⚠ Evidence warning: Clinical trials or other evidence do not support the claim that tongkat ali may do very little in healthy young men. This page keeps it as a report of what people, websites or other media say.

Tongkat Ali (Eurycoma longifolia)

Tongkat Ali — scientific infographic poster

Tongkat ali is the bitter taproot of Eurycoma longifolia, a slender understory tree of the Malaysian and Indonesian rainforest, and it is probably the best-known traditional medicine to come out of Malaysia. It is sold worldwide for testosterone, libido, male fertility and stress, and unlike most herbs in that market it does have real randomised human trials behind it — but they are small, short, use different extracts at different doses, and several were funded by companies that sell the ingredient. The honest summary is that something may be there and it is not yet pinned down.

Two practical warnings belong at the very top, because they matter more to most buyers than any question about efficacy. First, Malaysian tongkat ali products have repeatedly been found contaminated with mercury and lead at levels above permitted limits. Second, this is one of the herbal categories where deliberate adulteration with actual pharmaceuticals — sildenafil analogues and related compounds — is a documented problem. What is inside a tongkat ali capsule is a genuine open question, and it is a bigger risk than the plant itself.

Table of Contents

  1. Overview
  2. Names and Identification
  3. Contamination and Adulteration: The Biggest Real Risk
  4. Traditional Use
  5. Active Compounds
  6. Testosterone in Ageing Men
  7. Male Fertility and Semen Quality
  8. Stress, Mood and Cortisol
  9. Strength, Body Composition and Athletes
  10. Forms and Preparations
  11. Dosage
  12. Cautions and Contraindications
  13. Key Research Papers
  14. Connections
  15. Featured Videos

Overview

Eurycoma longifolia Jack is a small, slow-growing tree in the family Simaroubaceae — the quassia family, a group defined chemically by intensely bitter compounds. It grows in the sandy, acid, well-drained soils of lowland rainforest in Peninsular Malaysia, Borneo, Sumatra, southern Thailand, Vietnam, Laos and Cambodia, usually as a spindly understory plant three to ten metres tall with a single unbranched stem and a crown of long compound leaves. It looks unremarkable. What people want is underground.

The medicinal part is the taproot: a long, straight, pale root that plunges almost vertically into the soil. The Malay name — tongkat Ali, "Ali's walking stick" — most likely describes that root's shape, although a folk reading connecting it to male vigour has followed the plant into every marketing brochure ever written about it. The root is harvested by digging the whole tree out, which kills it, and a root worth harvesting takes roughly four years and more usually eight to ten to reach useful size. That single fact explains most of what has gone wrong with the supply chain: wild harvest pressure has been heavy for decades, good roots are expensive, and expensive raw material attracts substitution and dilution. Malaysia has invested substantially in cultivating the plant on plantations and in developing standardised extracts precisely to get out of that trap.

The traditional preparation is a water decoction — thin slices of root boiled for a long time and drunk, or sold as a bundle of root chips with instructions to boil them. The taste is famously, memorably bitter, in the same league as gentian or quinine. In Malaysia the root also reaches people as an ingredient in instant coffee sachets and canned drinks, which is a modern retail format rather than a traditional one, and, as discussed below, historically one of the formats most likely to be adulterated.

Names and Identification

Binomial: Eurycoma longifolia Jack. Family: Simaroubaceae.

The name is shared with at least one entirely different plant, and this matters. In the Malaysian market, "tongkat ali" is sold in colour grades:

If a product does not print the binomial Eurycoma longifolia on the label, you do not know which plant you have bought. That is not a pedantic point — it is the difference between a substance with several randomised trials and a substance with none.

Contamination and Adulteration: The Biggest Real Risk

Most herb pages put safety at the bottom. For tongkat ali it has to come near the top, because the documented problems are with the products rather than with the plant, and they are not hypothetical.

Heavy metals. Ang Hooi Hoon and colleagues at Universiti Sains Malaysia ran a long series of surveys of Malaysian herbal preparations through the 2000s. In one study of 100 tongkat ali preparations on the Malaysian market (2004), samples were analysed for mercury by cold-vapour atomic absorption spectrophotometry and 36% contained 0.52 to 5.30 parts per million (ppm), above the Malaysian limit for mercury in traditional medicines of 0.5 ppm; the authors added that even the products that passed could not be assumed free of mercury, because of batch-to-batch inconsistency. A second survey (2006), of 100 tongkat ali hitam preparations, found 26% at 0.53 to 2.35 ppm. The same research group published parallel findings for lead and arsenic across the broader Malaysian herbal market. Heavy metals do not come from the plant's own metabolism; they come from contaminated soil, from processing equipment, from adulterants deliberately added as fillers or colourants, and from traditional formulations that historically included mineral ingredients. The practical consequence is that contamination is checked with a lot-specific, third-party heavy-metal certificate of analysis — not a general "quality tested" claim on the bottle, but an actual report for that batch showing lead, mercury, arsenic and cadmium in parts per million.

Pharmaceutical adulteration. Products sold for sexual performance are, across every regulatory jurisdiction that has looked, the herbal category most often spiked with real drugs. Said and colleagues published a screening method specifically because sildenafil analogues were turning up in Eurycoma longifolia products — that is, products marketed as a natural alternative to erectile-dysfunction medication were in some cases simply erectile-dysfunction medication in a capsule with a leaf on the label. The analogues used are often modified versions of sildenafil or tadalafil that evade routine screening but retain the pharmacology, including the pharmacology that can drop blood pressure dangerously in someone taking nitrates for angina. A man who avoids his cardiologist's prescription because he prefers "something natural", and then takes an adulterated capsule, has combined the worst of both worlds.

Neither of these is an argument that the herb is dangerous. They are an argument that the supply chain is the risk, and that sourcing matters more than dosing does.

Traditional Use

In Malay traditional medicine tongkat ali was a broad tonic rather than a narrow sexual remedy. Root decoctions were given for fever — including as a malaria remedy across the region — and for dysentery, jaundice, aches, ulcers, boils, wounds, high blood pressure and general fatigue and post-illness weakness. The penawar pahit name, "bitter antidote", reflects a use as an all-purpose counteragent to poisons and unwellness. In Indonesian jamu practice pasak bumi occupies the same broad tonic position, and in Vietnamese thuốc nam the name cây bá bệnh literally advertises the same generality.

Use as a male aphrodisiac and postpartum tonic is real and long-standing, but it is one strand of a much wider traditional profile, and the modern global framing of tongkat ali as essentially a testosterone product is a marketing narrowing rather than a faithful reading of the tradition. The antimalarial use, interestingly, is the one with the clearest chemical rationale: the quassinoids in the root have measurable activity against Plasmodium falciparum in laboratory assays. That is not a recommendation — malaria is a medical emergency treated with artemisinin combination therapy — but it is a reminder that traditional users were not simply guessing.

Traditional use tells us where to look. It is history, not evidence of effect.

Active Compounds

The root contains several structurally distinct groups of compounds, and the arguments about which one matters are not settled.

What standardisation means on a label. Most reputable products state a eurycomanone percentage, commonly somewhere around one to two percent, or state a water-extract ratio such as 100:1 or 200:1. Neither number tells you as much as it appears to. A ratio describes how much raw root went in, not how much of anything active came out, and different manufacturers calculate ratios differently. A eurycomanone percentage is more meaningful, but eurycomanone may not be the constituent responsible for the hormonal effects at all — if the eurypeptide hypothesis is right, a highly concentrated eurycomanone extract could in principle be further from the tested preparations than a plain water extract. This is exactly why "tongkat ali" as a category is so hard to reason about: the trials tested specific extracts, and the retail shelf sells dozens of different ones under one name.

Testosterone in Ageing Men

Proposed mechanism. Three ideas circulate. The first is that the extract raises free testosterone by loosening the grip of sex hormone-binding globulin, which normally holds most circulating testosterone in an inactive form — the analogy usually offered is releasing money from a locked account rather than earning more of it. The second is that it supports steroidogenesis directly in the Leydig cells of the testis. The third is that it lowers cortisol, and since cortisol and testosterone tend to move in opposite directions under stress, lowering one lifts the other. None of these has been demonstrated convincingly in humans. They are hypotheses that fit the observations, and more than one of them may be partly right.

Human evidence. This is the most-studied claim and it is worth being precise about what exists.

A 2022 systematic review and meta-analysis by Leisegang and colleagues pooled the available clinical trials and concluded that Eurycoma longifolia supplementation increased serum total testosterone in men. That is the strongest single statement anyone can currently make in the herb's favour, and it is a real one. But a meta-analysis inherits the weaknesses of its inputs, and the inputs here are a small number of trials that differ in extract, dose, duration and — crucially — in the men studied. Pooling a trial in hypogonadal 60-year-olds with a trial in healthy 25-year-olds produces an average that describes neither.

Chinnappan and colleagues ran a randomised, double-blind, placebo-controlled multicentre trial of a standardised aqueous root extract in ageing men, reporting effects on testosterone and quality-of-life measures. Tambi and colleagues had earlier reported that a standardised water-soluble extract raised testosterone in men with late-onset hypogonadism — one of the most-cited results in the whole literature, and also a small one that is routinely cited far beyond what its size supports. Leitão and colleagues ran what is, at six months, the longest and one of the more rigorous trials: a double-blind, placebo-controlled randomised study of tongkat ali combined with concurrent exercise training in ageing men with androgen deficiency. Testing a supplement on top of an intervention as powerful as structured resistance training is a demanding design, and it is the most informative single trial to look up.

Chan and colleagues tested the herb in young, healthy men — 32 men averaging 24 years of age, given 600 mg a day or placebo for two weeks — and found changes in testosterone, free testosterone and estradiol in favour of the treatment group, with no change in luteinising hormone, follicle-stimulating hormone or sex hormone-binding globulin. That matters because most of the other positive trials were in older, stressed or hypogonadal men; it is also a small, two-week study. A compound that helps a struggling system may do very little in a healthy one, and the burden of proof for the twenty-five-year-old buying it at a gym is different from the burden for the sixty-year-old with a documented low reading.

What weighs against all of it. No individual trial is large; several enrolled fewer than a hundred people and many ran four to twelve weeks. Several of the positive trials tested one patented standardised water extract with the support of the company that manufactures it. That is disclosed openly in the papers rather than hidden, and industry funding does not make a result false — but it is a reason to want independent replication before treating the effect as established. And a change in a blood testosterone number is not the same as a change in how someone feels or functions; the trials that measured symptoms and quality of life alongside hormones are the ones worth reading closely.

Male Fertility and Semen Quality

Proposed mechanism. Whatever supports testosterone production in the testis would also be expected to support spermatogenesis, and several of the root's constituents show antioxidant activity in laboratory assays — relevant because oxidative damage to sperm DNA is one recognised contributor to idiopathic male infertility.

Human evidence. Tambi and Imran reported improvements in semen parameters in men with idiopathic infertility taking a standardised extract. It is a genuinely interesting result and it is the main basis for the fertility claim. It is also a single small study, and semen parameters are notoriously variable within the same man from month to month — sperm concentration can swing widely with a fever, a hot bath, a stressful quarter at work, or simply the interval since the last ejaculation. That variability is exactly why uncontrolled improvements in semen numbers are weak evidence, and it is why this result needs replication in a larger placebo-controlled trial before it can be treated as established.

Most of the remaining fertility literature is in rats. Rodent studies consistently report increases in sperm count and testosterone with Eurycoma extracts, which is why the hypothesis is taken seriously, but rodent reproductive physiology is not a reliable guide to human outcomes and the doses used are frequently far higher than anything a person takes.

The practical framing. Male-factor infertility is diagnosable. A semen analysis costs relatively little and is available through any fertility clinic and most primary-care referrals. The usual fertility work-up is a semen analysis and a hormone panel, followed by a search for treatable causes — varicocele, thyroid disease, medication effects, obesity, heavy alcohol use, anabolic steroid history. A herb with one small supporting study can sit alongside that work-up but does not replace it, and the months spent finding out are months that matter when age is a factor.

Stress, Mood and Cortisol

Proposed mechanism. Tongkat ali is often described as an adaptogen, meaning a substance claimed to buffer the body's stress response rather than stimulate or sedate it. The specific proposal here is modulation of the hypothalamic–pituitary–adrenal axis, with a resulting fall in cortisol.

Human evidence. Talbott and colleagues gave a standardised extract to moderately stressed adults for four weeks and reported reductions in salivary cortisol alongside improvements in mood scores — the tension, anger and confusion subscales of a standard mood inventory. This trial is small and short, but its design is a sensible one: it recruited people who were actually stressed, rather than healthy volunteers with nothing to improve, and it measured a hormone and a symptom together. George and colleagues later ran a 24-week randomised placebo-controlled trial in 93 adults of a water extract combined with multivitamins, again looking at quality of life, mood and stress; overall it found no significant differences between the groups, only improvements within each group over time (two between-group differences appeared in age subgroups). The combination design is a further limitation — when a product contains a herb and a multivitamin, the herb has not been isolated.

Interest in this application has since widened beyond men: a registered randomised trial protocol has been published for a standardised water extract in perimenopausal and postmenopausal women, which is a notable direction of travel for a herb with such a strongly male marketing identity.

Overall the stress evidence is thinner than the testosterone evidence, and the two claims are not independent — if the cortisol effect is real, it may be the mechanism behind the hormone effect rather than a separate benefit.

Strength, Body Composition and Athletes

Proposed mechanism. If testosterone rises, muscle protein synthesis and training adaptation should follow. This is the reasoning behind tongkat ali's presence in a large share of the sports-supplement market.

Human evidence. Chen and colleagues combined Eurycoma longifolia supplementation with resistance training and measured isokinetic muscular strength and power. Kreipke and colleagues tested a multi-ingredient performance supplement containing tongkat ali among other components over four weeks, looking at strength, body composition and anabolic hormones — and multi-ingredient trials, whatever they find, cannot tell you which ingredient did it. The Leitão six-month trial discussed above also sits in this space, because it paired the herb with structured training.

The honest read. The training itself is doing the overwhelming majority of the work in every one of these studies. There is no human trial showing that tongkat ali produces meaningful strength or lean-mass gains on its own, and the effect sizes involved — even taking the hormone findings at face value — are nowhere near what an actual anabolic steroid does. Anyone whose mental model is "natural steroid" has the wrong model.

Athletes subject to drug testing have an additional problem. Tongkat ali itself is not a prohibited substance, but the sexual-performance and testosterone-booster shelf is one of the most heavily adulterated in the supplement industry, and an athlete who tests positive because of an undeclared steroid or steroid precursor in a capsule bears the consequence regardless of intent. Third-party sport-certification programmes exist to test supplements for substances banned in sport.

Forms and Preparations

Reading a label, in order of importance: the binomial Eurycoma longifolia (not just "tongkat ali"); a lot-specific third-party certificate of analysis covering heavy metals; a stated standardisation; and a country of manufacture with a functioning regulator. A product that satisfies all four costs more. It is the one part of this decision where paying more genuinely buys something.

Dosage

There is no established therapeutic dose, no official monograph dose, and no dose–response study adequate to define one. What follows is a description of what the trials used, not a recommendation.

The trials gave the herb for a defined period and measured something before and after. For testosterone, that measurement is a blood testosterone level taken before starting and again at the end of the period. Without a before-and-after measurement there is no way to tell whether a hormone-active herb is doing anything, and taking one indefinitely is how people spend years and hundreds of dollars on a product that was never doing anything for them.

Cautions and Contraindications

Product contamination is the leading risk. Mercury and lead above regulatory limits have been documented repeatedly in Malaysian tongkat ali preparations, and sildenafil analogues have been documented in Eurycoma products. Both facts bear on where a product comes from far more than on how much is taken. A product from an unbranded market stall, an anonymous online seller, or any source that cannot produce a lot-specific heavy-metal analysis comes with no information about either risk, and coffee and drink sachets are the format historically most associated with pharmaceutical adulteration.

Hormone-sensitive conditions. Prostate tissue grows under the influence of testosterone, and the standard hormone treatment for prostate cancer works by lowering it, so a supplement marketed for raising testosterone raises a concern for anyone with prostate cancer, a history of prostate cancer, an enlarged prostate (benign prostatic hyperplasia) with significant symptoms, or a raised prostate-specific antigen (PSA). The same concern applies to men on testosterone replacement therapy — adding an unmeasured hormone-active herb to a monitored hormone protocol makes the monitoring meaningless. Because oestrogenic and anti-oestrogenic activities have both been reported for Eurycoma constituents in laboratory work, the same theoretical concern extends to women with hormone-sensitive breast or uterine conditions.

Immunosuppressant therapy. Laboratory work reports immunostimulant activity for several Eurycoma constituents. That raises a theoretical concern for anyone taking immunosuppressive medication — after a transplant, or for an autoimmune disease — because a substance that may push the immune system in the opposite direction to the prescription could work against it; in the 24-week George trial of a water extract with multivitamins, lymphocyte (white blood cell) counts rose in the active group.

Pregnancy and breastfeeding. There is no safety data: safety in human pregnancy and breastfeeding is entirely unstudied, quassinoids are biologically active compounds with reported effects on reproductive tissue in animal studies, and mercury and lead, the contaminants described above, are a recognised hazard to a developing baby.

Children and adolescents. There is no safety data in children or adolescents, and a herb marketed for raising testosterone is aimed at the same hormone system that drives puberty and growth.

Drug interactions. Formal human interaction studies are lacking. The possible interactions raised are with: anticoagulants and antiplatelet drugs (some constituents affect platelet function in laboratory assays); antidiabetic drugs, since blood-glucose-lowering effects have been reported in animals and additive effects could cause hypoglycaemia; antihypertensives, for the same additive reason; and propranolol, for which reduced absorption has been reported. Any product adulterated with a sildenafil analogue would interact catastrophically with nitrates — nitroglycerin, isosorbide — which is a further reason to treat sourcing as a safety issue rather than a quality preference.

Liver and kidney disease. In a rat study of a commercial tongkat ali-infused coffee (2020), organ tissues looked normal under the microscope, but blood tests showed raised kidney markers in both sexes at 0.29 g/kg body weight, raised liver and blood-fat markers in some female groups on long-term dosing, and lower platelet counts in treated males; the authors saw no dose pattern and set the no-observed-adverse-effect level at 1 g/kg. In a 28-day rat study of a combined Eurycoma and Labisia pumila formulation (2021), blood tests showed no significant toxicity at any dose, but some organs showed microscopic changes at the highest dose, 2,000 mg/kg. Neither study covers long-term human use, and how the body clears the herb's constituents has not been worked out — a gap that matters most for people with existing liver or kidney disease.

Reported side effects. In the trials, adverse events were generally mild and comparable to placebo: insomnia and restlessness (which is why it is usually taken in the morning), irritability, and gastrointestinal upset. Some users report an increase in body odour. The bitterness itself is enough to stop some people.

Key Research Papers

  1. Leisegang K, Finelli R, Sikka SC, et al. Eurycoma longifolia (Jack) improves serum total testosterone in men: a systematic review and meta-analysis of clinical trials. Medicina (Kaunas). 2022;58(8). — PubMed PMID: 36013514
  2. Leitão AE, Vieira MCS, Pelegrini A, et al. A 6-month, double-blind, placebo-controlled, randomized trial to evaluate the effect of Eurycoma longifolia (Tongkat Ali) and concurrent training on erectile function and testosterone levels in androgen deficiency of aging males (ADAM). Maturitas. 2021;145:78–85. — PubMed PMID: 33541567
  3. Chinnappan SM, George A, Pandey P, et al. Effect of Eurycoma longifolia standardised aqueous root extract–Physta on testosterone levels and quality of life in ageing male subjects: a randomised, double-blind, placebo-controlled multicentre study. Food and Nutrition Research. 2021;65. — PubMed PMID: 34262417
  4. Chan KQ, Stewart C, Chester N, et al. The effect of Eurycoma longifolia on the regulation of reproductive hormones in young males. Andrologia. 2021;53(4):e14001. — PubMed PMID: 33559971
  5. 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. — PubMed PMID: 21671978
  6. Tambi MI, Imran MK. Eurycoma longifolia Jack in managing idiopathic male infertility. Asian Journal of Andrology. 2010;12(3):376–380. — PubMed PMID: 20348942
  7. Talbott SM, Talbott JA, George A, et al. Effect of Tongkat Ali on stress hormones and psychological mood state in moderately stressed subjects. Journal of the International Society of Sports Nutrition. 2013;10(1):28. — PubMed PMID: 23705671
  8. George A, Udani J, Abidin NZ, et al. Efficacy and safety of Eurycoma longifolia (Physta) water extract plus multivitamins on quality of life, mood and stress: a randomized placebo-controlled and parallel study. Food and Nutrition Research. 2018;62. — PubMed PMID: 30574050
  9. Ang HH, Lee EL, Cheang HS. Determination of mercury by cold vapor atomic absorption spectrophotometer in Tongkat Ali preparations obtained in Malaysia. International Journal of Toxicology. 2004;23(1):65–71. — PubMed PMID: 15162849
  10. Ang HH, Lee KL. Contamination of mercury in tongkat Ali hitam herbal preparations. Food and Chemical Toxicology. 2006;44(8):1245–1250. — PubMed PMID: 16567029
  11. Said MM, Gibbons S, Moffat AC, et al. Rapid detection of sildenafil analogue in Eurycoma longifolia products using a new two-tier procedure of the near infrared (NIR) spectra database. Food Chemistry. 2014;158:296–301. — PubMed PMID: 24731345
  12. Rehman SU, Choe K, Yoo HH. Review on a traditional herbal medicine, Eurycoma longifolia Jack (Tongkat Ali): its traditional uses, chemistry, evidence-based pharmacology and toxicology. Molecules. 2016;21(3):331. — PubMed PMID: 26978330
  13. Bhat R, Karim AA. Tongkat Ali (Eurycoma longifolia Jack): a review on its ethnobotany and pharmacological importance. Fitoterapia. 2010;81(7):669–679. — PubMed PMID: 20434529
  14. Ahmad N, Teh BP, Halim SZ, et al. Eurycoma longifolia-infused coffee — an oral toxicity study. Nutrients. 2020;12(10). — PubMed PMID: 33066137
  15. Teh BP, Ahmad N, Ibnu Rasid EN, et al. Herbal-based formulation containing Eurycoma longifolia and Labisia pumila aqueous extracts: safe for consumption? Pharmaceuticals (Basel). 2021;14(2). — PubMed PMID: 33579048

PubMed Topic Searches

  1. PubMed: Eurycoma longifolia — randomised controlled trials
  2. PubMed: Eurycoma longifolia and testosterone
  3. PubMed: Eurycomanone — pharmacology
  4. PubMed: Tongkat ali — lead and arsenic contamination
  5. PubMed: Herbal supplement adulteration with sildenafil analogues
  6. PubMed: Eurycoma longifolia — male infertility and semen quality
  7. PubMed: Eurycoma longifolia — toxicity studies
  8. PubMed: Eurycoma longifolia — antimalarial activity
  9. PubMed: Polyalthia bullata — "black tongkat ali"
  10. PubMed: Eurycoma longifolia — exercise performance

Connections

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