Newswise — If you're curious about the dizzying array of nutritional supplements available, you're not alone. Annual sales in the category top $4 billion.

Eating a healthy diet will typically supply sufficient nutrients, but if you decide to try a product, consult with your doctor and pharmacist. Supplements can be overkill if you're already taking a multivitamin. They also can cause allergic reactions and interact with medications.

"Most people think that if they get a substance over the counter, it's all right to take," notes Rudy Nelson Lea Jr., M.D., a family medicine physician on the medical staff at Baylor Medical Center at Garland. "But if you're taking prescription medicine at the same time, it's often not all right."

Following are some of the most common supplements and their benefits and potential dangers.

CalciumProposed benefit: Osteoporosis preventionBeware: Most calcium supplements should be taken with food but some are absorbed differently and may be taken on an empty stomach. If in doubt, check the label or ask your health care provider, advises Julie A. Allen, Pharm.D., R.Ph., pharmacy director at Baylor Garland.

EchinaceaProposed benefit: Treatment of respiratory infections such as the common cold. "Proponents suggest that it increases the response of white blood cells—the cells in the body that fight off infections," Dr. Lea says.Beware: People who are on medication that suppresses the immune system should avoid echinacea.

IronProposed benefit: Treatment of low blood iron or anemia by helping the body make red blood cells.Beware: Iron may affect the results of certain medical tests. Possible side effects include bloody diarrhea, constipation and fever.

Omega-3 fatty acids Proposed benefit: Enhanced cardiovascular health, brain function and immunity. For patients with elevated triglycerides, Dr. Lea recommends one gram in the form of fish oil capsules with each meal.Beware: A high intake could cause excessive bleeding—supplementing should be stopped two weeks before and after surgery.

Vitamin B complexProposed benefit: Reduction in heart disease and stroke risk due to a reduction in levels of homocysteine, an amino acid linked to heart disease. Beware: Possible side effects include nausea, diarrhea and gas.

For more information about Baylor Medical Center at Garland, visit http://www.BaylorHealth.com.