Tribulus for postmenopausal women: impacts on libido and symptoms
“Tribulus has also been shown to increases libido in women, particularly in postmenopausal women, indicating an increase in testosterone levels, and to reduce the severity of the symptoms of menopause.”
Tribulus terrestris is an annual plant in the Zygophyllaceae or caltrop family, with spiny fruit, yellow flowers and sharp thorn-like seeds. While originating in southern Eurasia and Africa, it has spread worldwide and is a hardy invasive species, being known as a noxious weed, partly because of its ability to survive but also because the thorny seeds can easily penetrate many surfaces including human skin and the mouths of grazing animals, generating painful wounds. Tribulus terrestris has many common names, including puncture vine, bindii, goat’s head, devil’s thorn and tackweed.
Tribulus has been used traditionally in multiple ways, particularly in Ayurvedic medicine. For centuries it was mainly used to treat sexual dysfunction and venereal disease and for conditions affecting the liver, kidney, cardiovascular and immune systems.
The whole plant, leaves and seeds of tribulus are used, and contain over 70 known active compounds. The major constituents of this plants are steroidal saponins such as the terrestrosins, desgalactotigonis, furostanol and spirostanol saponoside, which are the predominant actives for improving libido and sexual performance. They also contain alkaloids and common phytosterols such as β-sitosterol, stigmasterol, a cinnamic amide derivative terrestiamide and flavonoids such as quercetin.
The fruit of tribulus contains glycosides, especially saponin glycosides. The saponins on hydrolysis yields diosgenin, ruscogenin etc. Tribulus also contains vitamin C, potassium and calcium.
Substantial clinical trials are still needed, but there has been research on animals for many years. The effectiveness in human trials was determined more by the quality of the plant material and the concentration of specific active ingredients, which are significantly influenced by geographical regions.
Male reproductive system
Tribulus has been shown to improve erectile dysfunction and enhance sexual performance in men, as well as improving sperm count and quality, possibly due to its androgen-enhancing properties, increasing testosterone. While studies have shown that testosterone is improved in androgen-deficient men (at 750mg a day for three months), evidence also shows that other biological mechanisms of this plant are likely to produce this effect.
Tribulus was used traditionally as an aphrodisiac and tonic, especially for male sexual health and performance. While it has been shown that tribulus can increase testosterone levels in men with an androgen deficiency, in a meta-analysis a significant testosterone increase was more likely in animal studies. As a single treatment, increased testosterone levels in humans was limited. However, tribulus increases nitric oxide levels, which could also explain the observed aphrodisiac properties of this plant, independently of testosterone levels. A clinical trial in 90 male subjects over 12 weeks showed a significant improvement in erection, libido and orgasmic function in the treated group compared to placebo.
Tribulus has also been shown to increases libido in women, particularly in postmenopausal women, indicating an increase in testosterone levels, and to reduce the severity of the symptoms of menopause.
Athletic performance and bodybuilding
Small clinical trials have shown improvement in muscle power and aerobic activity in young males supplemented with 1875mg of tribulus for 20 days. Rat studies are showing more promise where tribulus supplementation has increased muscle weight and the performance of rats undergoing high-intensity exercise by triggering an increase in androgens and insulin growth factor.
Extracts of tribulus fruit have demonstrated anti-inflammatory effects by downregulating nuclear factor kB (NFkB), a major inflammatory pathway that has a role in various cancers, and by inhibiting the COX-2 pathways of inflammation.
Extracts of tribulus have been shown to delay postprandial hyperglycaemia by inhibiting the enzyme alpha-glucosiderase, promoting insulin secretion, and influencing beta-cell regeneration in diabetic rats, overall having an antidiabetic effect. Tribulus also improves insulin signalling through insulin-like growth factor (IGF).
Clinical trials showed that tribulus lowered both glucose levels and LDL and total cholesterol in diabetic women. Trials both on men and women are showing that there is a correlation between testosterone and type-2 diabetes, a lower testosterone level in men being a predictor of higher risk for type-2 diabetes. Androgens have also been shown to increase carbohydrate tolerance.
Antiurolithiatic and diuretic
In rat studies tribulus showed a significant diuretic effect, possibly due to a high concentration of potassium salts. Tribulus also reduced high oxalate levels in rats by inhibiting the enzyme glycolate oxidase involved in oxalate formation, thus inhibiting calcium oxalate crystal formation and growth and normalising kidney lactate dehydrogenase (LDH). An extract of the fruits in particular conferred protection against the formation of kidney stones and repaired cell damage from the stones.
The saponins in tribulus have been shown to dilate coronary arteries and improve circulation of the heart, reducing myocardial ischaemia and acting as a cardiotonic. Tribulus protects against atherosclerosis, and the fruits have been shown to lower blood pressure in hypertensive rats, working through the ACE receptors.
Tribulus fruit has demonstrated antibacterial, antiparasitic and larvicidal activity against a range of pathogenic organisms, including malaria and dengue fever, as well as activity against bacteria causing dental caries.
Avoid tribulus if allergic. Animal studies have shown possible photosensitivity, so avoid excessive sun exposure while taking this herb. Safety has not been established in pregnancy and lactation.
Dr Karen Bridgman is a holistic practitioner at Lotus Health and Lotus Dental in Neutral Bay.