is found only in foods of animal origin). However, if you choose to use

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