Supplement research

Tribulus

What is Tribulus?

Tribulus Terrestris is an annual plant that is used in herbal preparations.

Proposed Benefits of Tribulus

It is theorised that tribulus increases testosterone levels which would increase muscle mass and strength. It is also proposed that tribulus will prevent the formation of estrogens when androgens are ingested. One of the reported problems with administration of prohormones (i.e. precursors to testosterone) is that they increase oestrogen levels. It is proposed that tribulus may prevent this conversion.

Mechanism of Action of Tribulus

It is proposed that Tribulus Terrestris increases testosterone levels indirectly by increasing the release of luteinizing hormone from the pituitary, thereby resulting in greater production of testosterone from the testes.

Research on Tribulus

Several studies have investigated the effects of supplementation with Tribulus terrestris. Most of these studies suggest that tribulus does not increase testosterone levels.

A study by Brown et al showed that tribulus did not prevent the conversion of androgens to oestrogens (1).  In addition, total testosterone was not increased with supplementation. A further study by this group showed that the addition of tribulus to androstenedione (an androgen) supplementation does not result in increased blood testosterone concentration or reduce the estrogenic effect of androstenedione (2). In addition there were not improvements to adaptations to resistance exercise.

A further study looked solely at the effects of tribulus on body composition and exercise performance in resistance-trained males (3). Fifteen subjects were randomly assigned to receive tribulus (3.21mg/kg of body weight/day) or a placebo. There were no changes in body weight, percentage fat or total body water in either group.

Rating of Efficacy for Tribulus

Tribulus does not appear to be effective at increasing testosterone levels and increasing muscle mass.
3/10

References

1.  Brown G.A., Vukovich M.D., Martini E.R., Kohut M.L., Franke W.D., Jackson D.A. and King D.S. Effects of androstenedione-herbal supplementation on serum sex hormone concentrations in 30- to 59- year-old men. Int J Vit & Nutr Res. 71:293-301, 2001.
2.  Brown G.A., Vukovich M.D., Reifenrath T.A., Uhl N.L., Parsons K.A., Sharp R.L. and King D.S. Effects of anabolic precursors on serum testosterone concentrations and adaptations to resistance training in young men. In J Sport Nutr & Ex Metab. 10:340-359, 2000.
3.  Antonio J., Uelmen J., Rodriguez R. and Earnest C. The effects of Tribulus terrestris on body composition and exercise performance in resistance-trained male. Int J Sport Nutr & Ex Metab. 10:208-215, 2000.