Traditional medicine can seem to be at odds with so-called Western medicine, in part because the basis of Western medicine is the scientific method. And in that method, one must prove that a substance works beyond all chance of coincidence or accident.
With some traditional medicines, like ginseng, there are dozens of studies supporting its various uses, and these data are beyond dispute. And yet there is resistance to implementing those traditional remedies.
In other cases, like with the herb Tribulus terrestris and testosterone, the jury is still out. This makes the decision to include it in a normal remedy for something like low testosterone difficult to make.
Key Findings
✲ Significant bodies of evidence support the mechanism for increasing testosterone in animals after treatment with Tribulus.
✲ Human studies, however, have been inconsistent, with some evidence pointing either way.
✲ The exact mechanism of Tribulus and its effect on testosterone are not well-understood, making determinations of data difficult.
✲ No known side effects have been reported, but scant data exists on long-term use.
Enough Evidence to Support a Correlation
There are a number of documented scientific studies showing that Tribulus can increase a number of testosterone markers in animals–including increased sperm count, increased sperm motility, and increased serum testosterone levels. Interestingly, the link I shared above goes beyond journals–those are excerpts from actual textbooks.
In order for something like a traditional herb to make the leap from “herbal medicine” into the realm of textbooks requires an extraordinary amount of peer-review and robustness of data. This is because a textbook costs millions of dollars to publish–dollars lost if that text book were found to make erroneous claims.
This does, however, bring us to the next point–none of those same results are consistently seen in human studies.
Not Enough Evidence for Causation
If something were truly causal–this herb causes this effect–it must be demonstrated across species and conditions. For instance, almost with no exceptions, tobacco leads to ill-health. That’s a causal relationship.
With Tribulus, great pains have been taken to find some kind of relationship to testosterone, because the links in animal studies have been so compelling. Unfortunately, the bulk of human studies have not supported any such relationship. One main conclusion from the study I linked above is that only men with normal testosterone levels have been studied, compared with testosterone-deficient animals.
It could very well be that Tribulus only has an effect on men with low-testosterone, but none of the available science has delved into the reasons why it may work–though some have hypothesized the ability of Tribulus to increase nitric oxide.
Other suggestions on why it hasn’t worked in humans are that we have differing biology and that the animal studies had other variables. One researcher went so far as to suggest that the wrong form of Tribulus was studied in humans.
One study, published in the Journal of Dietary Supplements, noted this discrepancy in data, and stated that the best effect of Tribulus can be seen in supplements that combine the herb with other ingredients–though their public data don’t delve into which other ingredients those might be.
Conclusion
As a researcher, I feel my best when I can find studies refuting a claim outright, or when I find so many studies confirming a claim that I can start to research the mechanisms. In some cases, I can find that no published research, whatever, has been done, which usually leads to some level of confidence that there’s no basis to the health claim because no one has seen the merit of investigating.
I find I have the least confidence in findings such as these. I have found textbooks claiming that Tribulus works–with the reputations of authors, publishers, libraries, and professors all on the line. But those claims only extend to animal studies. In the human studies we see the results split right down the middle.
Until direct, multi-faceted studies are conducted to determine the actual mechanisms of Tribulus, we cannot know if the effect of increased testosterone is because of the herb, itself, or some other factor.