Theory:
The idea behind tribulus is that it may increase testosterone levels indirectly by raising blood levels of another hormone, luteinizing hormone (LH). LH is a hormone produced by the pituitary gland and plays a role in regulating natural testosterone production and serum levels.
Scientific Support:
The active ingredient in tribulus is unknown, but is though to be a component known as furostanol saponins. There has been very little research conducted on the effectiveness of tribulus in elevating testosterone levels – the main claim made by body building products which contain the herb. In some cultures, the tribulus terrestris plant has been used as a "tonic" to in crease energy levels and treat sexual dysfunction (usually in males). In animals, tribulus may stimulate "mounting" behavior. Some European studies suggest that tribulus extract can increase testosterone levels 30-50% above baseline levels – but still well within the normal range. Unfortunately, however, these same studies also suggest a similar increase in estradiol levels – not exactly what the hardcore muscle builders should be interested in boosting
If tribulus extract does indeed elevate testosterone levels somewhat, but keeps them within normal ranges, it may be an effective supplement for individuals with reduced testosterone levels such as athletes at risk for overtraining syndrome and in those individuals on a prolonged low-calorie diet. It will not, however, cause you to start sprouting muscles from all parts of your body, as many body building mags would have you believe.
In one of the few well-controlled studies to examine the effects of tribulus terrestris on body composition and exercise performance looked at 15 resistance-trained males. Subjects received either a placebo or a large dose of tribulus (1.5mg per pound of body weight per day for 2 months). Results showed no changes in body weight, percentage fat, total muscle mass or muscle strength related to tribulus supplementation.
Safety:
Although no significant side effects should be expected at doses of tribulus contained in commercial dietary supplements, animal studies have suggested the possibility of locomotor (muscle coordination) disturbances following ingestion of tribulus in high quantities. In sheep consuming tribulus plant for several months, neurological disease was characterized by an irreversible, asymmetrical, weakness of the hindlimbs.
Value:
Products containing tribulus are typically marketed to bodybuilders and athletes concerned with increasing muscle mass and strength. Although such products are typically combinations of ingredients which include tribulus, rather than tribulus alone, the scientific evidence for product effectiveness is typically lacking. At this time, Supplement Watch does not view tribulus extract (on its own) as a valuable dietary supplement for muscle building. As a support ingredient contained in a wider supplement blend, tribulus may provide some benefits to those individuals interested in maintaining testosterone levels in the normal range (overtrained athletes and dieters).
Dosage:
A typical dosage of 250-1500 mg of tribulus per day is fairly common. Be sure to choose an extract standardized for at least 30-45% steroidal saponins (furostanol).
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