Columbia, S.C. Consumers can be confused by the loads of often conflicting information that exists about dietary supplements such as vitamins, minerals and herbals.
In addition, dietitians warn that products labeled "natural" are not necessarily healthful or safe; and extraordinary claims by product manufacturers might be false.
"If it sounds too good to be true, it probably is," said Teresa Moore, an associate professor in the exercise science department of USC's Arnold School of Public Health.
While supplements can be helpful, you should consult with a registered dietitian or health care provider before taking them.
And be aware that supplements won't replace everything missing from an unbalanced diet, Moore said.
"It always comes back to a very good, healthy diet," she said.
Moore is not against taking general vitamin supplements, but advises - against "mega" doses because taking too much of some nutrients can cause trouble.
Some substances can cause harmful effects when used with prescription and over the counter medicines or can reduce the effectiveness of prescription drugs.
Here's information about some common supplements:
Calcium, a chemical element, plays a vital role in blood clotting, muscle contraction, nerve transmission and the formation of bones and teeth. It is important for fighting osteoporosis, a condition that weakens bones and increases the risk of fractures. Osteoporosis occurs more often in women than men, but age, race and body type are also factors.
Food sources: Calcium is found in dairy products such as milk and cheese; and vegetables such as broccoli, kale and Chinese cabbage.
Did you know? Vitamin D helps with calcium absorption in the body.
Also known as folic acid and Folacin, folate is known to prevent defects of the neural tube - the part of an embryo that develops into the brain and spinal cord.
Women should take folic acid supplements or fortified foods in addition to dietary folate before they become pregnant.
Food sources: Folate can be found in whole grains and whole grain cereals - breads, dried beans as well as dark, leafy vegetables.
Did you know? Folate cannot reverse neural tube damage.
A powerful antioxidant found in tomatoes, lycopene is thought to help protect against prostate and breast cancers.
A 2003 study by researchers at Ohio State University, showed that pure lycopene was less effective against prostate cancer than tomato products that naturally contain lycopene. The authors said these results suggest that lycopene may be a substance that works best with other compounds with which it naturally occurs.
Food sources: The study suggests that tomato products may be more effective than lycopene supplements.
Did you know? Lycopene and other dietary supplements are not regulated by the Food and Drug Administration.