Tribulus Terrestris has long been a standard ingredient in food supplements touted to boost testosterone levels. Indeed, it's still found in many such "testosterone boosters," despite the publication of several human studies that showed no effect of Tribulus at all on testosterone release in humans. On the other hand, the animal research related to this herb is impressive. It seems to boost libido considerably in species ranging from rats to rams and has long had a reputation as a potent aphrodisiac in Eastern European countries, such as Bulgaria. One reason why the studies related to Tribulus have often shown mixed results relates to the content of active ingredients found in the supplements. These active ingredients are collectively called steroidal saponins, and their content can vary widely in various supplements, depending on the origin of the Tribulus contained in the product. Of the various saponins contained in Tribulus, the most potent is thought to be Protodioscin, which comprises nearly half of the content of the Tribulus. As the name implies, steroidal saponins are structurally similar to human steroid hormones, including both testosterone and estrogen. But just having a structural similarity doesn't mean they will produce the same effects in the body.
The best in terms of active saponin ingredient Tribulus comes from Bulgaria and Turkey. Yet the preponderance of studies that have examined the anabolic effects of the herb has usually used cheaper, and far less potent forms emanating from China and India. These forms usually lack sufficient activity of the contained saponins, so wouldn't be expected to produce many benefits, and that's precisely what the studies showed. The true Bulgarian Tribulus is considered to be the highest quality form of Tribulus in terms of active ingredients. Besides the saponins, Tribulus also contains flavonoids, alkaloids, and amino acids, as well as a respectable amount of vitamin C. All of these compounds can exert effects in the human body, although with the exception of amino acids, don't provide any significant anabolic effects. The saponins in Tribulus may also provide some health effects, such as lowering elevated blood pressure. Some compounds in Tribulus appear to protect heart muscle cells from death due to a massive release of free radicals that occurs following a heart attack. It may also have a minor cholesterol-reducing effect. As noted, early studies of Tribulus showed that it consistently boosted serum testosterone levels in male rats, rabbits, and primates. It wasn't a dramatic leap to expect it to do the same for humans. But while poorly conducted Bulgarian studies did show increased libido or sex drive in men who ingested Tribulus supplements, the later studies that examined the relationship between Tribulus and testosterone failed to show any significant effects.
Rat studies show that Tribulus boosts the number of androgen receptors in the brain. While this wouldn't translate into increased muscular size or strength, it would likely positively affect . . .