The supplements in question contain bitter orange, an herb used for thousands of years.

But now, there is some question of safety over this herbal remedy.

"It's not quite speed, but it is something (that) can speed up the heart, which is the synephrine component," said Scripps Cardiologist Dr. Mimi Guarneri.

Bitter orange is found in everything from orange marmalade to weight loss and energy supplements.

Bitter orange herb contains synephrine -- a compound that is chemically similar to ephedrine, the active compound in ephedra.

"We did live through ephedra -- it was very scary, we saw (a) major stroke, heart attack (and) high blood pressure," said Guarneri.

Since the Food and Drug Administration banned ephedra containing supplements, the popularity of bitter orange has skyrocketed.

"The real question here is there evidence that bitter orange is going to cause someone a heart attack, a stroke or worsen their blood pressure?" said Guarneri.

Researchers from the University of California San Francisco studied several different supplements containing bitter orange and caffeine.

The small study showed some combinations raised blood pressure and heart rates in healthy adult study participants after a single dose.

"That doesn't translate necessarily into somebody having a stroke or heart attack," said Guarneri.

But it does mean consumers should be aware of possible health risks when bitter orange is combined with other stimulants.

"Just because they come from a natural place doesn't mean they don't have side effects. (It) doesn't mean they may not interact with prescription medication, so whenever you are taking something because you think (could) be a benefit, find out what the potential downside is," said Guarneri.

Many people take supplements with bitter orange to lose weight, but medical research shows there is little evidence to show it really works.