Thanks to the efforts and authority of the Food and Drug Administration, prescription drugs sold in the United States tend to be relatively safe. Any side effects or risks that the drugs do have must be disclosed.

That being said, it is a mistake to assume that anything sold as a non-prescription “dietary supplement” is safe simply because it is on store shelves. The FDA’s regulatory authority over prescription drugs makes it reasonably easy to issue recalls on dangerous and defective drugs. But the agency has far less authority over dietary supplements, which means consumers may have no way of knowing whether a given product is effective or safe.

Consumer advocacy groups note that most dietary supplements containing simply vitamins and minerals are safe and probably labeled accurately; particularly products sold as single ingredients (calcium or vitamin D, for example).

But as soon a dietary supplement starts promising weight loss, bigger muscles or better sexual performance, consumers should be very skeptical. There are more than 400 supplement brands that the FDA has identified as being tainted with pharmaceuticals.

This means that they may contain a drug which should be sold under prescription only. More often, however, these supplements contain pharmaceutical drugs which are illegal in the United States because they have not been approved or have been deemed dangerous to health.

Of the 400 supplements identified by the FDA, approximately 70 percent have been recalled. Unfortunately, it is very difficult to get these supplements completely off the market, and some remain available for months or even years after being recalled. Others are simply repackaged and sold under a different brand or product name.

Before taking any dietary supplements, it pays to do some research. Where are the supplements manufactured? Does the manufacturer seem reputable? Could you contact the company if you wanted or need to?

Most importantly, you should be skeptical of the promises these products make. Remember: If something sounds too good to be true, it probably is.

Source: Reuters, “Recalled, drug-tainted supplements still available for purchase,” Kathryn Doyle, Oct. 21, 2014