Tribulus Terrestris and Testosterone: Scientific Review on Benefits and Side Effects
Tribulus is perhaps the most common ingredient added to test booster supplements, but does it actually work? In this article I will dive into everything you need to know about its interaction with testosterone.
What is Tribulus Terrestris?
Tribulus Terrestris is an annual plant that is native to the warm and tropical climates of southern Europe, southern Asia, Africa, and Australia (1). It has been used in Traditional Chinese Medicine for cardiovascular health and in Ayurvedic Healing (an ancient branch of Indian Herbal medicine) to enhance aspects of male health. Today, it is a commonly added ingredient to muscle-building and test booster supplements.
Tribulus goes by many names. You may have heard it reffered to as goat's-head, cat's-head, devil's eyelashes, devil's-thorn, devil's-weed, puncture vine, or even tackweed.
Like any herb, tribulus contains a variety of compounds. The primary of these is a steroid saponin called Protodioscin (2). In theory, steroid saponins should allow the body to manufacture more of its own androgens and speed up protein synthesis. But as you'll see, this effect doesn't carry out in practice.
Does Tribulus Increase Testosterone Levels In Humans?
In this section of the article I'll go over the 3 human studies that observed the impact of tribulus supplementation on testosterone levels. I emphasize human studies because conclusions drawn from animal and test-tube studies usually don't carry on to affect us the same way.
Considering the popularity of tribulus, I was expecting to find more than 3 human studies, but it seems like the popularity of an ingredient is not usually driven by science.
Human Trial #1
Number of Subjects
22 elite male rugby players (aged 17-22) were randomly assigned to ingest a daily dose of either 450mg of tribulus or placebo.
All subjects also underwent heavy resistance-training as per their usual pre-season preparations.
Muscular strength, body composition, and testosterone levels were measured before and after the 5-weeks of treatment.
Although 5-weeks of training increased strength and lean mass, no differences were noted in subjects between groups. Testosterone levels also remained relatively the same.
My takeaway: In young elite athletes, supplementing with tribulus had no impact on strength, muscle, or testosterone levels.
Human Trial #2
Number of Subjects
21 healthy men (aged 20-36) were randomly assigned to ingest a daily dose of either 20mg of tribulus/kg of bodyweight, 10mg of tribulus/kg of bodyweight, or placebo.
Serum testosterone levels were measured 24 hours before treatment and at varying time intervals during the course of the study.
After 4 weeks, no significant differences in T were noted amongst subjects. Placebo had about the same testosterone levels as the subjects given varying doses of tribulus.
My takeaway: Once again, tribulus supplementation had no impact on testosterone levels whatsoever.
Human Trial #3
Number of Subjects
63 subjects (aged 21-50), with low sperm count, were randomly assigned to receive a daily dose of either 6g of tribulus (twice a day) or placebo for 60 days.
Semen analysis and serum testosterone levels were measured before and after 60 days of treatment.
Subjects supplementing with tribulus had improved markers of penile performance and significantly reduced fatigue. In these men, testosterone levels also increased by an average of 16.3%
My takeaway: This is the first study that found a positive interaction between tribulus supplementation and testosterone. But keep in mind that the subjects were infertile. And even still, T-levels only increased by 16.3%; nowhere near enough to experience any noticeable differences. Also, the dosage was 12g, which is more than you'll find in any test booster on the market.
The Bottom Line: Tribulus Doesn't Increase Testosterone In Otherwise Healthy Males
Based on the two out of three human studies cited above, tribulus supplementation fails to have any impact on testosterone levels. In the one study that it did increase testosterone levels was in infertile men.
The question then becomes:
If tribulus is proven not to increase testosterone levels, why do manufacturers continue to add it to their supplements?
Well, the first reason is because tribulus appears to boost libido. Libido-enhancing herbs are often added to test boosters to make the user feel like its working. The reality is, that although higher testosterone leads to higher libido, the inverse is not necessarily true, i.e. tribulus increases sex drive without having an impact on testosterone.
The second reason is because tribulus is "scientifically proven" to boost testosterone levels...in animals. For example, primates injected with tribulus experienced a 50% increase in total T (3). A similar effect was seen in rats (4). But just because something has been shown to have an effect in animals doesn't mean that it carries on to affect humans in the same way. Be wary of animal studies being cited as "scientific proof".
And finally, tribulus also contains steroidal saponins. These are compounds found primarily in plants that are considered to be the building blocks of steroids that help the body increase production of its own androgens. And although concentrated forms of steroidal saponins have been found to boost testosterone levels in animals, the research with humans is limited. But it seems like, with tribulus, these compounds are not appropriately absorbed by the human body and therefore unable to exert their influence.
Bottom Line: Even though tribulus has been showed in peer-reviewed literature to have no impact on testosterone levels, companies continue to add it to their supplements because it boosts libido, has been proven in scientific studies, and contains ingredients that, in theory, should increase testosterone levels.
Tribulus Terrestris for Bodybuilding
As cited in Human Trial #1 above, elite athletes supplementing with 450mg of tribulus did not experience any differences in strength or body composition.
In another study, 15 resistance-trained males were randomly assigned to ingest a daily dose of placebo or 3.21mg of tribulus/kg of bodyweight. After 8-weeks of supplementation, both groups gained similar amounts of strength on the leg press. Surprisingly, placebo gained significantly more strength on the bench press (4).
So based on these two human studies tribulus either has no effect on muscle gain, or it can even cause a decrease in upper body strength.
Bottom Line: Tribulus has no impact on muscle growth or strength. In fact, it may actually slow down upper body gains.
Does Tribulus Have Any Benefits?
All the research so far has bashed on tribulus so hard that at this point you might find it hard to imagine why anyone would even supplement with it. But although it doesn't have any affect on athletic performance or hormones, tribulus does appear to provide cardiovascular benefits (5).
In Traditional Chinese Medicine, tribulus was used to help with eye issues, edema, and high blood pressure. In Ayurveda, it has been used to treat lower back pain, sciatica, inflammation of the pelvic and sacral region, dry cough, respiratory disorders. Although there is not much scientific evidence to back these benefits up, it is still interesting to note considering these branches of herbal medicine have been around for thousands of years.
Tribulus Side Effects
According to WebMD, tribulus terrestris supplementation is possibly safe for most people. The time-span, however, is only measured up to 8 weeks. Due to a lack of long-term studies, the long-term safety of tribulus is unknown.
The Down and Low On Tribulus Terrestris
Tribulus Terrestris may be a popular test boosting ingredient, but studies show that it has no impact on testosterone levels.
I've listed some benefits of it above, but if you're considering it for the enhancement of your athletic performance, you're better off trying out something else.
This article was meant to provide you with an understanding of tribulus, but I hope that it also provided you with insight towards how the supplement industry functions. They are not heavily regulated by the FDA and therefore have a wide area of freedom around the claims they are able to make.
If you take one thing from this article, it should be to research any supplement before ingesting it. Never go by the claims made on the label.
TL;DR: Supplementing with tribulus terrestris has no influence on testosterone levels in otherwise healthy men. Even in infertile men, the influence is not significant.