When you reach for that bottle of vitamin C or fish oil pills, you may wonder how effective they are and whether they are safe. The first thing to ask yourself is whether you need them in the first place.

More than half of Americans take one or more dietary supplements daily or occasionally. Vitamin and supplements are available without a prescription and usually come in pill, powder, or liquid form. Common supplements include vitamins, minerals, and herbal products, also known as botanicals.

People take these supplements to ensure they get enough essential nutrients and to maintain or improve their health. But not everyone needs to take supplements.

"You can get all the nutrients you need by eating a variety of healthy foods, so you don't have to eat just one," says Carol Haggans, a registered dietitian and consultant at the National Institutes of Health. . "However, supplements can be used to fill gaps in your diet."

Some supplements can have side effects, especially if taken before surgery or with other medications. Supplements can also cause problems if you have certain health conditions. The effects of many supplements have not been tested in children, pregnant women and other groups. Therefore, if you are considering taking dietary supplements, consult your health care provider.

"You should talk to your doctor about what supplements you are taking so your care can be integrated and managed," advises Dr. Craig Hopp, a plant research specialist at the National Institutes of Health. .

The U.S. Food and Drug Administration (FDA) regulates dietary supplements as foods rather than drugs. The label may claim certain health benefits. But unlike drugs, supplements can't claim to cure, treat, or prevent disease.

"There is little evidence that any supplement reverses the course of any chronic disease," Hope said. . "Don't take supplements with that expectation."