Many americans take vitamins or herbal preparations, believing they are contributing to a healthier lifestyle. That may not be true. In fact, time and research have shown that many of the benefits ascribed to certain supplements can not be proved, and some may even prove harmful.

The Food and Drug Administration defines a dietary supplement as anything taken orally that has ingredients such as vitamins, minerals, herbal or botanical components, amino acids, and substances such as enzymes, glandular or organ tissues or metabolites. Dietary supplements do not need the approval of the FDA to be marketed to the public, due to the Dietary Supplement Health & Education Act passed in 1994. Prior to that time, dietary supplements were under the same regulatory requirements as food. Under the DSHEA, dietary supplements do not go through the same rigorous testing and labeling processes as over-the-counter and prescription medications. Essentially, the government has little control over the purity, potency, safety or effectiveness of the supplements. As a result, some purveyors who choose to take advantage of the lack of legislation have been known to exaggerate or make false claims regarding various products.

Many people believe that if one eats a well-balanced diet, multivitamin supplements are unnecessary. For those who eat a lot of processed and fast foods, however, a daily multivitamin may not be a bad idea, especially for those trying to lose weight. Most such supplements provide 400 International Units of vitamin D, along with B vitamins. There’s no reason to believe that “high-potency” or “all-natural” vitamins are better than the rest.

Vitamins E, A, C and beta-carotene, favorite supplements in the ’80s and ’90s, were thought to protect against coronary artery disease. Research has since shown that vitamin E may increase the risk of respiratory diseases, moderate doses of vitamin A may increase the risk for fractures, and beta-carotene may increase the risk of lung cancers in men.

Important for women who are planning a pregnancy or who are pregnant, folic acid, a B vitamin, helps to prevent some birth defects. In very high doses niacin, another B vitamin, decreases cholesterol levels but also has side effects such as severe nausea, vomiting, diarrhea and liver damage. Even though niacin is sold over the counter, consult your physician before taking it.

With long work hours and the use of sun-blocking agents for preventing skin cancer, many of us have become deficient in vitamin D. Older individuals, those with chronic illnesses and people with dark complexions are more at risk of a deficiency because they absorb less ultraviolet energy from sunlight. Produced when skin is exposed to the sun, the vitamin helps the body absorb calcium and is important for healthy bones. Preliminary research also suggests it may reduce the risk of prostate and other cancers and some neuromuscular problems that cause falls. It can be difficult to get enough vitamin D from your diet. Look for vitamin D-fortified foods, such as dairy products, and include oily fish in your diet when possible. Taking vitamin D supplements makes good sense. Taking calcium supplements with vitamin D makes even better sense.

The mineral calcium strengthens and protects bones. Ideally, we should get it from the foods we eat, but most of us do not eat enough dairy products and calcium-rich or calcium-enriched foods. Calcium deficiencies can lead to osteoporosis in women. Supplements such as calcium carbonate and calcium citrate are the best sources of additional calcium because they are well absorbed. Some evidence suggests that very high levels of calcium increase the risk of cancer of the prostate. High levels may also increase the risk of kidney stones in men and women.

Chromium is not recommended for routine use. Heavily promoted for weight loss, this mineral has not been proven effective for that purpose. It may boost your good cholesterol (HDL) levels, but the evidence is mixed and needs further study.

Iron supplements are not recommended for healthy men. Healthy women should be fine with the amount of iron provided in their multivitamins. Iron supplements should be used only under the direction of your physician.

Research has found that 200 micrograms of selenium may reduce a man’s risk for prostate disease. More research needs to be done, but it is a reasonable supplement for men to take.

As always, when considering dietary supplements, talk with your doctor regarding the need and appropriate dosage. Read the literature regarding the evidence-based research done on the supplement to make an informed choice.

Avoid drug interactions with your prescription and OTC medications by reading all labels and discussing them with your pharmacist. Before surgery, tell your doctor about any supplements you take to avoid complications in the operating room. For more information, visit http://www.fda.gov