One study, completed in 2000, tested a group of subjects in order to see the effects of tribulus terrestris supplements on people's resistance-training abilities. The study found that at the end of the trial, the subjects did not improve their body composition or their resistance-training performance [source: Antonio et al].
Tribulus Terrestris Side Effects
The United States Food and Drug Administration (FDA) does not regulate tribulus terrestris so be aware that tribulus terrestris has not been scrutinized the way many other medications and drug treatments have. Therefore, the full spectrum of possible side effects is unknown at this time.
Considering this limitation, the information available to you as a consumer that deals with the side effects of tribulus terrestris is incomplete. Some sites even claim that there are not even any known side effects of tribulus terrestris [sources: Santoso, Monson and Schoenstadt].
One potential negative side effect includes increased levels of testosterone, since tribulus terrestris is said to boost this hormone. Testosterone might have an effect on rage, hair growth and prostate size [source: Monson and Schoenstadt].
Another could come from how you decide to ingest tribulus terrestris. If you plan to take it, you should opt for a supplement instead of trying to consume any portion of the actual spiny plant -- one man punctured his lungs after doing so.
It's important to keep in mind that the various tribulus terrestris extracts available in health stores are not all created equal (remember, there is no regulation of supplements by the FDA). One writer recommends that you find the supplement with at least 45 percent protodioscin, which is the active ingredient [source: Santoso]. Different supplements will contain different percentages of ingredients, so be sure to read the ingredients label on the bottle. Compare the labels of different brands to determine which one might work best for you. Remember to consider any medications you are currently taking that could possibly react with the other ingredients found in the tribulus terrestris supplement. And it's a good idea to speak with your doctor before adding anything new to your daily regimen.
Looking for speed, size and strength? Read the next page to see how sports athletes use tribulus terrestris.