Tongkat Ali (Eurycoma longifolia, Simaroubaceae), also known as long jack, is a dioecious flowering shrub widely distributed in Southeast Asia and Indochina. An aqueous decoction of its roots is used traditionally to promote sexual health and fertility and to counter the effects of ageing. It is reported to have anti-inflammatory, antimalarial, antimicrobial, and antioxidant activity. Other traditional uses include as an anxiolytic and for its antiulcer and anticancer effects. Tongkat Ali’s composition includes alkaloids such as β-carboline and cathine-6-one, flavonoids, phenolics, saponins, tannins, propanoids such as scopolin and propan, biphenylneolignans, and triterpenes such as tirucallane and eurylene. It is rich in quassinoids, including eurycolactones A-F, eurycomalactone, hydroxylongilactone, dehydroklaineanone, 15β-O-acetyl-14-hydroxyklaineanone, eurycomanol, eurycomanone, and eurycomaoside, all thought to contribute to its salutary effects on muscle strength, endurance, and reduced anxiety and stress.
These latter effects fall within the realm of ergogenics. An ergogenic aid is defined as any means of enhancing energy use, production, control, or efficiency. Besides mechanical and psychological ergogenic aids, other types are physiological, pharmacological, and nutritional. Pharmacological ergogenic aids might include manufactured drugs as well as natural substances. Consumption of various herbs is a common ergogenic practice, often intended to boost endurance and strength in sports. The authors review evidence regarding the use of Tongkat Ali as an ergogenic aid.
The authors, without disclosing their search strategy, review available evidence concerning ergogenic benefits of Tongkat Ali. Four human studies are discussed. A randomized, double-blind study evaluated the effects of a Malaysian herbal drink containing Tongkat Ali (0.1 mg/100 mL), cassia (Cinnamomum aromaticum syn. C. cassia, Lauraceae; 2.0 mg), calcium (2.9 mg), sodium (1.1 mg), and potassium (0.9 mg). Cyclists received 3 mL/kg body weight of the herbal drink or the same amount of placebo (colored water) every 20 minutes during bouts of exercise. Cycling time before exhaustion was longer for the active group, but not significantly so. Researchers concluded that both the herbal drink and water acted ergogenically in this study. In another study, 12 recreational athletes took two capsules (150 mg) of Tongkat Ali or placebo daily for seven days. No difference was found between the groups in endurance, running performance, or physiological responses. Other researchers, with a longer study time of five weeks and a dose of 100 mg per day, reported that Tongkat Ali can increase fat-free mass, muscle strength, and muscle size. [Note: The review incorrectly states 150 mg.] In addition, it is suggested that the aphrodisiac effects of Tongkat Ali may be due to stimulation of androgen production. Androgen, the main male sex hormone, is responsible for testosterone production; however, the use of testosterone supplements in organized sports is forbidden. In another study, 13 male recreational athletes took 400 mg of Tongkat Ali or placebo daily for six weeks and it was reported that the urinary testosterone level of those in the active group remained below the cutoff point of the International Olympic Committee Medical Commission and that Tongkat Ali caused no adverse effects on subjects’ liver and kidney functions. It is not stated whether this study found any performance benefits for Tongkat Ali supplementation.
Another clinical study evaluated the effects of Tongkat Ali supplementation (200 mg) vs. placebo on stress hormones and mood in 63 subjects. At four weeks, the active group showed significant improvements, with decreased tension, anger, and confusion, as well as in stress marker profiles, with reduced cortisol and increased testosterone levels.
Tongkat Ali’s effects on endurance and energy use are more pronounced at higher doses and with longer supplementation times. Future studies should examine its effects on mood more closely to determine if the herb’s ergogenic effects are mediated by improvements in mood.
An appended table lists several other herbs studied or used for anti-fatigue, antistress, and endurance-enhancing effects, but it is by no means exhaustive, and these herbs are not discussed.
Khanijo T, Jiraungkoorskul W. Review ergogenic effect of long jack, Eurycoma longifolia. Pharmacogn Rev. July-December 2016;10(20):139-142.