Vitamins - From A to Zinc

What Are Vitamins?

Vitamins are organic compounds that occur naturally in plant and animal tissues. They are necessary in very small amounts in the diet to promote growth and maintain health and life. Essentially, vitamins make it possible for other nutrients to be digested, absorbed, and metabolized by the body. It is important to remember that since vitamins do not contain calories, they provide no energy. Vitamins act as catalysts—they increase the speed of chemical reactions without being used up by the reaction. This explains why vitamins are only needed in miniscule amounts.

Are There Different Types of Vitamins?

Vitamins can be divided into two groups—fat soluble (A, D, E and K) and water soluble (C and the B complex).The concentration of water soluble vitamins is regulated by the kidneys. Any intake in excess of the body’s need is excreted in the urine.Fat soluble vitamins, however, are stored in the body, and excessive intakes (especially of vitamins A and D) can lead to toxicity. Some water soluble vitamins and most minerals can also be toxic in large amounts.

How Do I Know If I Am Meeting My Vitamin Needs?

The best way to ensure you are receiving all the nutrients your body needs is to eat a well-balanced diet. The Recommended Dietary Allowances (RDAs) indicate the level of nutrients that will meet the needs of most healthy individuals. Because of an added safety factor, the RDAs are actually set higher than the level most people need. If your diet consists of a variety of foods from all the food groups, it is virtually impossible for you to develop a vitamin deficiency. In addition, many food products (like cereals, juices, and sports bars) are now fortified with many vitamins and minerals, making it easier than ever to meet our needs with foods alone.

What About Vitamin Supplements?

Since vitamins are only needed in tiny amounts, most healthy people can meet their needs through balanced, wholesome food choices. Situations in which a supplement may be recommended include pregnant women, elderly, strict vegetarians, people with multiple food allergies or intolerances, habitual dieters, and busy students with poor eating habits.

If you are going to take a supplement, select a multivitamin and multi-mineral that provides all nutrients below or at the RDAs. Prolonged intake of some vitamins in excess of the RDA can produce toxic effects, which may include: nausea, vomiting, skin disorders, liver and nerve damage, and even death. Remember, taking vitamin supplements won’t fix a poor diet. They can’t neutralize the damaging effects of excess saturated fat, salt, and sugar. Nor do they supply the disease-fighting phytochemicals found only in fruits, vegetables, and whole grains.

Vitamins, Stress, and Energy

Many claims exist regarding the need for vitamin supplementation. While your need for vitamins during times of stress may increase slightly, this need almost never exceeds the RDAs. Also, vitamins do not provide energy and will not help improve athletic performance. An athlete generally consumes more food and therefore receives more vitamins. The vitamins do not increase stamina or endurance, though, since they do not provide calories. Finally, if you are feeling tired or listless, you may need to sleep more, eat better, and be more physically active—taking a vitamin supplement is probably not the answer.

Does Vitamin C Prevent the Common Cold?

Research findings do not support the theory that vitamin C prevents the common cold. High doses, however, may have an antihistamine effect and thus relieve some of a cold’s symptoms. It’s important to keep in mind that mega-doses of vitamin C (>2000 mg/day) may be hazardous. And, it’s easy to get plenty from foods alone. Just six to eight ounces of orange juice provides the RDA for vitamin C.

Know Your Vitamins and Minerals

These charts highlight some basic vitamins and minerals, their sources and functions, and the Recommended Dietary Allowances (RDA) or Adequate Intakes (AI).   Remember that just because a vitamin or mineral performs a specific function, it does not mean that more is better. Supplements providing more than the Upper Limit (UL) listed below may actually have toxic effects.

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