What is Tribulus?Tribulus terrestris, also known as puncture vine, is a herb that has been used in the traditional medicine of China and India for centuries.
In the mid-1990s, tribulus terrestris became known in North America after Eastern European Olympic athletes said that taking tribulus helped their performance.
The active compounds in tribulus are called steroidal saponins. Two types, called furostanol glycosides and spirostanol glycosides, appear to be involved with the effects of tribulus. These saponins are found primarily in the leaf.
Why Do People Use Tribulus?Tribulus is most often used for infertility, erectile dysfunction, and low libido. In the last decade, it has become popular to improve sports performance.
Tribulus has been marketed these conditions because research performed in Bulgaria and Russia indicates that tribulus increases levels of the hormones testosterone (by increasing luteinizing hormone), DHEA, and estrogen. The design of these research studies, however, has been questioned.
A more recent study found that four weeks of tribulus supplements (at 10 to 20 milligrams per kg of body weight daily) had no effect on male sex hormones testosterone, androstenedione, or luteinizing hormone compared to people who did not take tribulus.
1) Erectile DysfunctionPreliminary animal studies found that tribulus heightened sexual behavior and increased intracavernous pressure. This was attributed to increases in testosterone. There haven't been any well-designed human studies to confirm these early findings.
2) Body Composition and Exercise PerformanceAlthough tribulus has become popular as a sports performance aid, one small but well-designed study found it has no effect on body composition or exercise performance. Fifteen subjects were randomly assigned to tribulus (3.21 mg per kg body weight daily) or a placebo.
After eight weeks with resistance training, there were no changes in body weight, percentage fat, dietary intake, or mood in either group. What was surprising was that muscle endurance actually improved more in the placebo group. Muscle endurance (determined by the maximum number of repetitions at 100 to 200% of body weight) increased for the bench and leg presses in the placebo group. The tribulus group experienced an increase in leg press strength only.
DosageTribulus terrestris is often taken at a dose between 85 to 250 mg three times daily, with meals.
SafetyPregnant or nursing women should not use tribulus.
An increase in breast size (called gynaecomastia) in a young male weight trainer was reported after he took a herbal tablet containing tribulus.
People with hormone-dependent conditions, such as breast or prostate cancer, should not use tribulus.
Tribulus terrestris has a toxic effect in sheep. It has been found to cause a chronic, progressive, irreversible disorder in the dopamine circuits of the nigrostriatal complex in the brain, resulting in impaired muscle function and weakness in the hindquarters, eventually leading to death.
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Phillips OA et al. "Antihypertensive and vasodilator effects of methanolic and aqueous extracts of Tribulus terrestris in rats". Journal of Ethnopharmacology. 104.3 (2006):351-5.