Tongkat Ali (Eurycoma longifolia): Clinical Evidence for Testosterone, Libido, and Stress

This article is for educational and research purposes only and does not constitute medical advice. Tongkat Ali is a supplement, not a medicine. Consult a qualified healthcare practitioner before use, especially if there is a history of hormone-sensitive conditions, cardiovascular concerns, or current prescription medication use.

Tongkat Ali is one of the better-evidenced botanical interventions for male testosterone — but the evidence base is narrower than marketing material often suggests. Of the dozens of botanicals promoted for hormonal support across Australian and international supplement markets, Eurycoma longifolia has accumulated a comparatively serious clinical trial portfolio over the past two decades. Yet the literature also reveals a more disciplined picture than the headline claims: meaningful effects in specific populations, smaller or null effects in others, and a clear distinction between standardised extracts with reproducible activity and the bulk powder products that dominate cheaper retail channels.

This review covers what the human trial data actually demonstrate, how the active compounds appear to work, which extract formats have been studied, and where the gaps remain — including the often-overlooked contamination risks associated with non-standardised material.

---

What Tongkat Ali Is

Tongkat Ali (Eurycoma longifolia Jack) is a slender flowering shrub native to the rainforests of Malaysia, Indonesia, Vietnam, and southern Thailand. Within the Simaroubaceae family, it grows to roughly 10 metres in height, though commercial preparations focus almost exclusively on the long, tapered root system — the part of the plant where the characteristic bioactive constituents accumulate at the highest concentrations.

In Malay traditional medicine the plant is most commonly called Tongkat Ali, often translated as "Ali's walking stick" — a reference both to its slender form and its traditional reputation for vitality. Indonesian usage favours Pasak Bumi, meaning "stake of the earth," while Vietnamese references describe it as cay ba binh, "the tree that cures a hundred diseases." Traditional preparations used the root as a decoction or boiled tonic, taken for fatigue, fever, low libido, and post-illness recovery. The leaf, bark, and fruit have minor traditional applications but are not the basis of any commercially relevant modern extract.

The choice of plant part matters. Root concentration of the relevant bioactives is considerably higher than in stems or leaves, and reputable clinical-grade preparations specify root material as the source. Products marketed simply as "Tongkat Ali powder" without root specification are not directly comparable to the standardised extracts used in clinical trials.

Active Constituents: What Is Actually in the Root

The pharmacological complexity of Eurycoma longifolia is one reason early research progressed slowly. The root contains several distinct bioactive classes, each contributing to a different aspect of its observed activity.

Quassinoids are the most studied and pharmacologically distinctive class. Eurycomanone is the lead compound — a highly oxygenated C20 quassinoid that is now the standardisation marker for most reputable extracts. Related quassinoids include 13α(21)-epoxyeurycomanone, eurycomalactone, and eurycomanol. Quassinoids contribute to the bitter taste characteristic of the root and are believed to be the primary drivers of the steroidogenic effects observed in cell and animal models.

Squalene derivatives, including 14,15β-dihydroxyklaineanone and related triterpenoids, contribute to lipid-soluble bioactivity and may support membrane-level interactions with steroidogenic enzymes.

Biphenylneolignans such as 2,2'-dimethoxy-4-(3-hydroxy-1-propenyl)-4'-(1,2,3-trihydroxypropyl) diphenyl ether have demonstrated cytotoxic activity in preclinical assays — relevant to broader pharmacology research, though less central to the testosterone literature.

Glycosaponins, a structurally diverse class of triterpenoid glycosides, are often co-standardised in commercial extracts because they contribute to the water-soluble fraction that captures the historical preparation method (decoction in hot water).

A typical clinical-grade extract specifies eurycomanone (usually a minimum of 0.8% to 2.0%), total quassinoids, and glycosaponins (often 40% or higher). Products that list only "Tongkat Ali extract" without quantification of these markers cannot be evaluated against the trial literature.

Standardised Extracts: Physta® and LJ100®, and Why Standardisation Matters

Two branded extracts dominate the credible clinical evidence base.

Physta® (Biotropics Malaysia) is a hot-water root extract developed in collaboration with the Malaysian Ministry of Science, Technology and Innovation and the U.S. National Cancer Institute under an early bioprospecting agreement. It is standardised to a minimum of 22% glycosaponins, 30% polysaccharides, and 0.8 to 1.5% eurycomanone. The majority of randomised controlled trials examining stress, cortisol, and testosterone outcomes — including the Tambi, Talbott, and several Henkel papers — used Physta® or its predecessor research-grade extract.

LJ100® (HP Ingredients) is a hot-water extract concentrated and partially hydrolysed to yield a higher proportion of small-molecule bioactives. Marketing material historically referenced a "100:1" extract ratio, though modern standardisation focuses on bioactive quantification — typically 22% bioactive eurypeptides and 40% glycosaponins. LJ100® has been used in several published trials, particularly those exploring resistance training and athletic recovery endpoints.

The case for standardisation is not academic. Raw or non-standardised Tongkat Ali products show wide variability in eurycomanone content — some commercial samples have been shown to contain <5% of the eurycomanone present in clinical-grade extracts when independently assayed. Without compound-level standardisation, dose statements (such as 400 mg/day) are essentially meaningless because the active load is unknown. This is also the point at which contamination risk diverges sharply between the two product tiers, discussed later in this article.

Testosterone Evidence in Men

The testosterone literature on Tongkat Ali is best evaluated by separating the studied populations. Effect sizes differ considerably between men with documented low testosterone and those with normal baseline levels.

Late-Onset Hypogonadism

A pilot trial published by Tambi and colleagues in Andrologia (Tambi et al., 2012, Andrologia) examined 76 men aged 36 to 67 years with clinically defined late-onset hypogonadism (LOH), characterised by baseline total testosterone below the lower reference range. Participants received 200 mg/day of a Physta®-style standardised extract for one month. Mean total testosterone increased from approximately 5.66 nmol/L to 8.31 nmol/L — a clinically meaningful shift that moved the majority of participants into the lower normal range. Aging Males Symptoms (AMS) questionnaire scores also improved significantly.

A separate observational study following men with the symptoms of androgen deficiency reported comparable directional findings, though the open-label design limits inferential strength. Across the deficient-baseline population, free testosterone increases in the order of 20% have been observed with standardised extract dosing across four-week to twelve-week windows.

Eugonadal Men

The picture in men with normal baseline testosterone is more conservative. Several smaller trials have examined recreationally active or athletic populations and have found smaller, sometimes non-significant absolute increases in total testosterone. What does appear more consistent across these studies is an increase in free testosterone — the bioavailable fraction — even when total testosterone changes modestly. The mechanism for this disconnect involves sex hormone-binding globulin (SHBG), discussed below.

Resistance-Trained Populations

Henkel and colleagues (Henkel et al., 2014, Phytother Res) examined 13 physically active senior men and women given 400 mg/day of a standardised extract for five weeks. The study reported significant increases in total and free testosterone among the male participants alongside improvements in muscular force, with the effect attributed to a combination of mild steroidogenic support and SHBG modulation. While the sample size was small, the directional finding has been broadly replicated.

The honest summary is that Tongkat Ali appears most effective at restoring testosterone toward the normal range in men with documented deficiency, with smaller and less consistent effects in men whose baseline levels are already within normal range. This pattern — larger response in the deficient, ceiling-bound response in the replete — is common across botanical interventions and should anchor any reading of the literature. Anyone considering a serial measurement approach to evaluating response should review the optimal range framework for testosterone testing before drawing conclusions from a single reading.

SHBG and Free Testosterone: The Mechanism Story

A central pharmacological feature of Tongkat Ali is its apparent ability to displace testosterone from its primary carrier protein, sex hormone-binding globulin (SHBG). SHBG binds approximately 40 to 60% of circulating testosterone with high affinity, leaving only the unbound fraction — typically 1 to 4% — biologically active at the receptor level.

In preclinical work, eurycomanone and related quassinoids have been shown to interact with SHBG-testosterone binding dynamics in a manner that increases the free fraction without necessarily altering total circulating testosterone. This provides a mechanistic explanation for why some trials report meaningful changes in free testosterone, libido, and energy outcomes even when total testosterone shifts are modest.

A complementary mechanism involves direct support of steroidogenesis. Eurycomanone has been observed in cellular models to upregulate CYP17 (17α-hydroxylase/17,20-lyase) activity in Leydig cells, increasing conversion of pregnenolone toward the androgen synthesis pathway, and to inhibit aromatase — the enzyme converting testosterone to estradiol. The combined effect, where present, is a modest tilt of the androgen-estrogen axis in favour of androgens.

These mechanisms are coherent with the clinical observations: larger absolute changes in men starting from a lower endogenous baseline, and SHBG-mediated bioavailability shifts that benefit even those whose total testosterone moves little.

Cortisol and Stress: The Talbott Findings

One of the more frequently cited Tongkat Ali papers examined stress markers rather than testosterone directly. Talbott and colleagues (Talbott et al., 2013, JISSN) conducted a four-week randomised trial in 63 moderately stressed adults — men and women — given 200 mg/day of a Physta®-style standardised extract. Participants reported reductions in tension, anger, and confusion on the validated Profile of Mood States questionnaire, and salivary cortisol concentrations decreased by approximately 16% compared with placebo. Salivary testosterone increased by a comparable percentage in the active group.

The mechanism is plausibly linked to HPA-axis modulation, in line with the adaptogen classification, with eurycomanone and the glycosaponin fraction both implicated. The Talbott data are also the basis for Tongkat Ali's positioning as a dual-axis intervention — affecting both the HPA stress axis and the HPG (hypothalamic-pituitary-gonadal) axis — rather than a single-pathway steroidogenic agent. This dual action is what distinguishes it pharmacologically from compounds such as fenugreek that operate more narrowly.

For context on broader adaptogenic frameworks, the comparison of botanical adaptogens including ashwagandha covers cortisol findings under a similarly disciplined evidence lens.

Female Studies: A Smaller but Real Literature

The framing of Tongkat Ali as exclusively a men's botanical is incomplete. Smaller trials have examined the extract in women, particularly in the context of mood, bone density, and the Talbott stress study (which included female participants and showed comparable mood-related effects across sexes).

Preliminary research has also examined eurycomanone's effects on bone turnover markers in animal models, with some evidence of a beneficial influence on osteoblast activity. Human data here remain limited but warrant attention as the female safety and efficacy literature expands. The published female-inclusive trials have not raised androgenisation concerns at standardised extract doses, though this remains an area where conservative practice — and clinician consultation — applies. The hormonal context for women considering botanical support overlaps substantially with the research on maca for hormonal balance, which has a deeper female-specific evidence base.

Strength, Body Composition, and Recovery

Beyond hormonal endpoints, several trials have examined resistance training and physical performance outcomes. The Henkel paper noted above reported strength improvements in conjunction with hormonal changes. A separate trial in trained men examined lean mass and fat mass changes over five weeks of supervised resistance training, with the active group showing modestly favourable body composition shifts relative to placebo.

The magnitude of these effects is comparable to other botanical interventions — meaningful but not transformative — and is best understood as a small adjunctive contribution to a training and nutrition program rather than as an independent driver of body composition outcomes. The same logic applies to broader physique and hormonal protocols described in research-based weight management approaches for men over 50, where botanical support sits within a structured intervention rather than carrying it.

Sleep and HPG Axis Context

Testosterone synthesis is heavily concentrated in the latter stages of nighttime sleep, with the morning testosterone peak depending on adequate sleep architecture — particularly REM sleep and the early-morning slow-wave sleep windows. Chronic sleep restriction has been shown to reduce daytime testosterone by 10 to 15% in healthy young men within one week of restricted sleep. Any intervention aimed at the HPG axis, including Tongkat Ali, operates within the constraint imposed by sleep status.

This is not a Tongkat Ali finding per se, but it is essential context: the largest treatable variable affecting endogenous testosterone in many adult men is sleep duration and consolidation. A supplement context paper that ignores this risks attributing to a botanical what is in fact a behavioural ceiling. Researchers and individuals evaluating Tongkat Ali response over an eight-to-twelve-week window should hold sleep status reasonably constant to interpret results meaningfully.

Dosing: What the Trials Used

The most commonly studied dosing range for clinical-grade standardised extracts is 200 to 400 mg/day, typically of Physta® or equivalent material standardised to a minimum of 0.8% eurycomanone and 22% glycosaponins.

• 200 mg/day was the Tambi hypogonadism trial dose and the Talbott stress trial dose
• 300 to 400 mg/day has been used in the Henkel-style resistance-trained populations and several body composition trials
• Doses above 600 mg/day of clinical-grade extract are not well studied and offer no clear additional benefit

Time-to-effect is generally reported as two to four weeks for subjective stress and energy markers, with hormonal changes (free testosterone, total testosterone, cortisol) typically measured at four-week, eight-week, or twelve-week endpoints. The 200 mg/day Tambi trial showed measurable change within one month in the deficient-baseline population.

Cycling is a frequently raised topic without strong evidence either way. Most published trials are four to twelve weeks in duration, so longer-term continuous use is empirically under-characterised. A conservative pattern observed in some clinical settings is five days on, two days off, or eight weeks on followed by two to four weeks off, though this is practitioner convention rather than trial-derived protocol.

Dose translation is only meaningful when standardisation is specified. A 400 mg capsule of a non-standardised 1:1 root powder contains a tiny fraction of the eurycomanone in a 200 mg capsule of clinical-grade extract, despite the higher milligram label. Capsule weight is not a valid proxy for active load.

Safety, Contamination, and Heavy Metal Concerns

The safety profile of clinical-grade standardised Tongkat Ali in the published trial literature is generally favourable. Reported adverse events have been minor — mild gastrointestinal effects, occasional insomnia at higher doses, and infrequent restlessness — and short-term safety markers (liver enzymes, renal function, blood pressure) have remained within reference ranges in most trials. Ismail and colleagues conducted a 90-day toxicity assessment in human volunteers using a standardised Physta® extract at clinically relevant doses and reported no significant safety signals across haematological, biochemical, or organ-function markers.

The safety conversation diverges sharply when non-standardised material is considered. Independent surveys of retail Tongkat Ali products — particularly bulk powders sourced from informal supply chains — have repeatedly identified contamination concerns:

• Heavy metals: detectable levels of mercury, lead, and cadmium exceeding food-grade thresholds in a non-trivial proportion of unregulated retail samples
• Microbial contamination: total aerobic counts above pharmacopoeial limits in some unrefrigerated bulk products
• Adulteration: undeclared synthetic compounds, including phosphodiesterase-5 inhibitors, identified in some "Tongkat Ali" products marketed for erectile function

These findings do not reflect the standardised extracts studied in clinical trials. They do reflect the broader retail landscape, particularly for products with no third-party testing certificates, no eurycomanone quantification, and no Australian Therapeutic Goods Administration (TGA) listing. Where Tongkat Ali is purchased, third-party heavy metals testing and identifiable standardised extract sourcing are basic quality controls — not optional reassurances.

Where Tongkat Ali Sits Among Male Hormonal Botanicals

A practical comparison helps situate Tongkat Ali within the broader botanical landscape:

Versus maca (Lepidium meyenii): Maca's mechanism is not hormonal in the classical sense — it does not measurably change testosterone or estradiol in most trials. Its libido and mood effects appear to operate through macamides and dopaminergic modulation. Tongkat Ali, by contrast, has more direct steroidogenic and SHBG-related effects. The two botanicals are not interchangeable.

Versus ashwagandha (Withania somnifera): Ashwagandha has the larger and more diverse evidence base, with significant stress, sleep, and modest testosterone findings — particularly in the Lopresti and Wankhede trials. Tongkat Ali shows comparable cortisol effects in the Talbott data and arguably stronger direct testosterone evidence in deficient populations, though with a smaller overall trial base.

Versus Korean Red Ginseng: Ginseng's research strength lies in erectile function (with substantial RCT evidence), immune function, and cognitive performance, with limited direct testosterone data. Tongkat Ali targets the hormonal axis more directly but has thinner erectile function evidence. The two are mechanistically distinct and are sometimes co-formulated.

Versus fenugreek: Fenugreek extracts standardised to protodioscin (such as Testofen) have a more limited and contested testosterone evidence base, with some null trials. Tongkat Ali has the more reproducible hormonal signal in standardised-extract trials, though both work in part through SHBG modulation.

The honest read is that Tongkat Ali is one of three or four botanicals with credible hormonal evidence in men — alongside ashwagandha for stress-mediated testosterone effects and ginseng for erectile and vascular endpoints — and not a singular outlier above the rest.

Key Takeaways

• The plant: Tongkat Ali is Eurycoma longifolia, root-derived, traditional in Malay and Indonesian medicine, with a substantive but bounded clinical literature
• Active compounds: quassinoids (eurycomanone in particular), squalene derivatives, biphenylneolignans, and glycosaponins
• Standardisation matters: Physta® and LJ100® are the clinically studied formats; non-standardised products are not equivalent and carry contamination risk
• Testosterone effect: largest in men with documented deficiency (around 20% free T increases on Tambi-style protocols), smaller in eugonadal populations
• SHBG and free T: the mechanism story explaining bioavailability effects even when total testosterone changes are modest
• Stress and cortisol: Talbott data show roughly 16% salivary cortisol reductions alongside mood improvements
• Female studies: limited but real, with mood-related findings replicated in mixed-sex trials
• Dosing: 200 to 400 mg/day of clinical-grade standardised extract for 4 to 12 weeks
• Safety: favourable in standardised trials; contamination and adulteration risks attach to non-standardised products
• Positioning: one of several credible male hormonal botanicals, not a unique outlier

---

References

• Tambi, M. I. B. M., Imran, M. K., Henkel, R. R. (2012). Standardised water-soluble extract of Eurycoma longifolia, Tongkat Ali, as testosterone booster for managing men with late-onset hypogonadism? Andrologia, 44(s1), 226–230.
• Henkel, R. R., Wang, R., Bassett, S. H., Chen, T., Liu, N., Zhu, Y., Tambi, M. I. (2014). Tongkat Ali as a potential herbal supplement for physically active male and female seniors — a pilot study. Phytotherapy Research, 28(4), 544–550.
• Talbott, S. M., Talbott, J. A., George, A., Pugh, M. (2013). Effect of Tongkat Ali on stress hormones and psychological mood state in moderately stressed subjects. Journal of the International Society of Sports Nutrition, 10, 28.
• Ismail, S. B., Wan Mohammad, W. M. Z., George, A., Nik Hussain, N. H., Musthapa Kamal, Z. M., Liske, E. (2012). Randomized clinical trial on the use of Physta freeze-dried water extract of Eurycoma longifolia for the improvement of quality of life and sexual well-being in men. Evidence-Based Complementary and Alternative Medicine, 2012, 429268.
• George, A., Henkel, R. (2014). Phytoandrogenic properties of Eurycoma longifolia as natural alternative to testosterone replacement therapy. Andrologia, 46(7), 708–721.
• Rehman, S. U., Choe, K., Yoo, H. H. (2016). Review on a traditional herbal medicine, Eurycoma longifolia Jack (Tongkat Ali): its traditional uses, chemistry, evidence-based pharmacology and toxicology. Molecules, 21(3), 331.