Tribulus terrestris: what it is and how it works
Tribulus terrestris is one of the most heavily marketed herbal products in gym culture, sold for decades as a natural way to raise testosterone. Our editorial team looked at where the plant comes from, how it is supposed to work and what controlled studies in real athletes have actually found.
What tribulus actually is
Tribulus terrestris is a low, spreading plant of the caltrop family that grows in warm, dry regions of southern Europe, Asia, Africa and Australia. Its spiky fruits are notorious for puncturing bicycle tyres and bare feet, which explains common names such as puncture vine and goathead. In traditional Ayurvedic and Chinese medicine, the fruit and root were used for urinary complaints, low libido and general vitality.
The supplements sold in the UK today are almost always dried extracts of the aerial parts or fruit, standardised to a percentage of so-called saponins. The best known of these compounds is protodioscin, a steroidal saponin that manufacturers often quote on the label as a marker of quality. Extracts may claim anything from 40% to over 90% saponins, although independent testing has shown that labels do not always match contents.
Chemically, the saponins in tribulus vary considerably depending on where the plant was grown. Analyses comparing samples from Bulgaria, Turkey, India and elsewhere found that the protodioscin content can differ by an order of magnitude. That variability matters, because a product made from one source may have little in common with the extract used in a published study.
In the sports nutrition market, tribulus became famous in the 1990s on the back of claims that Eastern European strength athletes used it to boost natural testosterone. That story, more marketing than science, still shapes how the product is sold: as a "natural testosterone booster" for men who lift weights.
The proposed mechanism and why it is shaky
The original hypothesis was that protodioscin stimulates the release of luteinising hormone (LH) from the pituitary gland, which in turn signals the testes to make more testosterone. Some early animal experiments, mainly in rats, rabbits and primates, reported increases in certain androgens or in erectile function after high doses of extract.
Translating those findings to people has proved difficult. Animal doses were often far higher per kilogram of body weight than anything a person would take, and several of the studies were small, unblinded or published in journals with limited peer review. Human trials measuring LH and testosterone directly have largely failed to show the expected rise.
A frequently cited trial by Neychev and Mitev gave young healthy men tribulus for four weeks and found no change in testosterone, androstenedione or LH compared with placebo. A later systematic review by Qureshi and colleagues reached a similar conclusion: the evidence for hormonal effects in humans is weak, and positive results tend to come from studies of men with existing fertility or sexual problems.
Other mechanisms have been suggested, including effects on nitric oxide signalling in erectile tissue and mild antioxidant activity. These ideas may explain some reports of improved sexual wellbeing, but they are not the same as building muscle or strength. For athletes, the hormonal pathway is the one that matters, and it is the one with the least support.
What the research shows for training and body composition
Controlled studies in people who train have been consistently disappointing for those hoping for a performance edge. Antonio and co-workers gave resistance-trained men tribulus or placebo over eight weeks and found no meaningful difference in body composition, strength or muscular endurance between groups.
A study in elite rugby league players during pre-season training reached the same verdict. Rogerson and colleagues reported that both the tribulus group and the placebo group got stronger and leaner, which is exactly what you would expect from structured training, but the supplement added nothing measurable on top.
Where tribulus shows some promise is in sexual function. Several randomised trials, particularly in men with reduced libido and in women with hypoactive sexual desire, have reported modest improvements on questionnaire scores. These findings are interesting but are not evidence of an anabolic effect, and the effect sizes are small.
The International Olympic Committee consensus statement on supplements for elite athletes does not list tribulus among products with good evidence for performance benefit. In practice, sports dietitians in the UK rarely recommend it, preferring to spend an athlete's budget on items such as creatine, caffeine or protein, which have solid data behind them.
Safety, quality and anti-doping considerations
At the doses used in trials, commonly 250–750 mg of extract a day for up to a few months, tribulus has generally been well tolerated. Reported side effects include stomach upset, reflux and occasional sleep disturbance. There are isolated case reports of liver and kidney problems, but causality is hard to establish because products were often of unknown composition.
Tribulus is not on the World Anti-Doping Agency Prohibited List. The bigger concern for tested athletes is contamination. Pokrywka and colleagues, writing about tribulus products used by athletes, highlighted that herbal "testosterone boosters" are a category with a known history of adulteration with anabolic agents.
UK Anti-Doping advises athletes to use only batch-tested products and to check them through an independent screening programme. That advice applies with special force to anything marketed for hormones or muscle gain, where the commercial temptation to spike a product is highest.
- Avoid tribulus during pregnancy and breastfeeding, as there are animal data suggesting possible harm to foetal development.
- Seek medical advice if you take medicines for blood pressure, diabetes or heart conditions, as interactions have been theorised.
- Stop using it and see a doctor if you notice yellowing of the skin, dark urine or persistent abdominal pain.
Should you take it? A practical comparison
If your goal is more muscle and strength, the honest answer from the current literature is that tribulus is unlikely to help. The money and attention are better directed towards training quality, total protein intake, sleep and, if you want a supplement, creatine monohydrate.
| Claim | What human studies suggest | Editorial verdict |
|---|---|---|
| Raises testosterone | No consistent rise in healthy men | Not supported |
| Increases strength | No advantage over placebo in trained people | Not supported |
| Improves body composition | No meaningful change in lean or fat mass | Not supported |
| Supports libido | Modest effects in some trials | Possible, more data needed |
For men experiencing low libido, fatigue or loss of muscle, a supplement should not be the first step. These symptoms can have many causes, including genuine hypogonadism, thyroid disease, depression or overtraining, and a GP can arrange blood tests to look for them.
If you still choose to try tribulus out of curiosity, pick a product with a clear extract specification and independent testing, use it for a defined period, and judge it honestly. Keep a simple log of training performance and wellbeing so that you are not relying on memory or expectation.
Editorial conclusions
Tribulus terrestris is a traditional herbal remedy that the sports market reinvented as a testosterone booster. The rebrand has outrun the science: in healthy, training adults it does not reliably raise testosterone, strength or lean mass.
The most credible use is in sexual wellbeing, where small trials show modest benefits. Even there, the evidence is not strong enough for confident recommendations.
Safety at studied doses appears reasonable, but product quality varies and contamination is a real risk for tested athletes.
For related reading, see our guides to creatine monohydrate, what a testosterone blood test can and cannot tell you, and how to check supplements for anti-doping safety.
References
- Neychev VK, Mitev VI. The aphrodisiac herb Tribulus terrestris does not influence the androgen production in young men. J Ethnopharmacol. 2005;101(1–3):319–323.
- Antonio J, Uelmen J, Rodriguez R, Earnest C. The effects of Tribulus terrestris on body composition and exercise performance in resistance-trained males. Int J Sport Nutr Exerc Metab. 2000;10(2):208–215.
- 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;21(2):348–353.
- 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;11(1):64–79.
- Pokrywka A, Obmiński Z, Malczewska-Lenczowska J, et al. Insights into supplements with Tribulus terrestris used by athletes. J Hum Kinet. 2014;41:99–105.
- Maughan RJ, Burke LM, Dvorak J, et al. IOC consensus statement: dietary supplements and the high-performance athlete. Br J Sports Med. 2018;52(7):439–455.
