Tongkat Ali: What It Is and How It Works
Tongkat ali, also called longjack or Eurycoma longifolia, is a Southeast Asian root that has moved from traditional medicine into the shelves of sports and "men's health" supplements. It is marketed mainly as a natural testosterone support. Our editors looked at where the plant comes from, which compounds are thought to be active, what controlled trials actually report and where the caveats lie.
Origins and traditional use
Eurycoma longifolia is a slender shrub-like tree native to the rainforests of Malaysia, Indonesia, Thailand and Vietnam. The part used is the root, which is intensely bitter — hence local names that translate roughly as "the bitter one". In traditional practice, root decoctions were taken for fever, fatigue and as a male tonic.
Malaysia in particular has invested in research and standardisation of tongkat ali, and much of the clinical literature comes from collaborations involving Malaysian institutions. A water-extracted, standardised extract has been used in a large share of human trials.
In the UK the product is sold as a food supplement rather than a licensed medicine. That puts responsibility for safety and correct labelling on the business placing it on the market, and it means health claims about testosterone are not authorised.
A review by Bhat and Karim summarised the ethnobotany and pharmacology of the plant and highlighted how variable products can be depending on root age, extraction method and the part of the plant used.
Active compounds and proposed mechanisms
The root contains several classes of compounds. The most studied are quassinoids, such as eurycomanone, along with glycoproteins, alkaloids and polysaccharides. Commercial extracts are often standardised to eurycomanone or to a percentage of "bioactive glycoproteins".
Proposed mechanisms remain partly speculative. Laboratory work suggests eurycomanone may influence steroidogenesis in the testes, possibly by affecting the enzymes that convert testosterone to oestrogen or by modulating feedback signals. Other hypotheses focus on lowering the amount of testosterone bound to sex hormone-binding globulin (SHBG).
A second strand of research looks at stress physiology. Talbott and colleagues reported that a standardised extract reduced salivary cortisol and improved mood scores in moderately stressed adults over four weeks, with a modest rise in salivary testosterone.
It is important to stress that animal and cell findings cannot simply be scaled to humans, and most human trials are small and frequently funded by extract manufacturers.
- Quassinoids (e.g. eurycomanone) — the main marker compounds used for standardisation.
- Glycoproteins and polysaccharides — present in water extracts; their role is less clear.
- Alkaloids — present in small amounts; mostly studied in the laboratory.
What human trials report
The most consistent signal comes from men with low or borderline testosterone. In a study by Tambi and colleagues, men with late-onset hypogonadism taking 200 mg/day of a standardised extract showed a rise in serum testosterone over one month. Henkel and co-workers reported improvements in hormone levels and grip strength in physically active older men and women.
A meta-analysis by Leisegang and colleagues pooled the available trials and found a statistically significant increase in total testosterone, with larger effects in men with hypogonadism than in healthy men with normal levels.
For young, healthy, normally trained athletes, the picture is much weaker. Any increase seems to stay within the normal physiological range and is far smaller than what is produced by pharmaceutical testosterone. There is no robust evidence that tongkat ali alone produces meaningful gains in muscle mass in this group.
Most trials used doses of roughly 200–400 mg/day of standardised extract for 4–12 weeks. Longer-term data are limited.
| Population | Typical trial finding | Confidence |
|---|---|---|
| Men with late-onset hypogonadism | Rise in total testosterone | Moderate; small trials |
| Moderately stressed adults | Lower cortisol, better mood scores | Low to moderate |
| Healthy trained young men | Little or no clear effect | Low |
| Older active adults | Some improvement in strength and hormones | Low; pilot data |
Safety, quality and legal considerations
In published trials of standardised extracts, side effects were infrequent and generally mild: restlessness, sleep disturbance and occasional digestive upset. Laboratory markers of liver and kidney function were usually reported as unchanged over short study periods.
The bigger concern is product quality. Testing of herbal products from various markets has repeatedly found heavy metal contamination and, in some cases, undeclared pharmaceutical ingredients such as erectile dysfunction drugs. Cheap "longjack" products bought online without third-party testing carry a real risk.
Tongkat ali is not on the World Anti-Doping Agency (WADA) Prohibited List, but tested athletes are strictly liable for anything in their sample. Contamination with steroids or stimulants could lead to an anti-doping rule violation, so batch-tested products are the only sensible option for competitive sport.
People with hormone-sensitive cancers, prostate disease, heart conditions or those taking medicines that affect hormones or blood pressure should not use tongkat ali without medical advice. It is not appropriate in pregnancy, breastfeeding or for under-18s.
Editorial conclusions
Tongkat ali is a traditional root with a modest but genuine evidence base, mainly for men whose testosterone is already low and for perceived stress. It is not a natural substitute for hormone therapy and will not turn a normal hormonal profile into an anabolic one.
If someone suspects low testosterone, the first step should be a blood test and a GP appointment rather than a supplement, because symptoms like fatigue and low libido have many possible causes.
For those who choose to try it, standardised extracts at the doses used in research and products with independent testing are the most defensible choice.
You may also find our articles on natural testosterone boosters, on reading a male hormone blood panel and on ashwagandha for stress useful.
References
- Bhat R, Karim AA. Tongkat Ali (Eurycoma longifolia Jack): a review on its ethnobotany and pharmacological importance. Fitoterapia. 2010;81(7):669–679.
- Tambi MI, Imran MK, Henkel RR. Standardised water-soluble extract of Eurycoma longifolia, Tongkat ali, as testosterone booster for managing men with late-onset hypogonadism? Andrologia. 2012;44 Suppl 1:226–230.
- Talbott SM, Talbott JA, George A, Pugh M. Effect of Tongkat Ali on stress hormones and psychological mood state in moderately stressed subjects. J Int Soc Sports Nutr. 2013;10(1):28.
- Henkel RR, Wang R, Bassett SH, et al. Tongkat Ali as a potential herbal supplement for physically active male and female seniors — a pilot study. Phytother Res. 2014;28(4):544–550.
- Leisegang K, Finelli R, Sikka S, Panner Selvam MK. Eurycoma longifolia (Jack) improves serum total testosterone in men: a systematic review and meta-analysis of clinical trials. Medicina (Kaunas). 2022;58(8):1047.
- Maughan RJ, Burke LM, Dvorak J, et al. IOC consensus statement: dietary supplements and the high-performance athlete. Br J Sports Med. 2018;52(7):439–455.
