More than 100 million Americans take dietary supplements daily.

No one disputes the health benefits of diets rich in fruits, vegetables, and whole grains. Scientists are working to identify the exact components in these diets that confer protection against chronic diseases such as heart disease and cancer.

Currently, universities, industry, non-government organizations, and government are collaborating on clinical trials to demonstrate the effectiveness of functional foods.
Many vitamins and minerals are not absorbed well and, as a result, are not retained by the body. 

Some appetite suppressants can create psychological dependence because they contain phentermine, which is chemically similar to amphetamines. Others can cause insomnia, drowsiness, irritability, or depression.

Synthetic vitamins are usually the same as natural vitamins, but natural vitamins usually cost more.

Like prescription medicines, supplements should be kept out of reach of children in a dry, cool place. Avoid hot, humid storage locations, such as the bathroom.

Vitamin E and beta-carotene supplements do not have preventive effects on stroke in middle-aged men who smoke, Finnish and US researchers report. The findings come from further analysis of data from the Alpha Tocopherol, Beta Carotene Cancer Prevention Study, a trial involving more than 29,000 male smokers between 50 and 69 years. It was originally intended to see if these antioxidants cut the risk of lung cancer.
Despite some reports that antioxidant vitamins have cardiovascular benefits, a panel of experts at the American Heart Association (AHA) has concluded that there is too little evidence to recommend taking antioxidant supplements to reduce the risk of heart disease. Instead, the AHA panel advises you to get plenty of antioxidants from food sources such as fruits, vegetables, whole grains, and nuts.

Some people take amino acid (the building blocks of protein) powders to increase muscle. Research shows that eating more protein or more amino acids does not lead to increased muscle building. Exercise determines muscle building.

According to the 2002 edition of the National Center for Health Statistic's National Health Interview Survey, Americans are most likely to use Complementary and Alternative Medicine (CAM) for back, neck, head, or joint aches, or other painful conditions; colds; anxiety or depression; gastrointestinal disorders; or sleeping problems. CAM is most often used to treat and/or prevent musculoskeletal conditions or other conditions involving chronic or recurring pain.