THE MICRONUTRIENTS

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 functions.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.

 

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, 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.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

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.

 

WHAT ARE DAILY VALUES?

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.

 

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.

 

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).

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 development), 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 nutrientsthat 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.