Tribulus terrestris (commonly known as puncture vine—the bane of bicycles in areas where it grows) has a long history of traditional medical use in China, India, and Greece. It was recommended as a treatment for female infertility, impotence, and low libido in both men and women, and to aid rejuvenation after long illness. The herb became widely known in the West when medal-winning Bulgarian Olympic athletes claimed that use of tribulus had contributed to their success. However, current evidence suggests that it does not enhance sports performance.

Studies performed in Bulgaria are the primary source of most current health claims regarding tribulus. According to this research, tribulus increases levels of various hormones in the steroid family, including testosterone, DHEA, and estrogen, and for this reason improves sports performance, fertility in men and women, sexual function (again inmen and women), and symptoms of menopause(such as hot flashes).7-11Unfortunately, the design of these studies appears to fall far short of modern scientific standards, and there has not been any trustworthy scientific confirmation of these supposed benefits. One well-designed study failed to find that tribulus affects male sex hormone levels in young men.17

Other studies that are far too preliminary to prove anything at all are quoted as proving that tribulus is helpful for the treatment of angina, high cholesterol, diabetes, and muscle spasms, and for the prevention ofkidney stones.1,13-16

A properly designed, though small, human study compared the effects of tribulus (3.21 mg per kilogram of body weight—for example, 292 mg daily for a 200-lb man) against placeboon body composition and endurance among 15 men engaged in resistance training.3 At the end of the 8-week study, the only significant difference between the treatment and placebo groups was that the placebo group showed greater gains in endurance!

Another double-blind, placebo-controlled study enrolled 22 athletes and followed them for five weeks.18 The dose used in this trial was fixed at 450 mg daily for all participants. No benefits were seen.