Dieters looking for a safer alternative to ephedra-based diet pills might be out of luck. New research shows that two popular supplements promoted as safe and ephedra-free can also raise heart rate and blood pressure in healthy people.

“One [formula] increased blood pressure as much as ephedra-containing supplements ... so they may carry similar health risks,” says Neal Benowitz, a clinical pharmacologist at UC San Francisco who participated in the study. The Food and Drug Administration banned ephedra in 2004 after it was linked to Heart Attacks, Strokes and death.

Benowitz and lead scientist Christine Haller, also at UC San Francisco, studied two diet supplements - Advantra Z and Xenadrine EFX - containing bitter orange. This extract’s active component, called synephrine, is used in its pharmaceutical form to treat low blood pressure.

Researchers compared heart rate and blood pressure in 10 healthy volunteers for several hours after they took the supplements and a placebo. They found that both supplements raised heart rate by 11 to 16 beats per minute over baseline. Xenadrine EFX, which also contains caffeine, raised blood pressure by 7% to 12%.

“The increase in heart rate and blood pressure together is of most concern,” says Benowitz. “If you have a history of cardiovascular disease or High Blood Pressure, you should be very cautious.”

The research was published in the September issue of the American Journal of Medicine.