Tribulus terrestris

Tribulus terrestris is a herb from Ayurveda that is mostly recommended for male health including virility and vitality, and specifically more catered towards cardiovascular and urogenital health. It is a common supplement for its libido enhancing properties and supposed testosterone boosting properties.

On the sexual side of things, tribulus does appear to be a relatively reliable and potent libido enhancer in rats and the lone human study assessing this has confirmed an increase in sexual well being and erectile function. While it is not exactly known how tribulus works, it is known to enhance androgen receptor density in the brain (muscle tissue not confirmed) which may enhance the libido enhancing properties of androgens. Limited evidence suggests that it is weak to non-effective in enhancing fertility.

A specific component, tribulosin, appears to be quite potently cardioprotective and is effective in the 1-10nM range. It has not yet been tested in living creatures, but remains a very promising option.

In animal research, the fruits of tribulus appears to protect the organs (mostly liver and kidneys) from oxidative damages at reasonably low dosages and also exert anti-stress effects; confirming the status of tribulus terrestris as an adaptogen.

Despite the above promise as an adaptogen and a libido enhancer, studies investigating tribulus in sports performance have all failed to find benefits. The herb seems to be a possibly healthy herb that enhances sexuality but with limited use for power output and testosterone enhancement (which it has repeatedly failed to do).

Given a 60% saponin extract, a dose of between 200-450mg a day is typically used for libido enhancement and sexuality. If rodent research applies to humans, then the dosage of 5mg/kg of tribulus terrestris saponins which is seen as the optimal dose would correlate to a human dose of:

• 55 mg saponins (90 mg of a 60% extract)

• 70 mg saponins (120 mg of a 60% extract)

• 90 mg saponins (150 mg of a 60% extract)

Which suggests low doses are better. If a concentrated extract is not used, traditional dosages of the basic root powder are in the 5-6g range while the fruits are in the 2-3g range.

The Human Effect Matrix looks at human studies (it excludes animal and in vitro studies) to tell you what effects tribulus terrestris has on your body, and how strong these effects are.

Grade	Level of Evidence [show legend]
	Robust research conducted with repeated double-blind clinical trials
	Multiple studies where at least two are double-blind and placebo controlled
	Single double-blind study or multiple cohort studies
	Uncontrolled or observational studies only

Level of Evidence ? The amount of high quality evidence. The more evidence, the more we can trust the results.	Outcome	Magnitude of effect ? The direction and size of the supplement's impact on each outcome. Some supplements can have an increasing effect, others have a decreasing effect, and others have no effect.	Consistency of research results ? Scientific research does not always agree. HIGH or VERY HIGH means that most of the scientific research agrees.	Notes
	Testosterone	-	High See all 8 studies	In otherwise healthy males, testosterone is not influenced with supplementation of tribulus terrestris. There may be an increase in infertile men, but this is weak. There may be a small effect in postmenopausal women with low libido, however, the difference wasn't statistically significant.
	Blood Pressure	Minor	Very High See 2 studies	A decrease in blood pressure has been noted in hypertensive subjects in one study. Another larger study in normotensive subjects failed to find a significant change. More studies in hypertensive subjects are needed before confidence in the effect is warranted.
	Diuresis	Minor	- See study	3g of the fruits or a water extract thereof appears to increase overall urine volume after a month of supplementation by around 200mL daily.
	Erections	Minor	Very High See all 4 studies	1.5 and 2.25 of tribulus extract or 6 g of tribulus root seems to modestly improve erections in infertile men, men with partial androgen deficiency, and men with erectile dysfunction. The effect is reliable across all studies so far, however, research is still in its early stage and great confidence in these results would be unwarranted.
	Heart Rate	Minor	- See study	A decrease in heart rate has been observed in hypertensive persons given tribulus supplementation
	Libido	Minor	Very High See all 5 studies	Most studies found an improvement in sexual desire in women reporting a general loss of libido. One study in men found an improvement. The research is still in its early stage and great confidence in these results would be unfounded.
	Fat Mass	-	Very High See all 3 studies	No significant influences on fat mass are noted with tribulus terrestris
	Fatigue	-	Moderate See 2 studies	Exercise related fatigue and vigor is unaffected by tribulus supplementation in trained men
	Lean Mass	-	Very High See all 3 studies	Insufficient evidence to support a consistent increase of lean mass associated with tribulus relative to placebo during training or in general.
	Luteinizing Hormone	-	Very High See all 4 studies	A consistent influence on luteinizing hormone hasn't been detected with supplemental tribulus
	Power Output	-	Very High See 2 studies	No significant alterations in power output associated with tribulus supplementation.
	Sperm Count	-	Very High See all 3 studies	Only one uncontrolled trial has found an increase in sperm count with supplementation of 2.25 g of Tribulus extract daily. One study found an increase but it wasn't significant, and one that used 6g of tribulus root didn't find a significant increase compared with control.
	Sperm Quality	-	Very High See 2 studies	The increase in sperm quality seen with 6g tribulus root has failed to outperform placebo in infertile men. Another uncontrolled study that used 2.25 g per day of a tribulus extract found significant improvements in multiple measures of semen/sperm quality.
	Total Cholesterol	-	- See all 3 studies	A decrease in cholesterol levels has been noted with tribulus supplementation in some studies. However, the largest study found no significant decrease, and none of the studies have made cholesterol their primary endpoint.
	Seminal Motility	Notable	- See study	One uncontrolled study found a notable improvement in seminal motility relative to baseline
	Blood Glucose	Minor	- See study	One randomized, controlled trial found a modest reduction in fasting and 2 hour postprandial glucose when taking 1 g/d of a Tribulus extract
	DHT	Minor	- See study	An increase of DHT has been noted in one study.
	HbA1c	Minor	- See study	One randomized, controlled trial found a modest reduction, accompanied by reduced fasting and postprandial glucose levels.
	Prostate Specific Antigen	Minor	- See study	One study found a significant increase relative to placebo with 2.25 g of a tribulus extract per day.
	Sexual Function	Minor	High See all 4 studies	There may be a small improvement in overall sexual function in premenopausal women with libido taking 2.25 g/d of a tribulus extract. Effects on postmenopausal women are unclear.
	DHEA	-	Moderate See 2 studies	One study found an increase with 2.25 g of Tribulus per day for 12 weeks, however, a larger study found no significant difference.
	Follicle-Stimulating Hormone	-	- See study	No change in one uncontrolled study
	Free Testosterone	-	High See all 3 studies	One uncontrolled study found a small but significant increase from baseline, but the other studies found no significant difference.
	HDL-C	-	Moderate See 2 studies	No apparent effect
	LDL-C	-	Moderate See 2 studies	One study found a modest, significant reduction relative to placebo. Another study found a small, non-significant reduction
	Liver Enzymes		- See study	One study found a small increase in AST but not ALT
	Prolactin	-	- See study	One study found a reduction in Prolactin relative to baseline, however, this isn't statistically significant
	Sex Hormone Binding Globulin	-	- See study	No significant change in men taking 1.5 g/d of a Tribulus extract
	Triglycerides	-	Moderate See 2 studies	While a modest reduction is possible, the results of two studies didn't find significant differences relative to placebo.

Studies Excluded from Consideration

• Confounded with Murraya koenigii^[1]

• Confounded with N-Glucosamine, D-Acetyl-N-Glucosamine, and Ecklonia bicyclis^[2][3]