The Vitamin ABC's

Vitamins are essential to life. Without them, the trillions of chemical reactions within our bodies would bog down or fail entirely, leaving us vulnerable to a host of diseases in our increasingly toxic world.

The first vitamin was discovered in the late 19th century as scientists began to study foods that were well-known for preventing certain diseases (like oranges and scurvy). Many of the other vitamins were discovered in 1930s and 1940s. Most vitamins work as catalysts that speed up chemical reactions in the body. Sixty years later scientists are still learning more about these amazing micronutrients.

"As co-enzymes," writes Dr. James F. Balch in Prescription for Nutritional Healing, "vitamins work with enzymes, thereby allowing all the activities that occur within the body to be carried out as they should." Vitamins are considered to be micronutrients because we only need relatively small amounts of them to maintain basic health.

Essential to health

Everything our bodies do, from digesting food to fighting invading viruses, depends on vitamins. With the exception of a few B vitamins, the human body does not manufacture vitamins. They must be obtained from outside sources. This makes the food we eat that much more critical to our good health.

Water-soluble vitamins (C and B-complex) cannot be stored in the body; excess amounts are flushed from the body via urine. Fat- or oil-soluble vitamins (A, D, E, and K), are stored in the fatty tissues for future use. Because they accumulate in organs like the liver, megadoses of these over long periods of time can lead to toxicity. Megadosing is becoming more popular as a therapeutic measure but can be dangerous and should be guided by your healthcare provider.

The federal government has established basic guidelines for vitamin and mineral intake. Called the Recommended Dietary Allowance (RDA), the amounts vary according to factors such as age, weight, and sex. The National Academy of Sciences also publishes Dietary Reference Intake (DRI) values; the Food and Drug Administration also uses its Daily Value (DV). These values need to be modified for specific situation, such as being a senior citizen, eating a vegetarian diet, recovering from surgery, being pregnant, or having a health condition such as alcoholism.

It is important to become the best expert that you know. Analyze the vitamin content of your diet to determine which supplements you need to take. Develop a vitamin strategy for when illness strikes or if you have specific health concerns. Most experts agree that natural vitamins are better than synthetic ones. And stay informed--study the latest findings in medical journals and health magazines.

Vitamin A/Beta-Carotene

Because vitamin A was the first to be discovered, it was named simply "A." This fat- or lipid-soluble nutrient is associated with oils in food; vitamin A works best when it is taken with fat-containing foods, which stimulate the digestive system to break down and utilize vitamin A.

Vitamin A (also known as retinol) is critical to many biochemical reactions, including those involving the retina, cell growth, skin regeneration, and the immune system. Protein cannot be utilized without vitamin A. One of the earliest observed benefits of vitamin A was how it improved night vision. In fact, vitamin A deficiency is one of the leading causes of blindness in children in developing countries.

Small amounts of vitamin E help the body store vitamin A for future use (amounts exceeding 600 IU [international units, however, can interfere with the absorption of beta carotene). Vitamin A needs proper levels of zinc, vitamins C, D, and E, and choline to be effective.

Carotenoids are compounds that are structurally similar to vitamin A. Beta-carotene, which is actually a double vitamin A molecule, is the most well-known carotenoid and converted by the liver into vitamin A. Because beta-carotene is water-soluble, the body eliminates excess amounts, which means beta-carotene does not have the toxic potential that vitamin A does.

Both vitamin A and beta-carotene are powerful antioxidants that neutralize free radicals--molecules that scavenge electrons from healthy cells, creating abnormalities that can lead to diseases like cancer. If you smoke or are exposed frequently to sunlight, vitamin A/beta-carotene may be an important supplement to add to your diet.

Other conditions vitamin A can help are depressed immune system function, infertility, weak tissues and bones, viral infections like measles, acne, psoriasis, and other skin conditions, and the side effects from radiation and chemotherapy. Because vitamin A protects the skin and keeps it supple, strengthens muscle and bone, and fights cancer, it also reduces the effects of aging.

Food sources: Vitamin A is found in animal fats such as egg yolks. Beta-carotene is enriched in orange and yellow fruits (carrots, yams) and vegetables such as spinach and parsley.

Dosage: The DV for vitamin A is 5,000 IU (the RDA varies according to age, sex, and state of health). Toxic amounts can result in vomiting, brain disorders, swelling of the liver, and birth defects in fetuses. Deficiencies may weaken the digestive and respiratory tracts, making them more susceptible to infection. Children, adults with liver problems or hypothyroidism, and pregnant women should be careful about taking too much vitamin A. Safe amounts of beta-carotene are considered to be between 10,000 and 50,000 IU.