Tribulus terrestris: what it does, and why your testosterone stays put

Tribulus terrestris has been tested on testosterone in men, and there was no effect. In 22 rugby players, 450 mg a day for five weeks changed nothing. Strength, fat-free mass and testosterone stayed the same (Rogerson 2007, PMID 17530942).

Neychev followed 21 healthy men aged 20 to 36 for four weeks. Their testosterone then sat at 15.8 and 16.3 nmol/l, against 17.7 on placebo. That difference was not significant (Neychev 2005, PMID 15994038).

What strikes me as a training partner? Tribulus sits next to the protein shakes in every sports shop, with a bull on the label. The two best trials in men found a zero.

Below is what tribulus does do and where the claim comes from. And what to measure if you want to try it anyway.

What is tribulus terrestris?

Tribulus terrestris is a creeping plant with spiky fruits. It grows in southern Europe, Asia and Africa and is known in English as puncture vine. In Ayurveda and Chinese herbal medicine it has long been used for potency.

The active compounds are saponins, mainly protodioscin. Extracts are standardised on them, usually at 40 to 60 percent saponins. Supplement doses run from 250 to 1,500 mg a day.

The testosterone claim comes from animal and lab research. In humans that claim has never been confirmed in a controlled trial. Two Bulgarian researchers concluded that in a review of all the data (Neychev 2016, PMID 26727646).

They are the same researchers who measured the zero in young men themselves.

What does tribulus do to your body?

In men, tribulus does little that is measurable to your hormones. In the Neychev trial the men took 10 to 20 mg per kilo of body weight a day. That is a hefty dose. Testosterone, androstenedione and LH all stayed the same (Neychev 2005, PMID 15994038).

What does recur in the literature: an effect on libido and erections. A 2014 review found signs of a mild aphrodisiac effect. It found no evidence for more testosterone or better athletic performance (Qureshi 2014, PMID 24559105).

That looks like maca. Desire can rise without your hormones moving. The difference is that the evidence for maca is firmer.

For your strength, tribulus did nothing. The rugby players got stronger through their preseason. The placebo group got exactly as strong (Rogerson 2007).

Tribulus and the doping test: the T/E ratio

Rogerson also measured the ratio of testosterone to epitestosterone in urine. That is the T/E ratio, the value a doping test looks at. It did not change (Rogerson 2007, PMID 17530942).

For a tested athlete that is the most useful number in the whole tribulus literature. The supplement does not help you, but it does not make your test suspicious either.

Do watch for contamination. Herbal supplements have repeatedly turned out to be contaminated with substances that are on the doping list. If you get tested, a product with an independent certificate is the safer choice.

What are the side effects of tribulus terrestris?

No serious side effects were reported in the trials in men. Stomach complaints and a restless feeling occur now and then. There are also a few isolated reports of liver and kidney complaints at high doses. A causal link has not been proven.

EFSA has not authorised a health claim for tribulus. A seller is therefore not allowed to say it raises your testosterone. The Dutch Voedingscentrum puts herbal preparations in the same category. No proven benefit on top of a varied diet.

Use it for more than a few months? Then your liver values are the place to look. How those behave with herbal extracts is covered in liver values and supplements in athletes.

What to measure if you try tribulus anyway

Imagine you are 28 and you train five times a week. You want to know whether tribulus does anything for you.

Then you measure twice. Once before you start and once after 8 to 12 weeks. Both in the morning, between 7 and 10.

If your testosterone stays the same, you saw what the trials saw. If it rises, that is interesting, but one reading is not proof. Testosterone swings from day to day and from hour to hour.

Total testosterone, free testosterone and SHBG come together in the hormone panel. The other values are measured separately via the biomarker pages. ALT is measured separately or as an add-on to 360 health. For total testosterone alone, the testosterone test is enough.

What you can do with this

My line is clear. For testosterone or strength, tribulus is money down the drain. I say that with two good trials in hand. For libido the evidence is thin, and maca does the same with better evidence.

If you really want to do something about low testosterone, first find out where it comes from. Which supplements do something measurable, and in whom, is in the overview of testosterone supplements. And maca powder is the more honest choice if desire is your complaint.

If a value is off, discuss it with your GP and mention which supplements you take. Every blood test result includes a professional assessment from a BIG-registered doctor. For treatment decisions, discuss your results with your GP.

References

• Rogerson S, Riches CJ, Jennings C, et al. The effect of five weeks of Tribulus terrestris supplementation on muscle strength and body composition during preseason training in elite rugby league players. J Strength Cond Res. 2007 (PMID 17530942).
• Neychev VK, Mitev VI. The aphrodisiac herb Tribulus terrestris does not influence the androgen production in young men. J Ethnopharmacol. 2005 (PMID 15994038).
• Neychev V, Mitev V. Pro-sexual and androgen enhancing effects of Tribulus terrestris L.: Fact or Fiction. J Ethnopharmacol. 2016 (PMID 26727646).
• Qureshi A, Naughton DP, Petroczi A. A systematic review on the herbal extract Tribulus terrestris and the roots of its putative aphrodisiac and performance enhancing effect. J Diet Suppl. 2014 (PMID 24559105).
• Voedingscentrum. Voedingssupplementen. voedingscentrum.nl.
• EFSA. EU Register of nutrition and health claims. ec.europa.eu/food/safety/labelling_nutrition/claims/register.