-popularized in USA in early 1970’s
-marketed as testosterone-enhancing supplement
-the only effective form is the specially cultivated Bulgarian tribulus
-other forms never shown to produce the hoped-for effects in scientific studies
Tribulus terrestis is an excellent example of a herb that can have completely different properties when grown under different conditions.
Tribulus gained its fame by being used with great success by Bulgarian weightlifters who were (and still are) using a special form long cultivated to contain the ideal amounts of various saponins (mostly of furostanol type) in very specific ratios.
While several scientific studies and a long anecdotal evidence has shown the effectivity of Bulgarian tribulus as produced by the largest Bulgarian pharmaceutical company Sopharma, other forms of tribulus extracts have been shown virtually useless.
The explanation is actually quite simple: according to a scientific paper published in Phytochemistry Journal in 2008 “Distribution of steroidal saponins in Tribulus terrestris from different geographical regions” (http://www.ncbi.nlm.nih.gov/pubmed/17719068), there are two different species of tribulus terrestris.
The species prevalent in southern Europe (Bulgaria, Greece, Turkey) differs greatly from the one to be found in Asia (India, Vietnam). The Asian Tribulus Terrestris is completely missing some of the most effective saponins while being rich in others with little effect on male hormonal profile.
So while the clinical trials with south-European tribulus confirmed its effects on testosterone levels (Clinical trial of a tribestan preparation in infertile men, http://www.ncbi.nlm.nih.gov/pubmed/6367515 Use of tribestan on rams with sexual disorders, http://www.ncbi.nlm.nih.gov/pubmed/3629956 The influence of the Tribulus terrestris extract on the parameters of the functional preparedness and athletes' organism homeostasis, http://www.ncbi.nlm.nih.gov/pubmed/20095389) no benefits have been found with generic tribulus of Asian origin (The effect of five weeks of Tribulus terrestris supplementation on muscle strength and body composition during preseason training in elite rugby league players, http://www.ncbi.nlm.nih.gov/pubmed/17530942 The effects of Tribulus terrestris on body composition and exercise performance in resistance-trained males, http://www.ncbi.nlm.nih.gov/pubmed/10861339).
The main active compounds in Tribulus terrestris:
Prototribestin (missing in Asian variety)
Tribestin (missing in Asian variety)
Tribulosin (higher levels in Asian variety)
There are several other steroidal saponins present in Tribulus – in fact the list of active substances is growing with new research and goes in thousands.
Tribulus is thought to increase the levels of natural testosterone (and estrogen in females) by direct stimulation of the release of Luteinizing hormone and Follicle-stimulating hormone.
Those two hormones are in turn responsible for production of sex hormones in both men and women.
This suggests that the effects of active compounds in Tribullus terrestris actually resemble the action of GnRH (Gonadotropin-releasing hormone).
The drug-test myth
Tribulus terrestris has never been found to elevate the testosterone profile to such levels that could have lead to positive anabolic-steroid testing.
It is possible that some athletes with doping history tried to blame the legal Tribulus but the Bulgarian weightlifters who openly use Tribulus have never been tested positive.
The traditional use of Tribulus is for loss of libido and erectile dysfunction. Unlike anabolic steroids which will inevitably cause prolonged and painful periods of complete loss of libido, Tribulus has exactly the opposite effects.