Campus Life

The Medical Minute: Vitamin supplements - need or notion?

By John Messmer
Penn State Family & Community Medicine
Penn State Milton S. Hershey Medical Center
Penn State College of Medicine

Vitamin supplements line the shelves in the drug store, food store, wholesale club and nutrition center and are the products of a multibillion-dollar industry. Today's vitamin ads tout energy, stress-relief and anti-aging benefits. Clearly there's a market for them -- about half of all Americans take vitamin or mineral supplements according to the British medical journal, Lancet -- but are they necessary?

Vitamin-sellers might argue that Americans eat the wrong foods and cannot properly process the foods eaten without the correct vitamins. They also claim that commercial food preparation and handling destroys food's natural vitamins so supplements are necessary. Beyond nutrition, people are trying to slow aging and reduce the risk of heart disease and cancer through supplementation.

For the most part, vitamins assist in various chemical reactions involved in building tissues and helping them function properly. They are not a substitute for the protein, fats and carbohydrates in food. Deficiencies can result in structural deficits, organ malfunction and metabolic derangement, depending on the vitamin. The opposite is not true, however. Just because something works poorly with a vitamin deficiency, taking a lot will not make it work much better than normal. In fact, taking too much of some vitamins can damage organs and cause death.

There are two large classes of vitamins: water-soluble and fat-soluble. Water-soluble vitamins include the B vitamins and vitamin C. Fat-soluble vitamins are A, D, E and K.

The B vitamins are thiamine (B-1), riboflavin (B-2), niacin (B-3), pantothenic acid (B-5), pyridoxine (B-6), biotin (B-7, but some do not classify biotin as a true vitamin), folic acid and cobalamin (B-12). These vitamins come from many dietary sources -- the B vitamins from whole and enriched grains and grain products, legumes, dairy and eggs, some vegetables, many meats, seafood and yeast. All fruits and vegetables contain vitamin C, not just citrus fruits. For the most part, B vitamins are needed to process food into energy and to maintain the structure of muscles, nerves, blood, skin and hair. Vitamin C helps body structural repair and neutralizes toxic byproducts of metabolism.

The body can store about five years' worth of vitamin B-12 and about six months' need of folic acid. A little niacin can be made from tryptophan. Since individuals can neither store nor make the others, the rest of the water-soluble vitamins are needed daily from foods. Any not used are eliminated in urine.

Fat-soluble vitamins are stored to some degree and the body makes some. Vitamin A is stored in the liver and is synthesized from beta carotene found in many colored fruits and vegetables. Vitamin D is found in fish, oysters and milk, although vitamins A and D are usually added to milk in processing. However, individuals can make their own vitamin D with 10 minutes of exposure to the sun three times a week in most parts of the world. Vitamin E comes from nuts, seeds, vegetable oils and dark green vegetables, and can be synthesized from tocopherol which also is found in these foods. Vitamin K sources are green leafy vegetables, cabbage and soybeans, and normal bacteria in the intestines produce it.

Minerals are elements, or single atoms, rather than complex molecules. Iron carries oxygen in red blood cells and helps in energy metabolism and nerve function. Calcium provides the structural strength in bones and teeth but also is part of muscle and nerve function and blood clotting. Other needed minerals include iodine for the thyroid; magnesium for muscle and nerve function; phosphorus for bones and calcium regulation; zinc for structural integrity and certain metabolic activities; selenium for immune function and to protect from free radicals; copper for healing and handling other minerals; chromium and manganese for carbohydrate metabolism; and molybdenum as an enzyme cofactor. Sodium, potassium and chloride are involved everywhere in the body from nerve and muscle function to water balance. These elements are regulated by the kidney and are not typically supplemented in healthy people.

Most minerals are readily available from foods, either naturally or through fortification, so supplementation usually is not needed. The exceptions are calcium and iron, but the proper amount varies by age, gender and health status.

So, who should take supplements and which ones should be taken? The average healthy person should eat a variety of foods from various groups. In a typical week, if eating several types of fruits and vegetables, some nuts and seeds, whole grains, some lean meat and fish or at least eggs and dairy products, and getting outside for 10 minutes three times a week, no extra vitamins are needed. Most who fit this description do not need any minerals, either, but there are exceptions.

About 1,600 balanced calories a day need to be consumed to get the variety needed for the recommended daily allowance of vitamins. If an individual is sedentary, elderly or very thin, he or she might not eat enough total food to obtain enough vitamins, so a simple multivitamin might be appropriate. Illness may increase the need for certain vitamins and minerals.

Women who might conceive may not be able to consume enough food without gaining weight to ensure sufficient folic acid, so a supplement is recommended. Similarly, women in their childbearing years may lose more iron through menstruation than they consume, so a small iron supplement usually is appropriate, and more during pregnancy and nursing.

Children's need for iron supplementation should be decided on a case-by-case basis by their doctors. Most men do not need any extra iron. Some families carry a gene for hemachromatosis which allows them to store iron even if it is not needed. Too much iron is toxic to the liver, heart and nervous system.

Women lose calcium from their bones starting in their mid-30s and more rapidly after menopause. To build strong bones, most doctors recommend calcium supplements for adolescents and adults who do not consume enough dairy and for most women after menopause to reduce the risk of osteoporosis.

Research to date has not proven any benefit to routine vitamin supplementation outside of specific situations. Vitamin E supplements have not demonstrated any advantage in research and extra beta carotene has been shown to be harmful. Vegetarians might benefit from one or more supplements, but recommendations vary according to what foods are excluded from the diet.

Vitamins cannot counteract unhealthy habits. The best thing for good health is to not smoke, exercise regularly, eat a variety of foods and maintain a normal weight. Unneeded supplements literally flush money down the toilet.

Last Updated March 19, 2009

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