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Tongkat Ali: What the Research Actually Says
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Inertia Supplements

This article covers the published research on Eurycoma longifolia, the plant known as Tongkat Ali. Educational content about the research is ingredient science: it describes what researchers examined, not what any supplement product will do for you. Our licensed claims (NPN 80133495) are stated plainly where they appear. All research citations link to publicly accessible sources. This is not medical advice.

What Tongkat Ali is

Eurycoma longifolia is a slender tree native to the rainforests of Malaysia, Indonesia, and the surrounding region. The root, which the plant takes years to develop, is the part used in supplements. Traditional preparations steeped or boiled the root in water. Modern extracts concentrate the root material through more targeted processes.

The common name “Tongkat Ali” translates roughly to “Ali’s walking stick” in Malay, a reference to the root’s appearance.

In supplement form, you will typically find it sold as a root extract described by a concentration ratio (most commonly 100:1 or 200:1). The ratio tells you how much raw root was used to produce a gram of extract. What is actually in the extract depends on the process, the root quality, and what anyone has tested for. Our full explanation of the ratio is in What 100:1 actually means on a Tongkat Ali label.

What it is licensed to do in Canada

Health Canada has reviewed Eurycoma longifolia and granted NPN 80133495 for our product with three authorized claims. These are the claims the licensing process found substantiated at the studied dose for this formulation:

  1. Eurycoma longifolia helps promote testosterone production.
  2. Helps to enhance resistance training and muscular strength.
  3. Helps support healthy sexual interest.

These are the health claims we are authorized to make. They are stated here plainly with the NPN. Everything else in this article is ingredient science, framed as what researchers examined, kept separate from those licensed claims.

Our product: 600 mg of 100:1 Eurycoma longifolia root extract per capsule. Single-ingredient. NPN 80133495. Third-party lab-tested, every batch.

What the research has examined

The following section describes what researchers studied about Eurycoma longifolia in published trials and reviews. It is ingredient science: it describes what the studies looked at and what they found about the plant, not what our product will do for you. All citations are publicly accessible.

Testosterone, hormones, and men who start lower

The most-discussed area of Tongkat Ali research involves male hormone markers. Here is what the better studies actually show:

Several randomized controlled trials (RCTs) have examined Eurycoma longifolia’s effect on total testosterone in men. The clearest positive signals appear in two specific populations: men with lower baseline testosterone levels (including hypogonadal or late-onset hypogonadism populations), and men in situations of physical or psychological stress.

One frequently cited RCT (Tambi et al., 2012, published in Evidence-Based Complementary and Alternative Medicine) examined 76 men with late-onset hypogonadism who received a standardized water-soluble extract of Eurycoma longifolia for one month. At the end of the study, 90% of subjects showed testosterone levels in the normal range, compared to 35.5% at baseline. This is the study most commonly cited when brands describe Tongkat Ali’s testosterone effects.

It is worth noting what this study was: a single-arm open-label study (no control group) in a population that started with below-normal testosterone. It does not tell us much about effects in men who already have normal testosterone levels.

Studies in healthy men with normal baseline testosterone show more modest or mixed results. A 2003 RCT (Hamzah and Yusof, British Journal of Sports Medicine) in recreational athletes found improvements in muscular force and lean mass alongside hormonal changes with a 100 mg standardized extract. A 2012 paper (Chan et al.) examining a 300 mg water extract in late-middle-aged men showed significant improvements in total testosterone and physical function scores.

The overall picture from the literature:

  • The clearest hormonal effects appear in men with lower baseline levels and in stressed populations.
  • Effects in men with already-normal testosterone levels are less consistent.
  • The mechanism most commonly proposed (inhibition of SHBG reducing testosterone binding) is less supported by the data than often claimed. One double-blinded RCT (Talbott et al., 2013) found no significant between-group SHBG difference despite positive testosterone effects. We mention this because the SHBG mechanism is the one most frequently marketed and the one with the weakest direct support.

Stress and cortisol

One of the better-evidenced areas in Tongkat Ali research is its effect on cortisol, the primary stress hormone.

A double-blind RCT (Talbott et al., 2013, Journal of the International Society of Sports Nutrition) randomized 63 moderately stressed subjects to 200 mg of a standardized Eurycoma longifolia extract or placebo for four weeks. The extract group showed approximately 16% lower salivary cortisol and 37% higher total testosterone compared to baseline, alongside improvements in self-reported tension, anger, and confusion on the Profile of Mood States (POMS) scale.

This is probably the best-designed human trial on Tongkat Ali’s stress-related effects. It is a single study. It uses a specific standardized extract at a specific dose in a moderately stressed population. It should be read as a promising finding about this ingredient in this context, not as a settled conclusion.

It does not authorize us to claim our product lowers your cortisol.

The cortisol research is relevant because it provides a mechanistic explanation for one of the most consistently reported user experiences with this plant: a sense of improved stress resilience, better mood stability, and cleaner energy compared to stimulants. The research examines this in the ingredient.

Resistance training and muscular strength

This is one of our three licensed claims (helps to enhance resistance training and muscular strength, NPN 80133495), so we can state it plainly as a product claim.

The research that underlies this is meaningful. The 2003 Hamzah and Yusof study in recreational athletes used a 100 mg standardized extract over 5 weeks and found significantly greater strength and lean mass gains compared to placebo. Subsequent studies in older adults and general populations have found similar patterns.

The training effect appears most clearly when the supplement is taken consistently alongside actual resistance training. It is not a replacement for the training.

Healthy sexual interest

This is also a licensed claim (helps support healthy sexual interest, NPN 80133495). The research examining libido and sexual function in men has generally been positive in populations where the compound was studied, though most of this literature is in men with lower-than-normal testosterone or in aging male populations. We include the licensed claim here for completeness; it is not the primary reason most supplement buyers in our persona set reach for this product.

What the research does not support

A few common claims about Tongkat Ali are worth addressing directly:

“Natural testosterone replacement” or “natural TRT.” This framing implies the compound can substitute for medical testosterone replacement therapy. The research does not support that characterization, particularly for men without a diagnosed deficiency. We do not use this framing.

“Boosts testosterone by X%.” Percentage claims drawn from specific studies apply to the specific populations and extracts studied, not universally to all users. A claim like “raises testosterone 37%” from the Talbott study applies to moderately stressed adults using a specific extract in that trial. Generalizing percentage outcomes to a general population is misleading.

“Same-day results.” The studied outcomes in the research literature emerge over four to twelve weeks of consistent use. The research does not describe acute, same-day effects comparable to a stimulant.

The SHBG mechanism as the primary explanation. As noted above, the RCT data is mixed on whether Eurycoma longifolia significantly changes SHBG levels. The testosterone effects in the better studies appear despite the SHBG picture being less clear-cut than the mechanism implies.

Honest limitations of the existing evidence

We read the research so you can decide what to make of it. The limitations are worth knowing:

  • Most human trials are small (typically 30–100 subjects) and relatively short (4–12 weeks).
  • Study populations vary significantly (hypogonadal men vs. recreational athletes vs. stressed adults vs. elite athletes), making it hard to generalize across studies.
  • The most-cited studies use specific standardized extracts (Physta, LJ100) at specific doses. Not all Tongkat Ali products use these extracts. The results from those studies do not automatically transfer to products using different extract processes.
  • Publication bias is possible: positive results are more likely to be published and cited.

The responsible read: Eurycoma longifolia has a meaningful human research base for a botanical supplement. The strongest signals are in populations with lower baseline testosterone, in stressed adults, and in the context of resistance training. The evidence is promising and worth taking seriously; it is not definitive in the way pharmaceutical clinical data is.

How to run a fair trial

If you decide to try Tongkat Ali based on the above:

  • Use a single-ingredient product at a specified dose so you know what you are running the trial on.
  • Give it at least four weeks of consistent daily use before drawing conclusions, and eight weeks for a more complete picture.
  • Track something specific: a training metric, energy levels across a week, or sleep quality.
  • Use a product with a Canadian NPN and a batch COA so the formulation is checkable.

Our Tongkat Ali: 600 mg per capsule, 100:1 single-ingredient extract, NPN 80133495, third-party lab-tested. See the full product page and dose breakdown at inertiasupplements.ca.

FAQ

Does Tongkat Ali actually work?

The honest answer is: for some people, in some contexts, the research suggests it does something real. The clearest evidence is in men with lower baseline testosterone, in moderately stressed adults, and in resistance-training populations over 4–12 weeks. In men with normal testosterone who are otherwise healthy, the evidence is more mixed. It is not a universal “yes” or “no.”

What does the research say about the testosterone effect?

The most consistent positive findings come from studies in men with lower-than-normal testosterone or in stressed populations. One 2013 RCT in moderately stressed adults found approximately 16% lower cortisol and 37% higher testosterone compared to baseline with a standardized extract over 4 weeks. A 2012 study in men with late-onset hypogonadism found 90% of subjects moved into the normal testosterone range after one month. These studies apply to their specific populations and extract types.

Is the SHBG mechanism real?

The SHBG story (Tongkat Ali inhibits SHBG to free up bound testosterone) is widely cited but less supported by the data than its prevalence suggests. At least one well-designed RCT found no significant SHBG change despite positive testosterone effects. The mechanism may be more complex than the SHBG narrative implies. We do not lead with it.

What dose does the research use?

Studied doses range from roughly 100 mg of standardized extract to 600 mg of a full-spectrum extract daily. The dose matters: the specific studies used specific extracts at specific doses in specific populations. Comparing across studies is complicated by these variables. Our product uses a 600 mg, 100:1 full-spectrum extract.

How long does it take to work?

The research outcomes in clinical trials emerged over 4–12 weeks of consistent daily use. For a full discussion of the timeline and what a fair trial looks like, see How long does Tongkat Ali take to work?

Is it safe?

Generally well-tolerated at sensible doses in healthy adults per the clinical literature, with specific contraindications that apply to certain health conditions and medications. For the full safety discussion including the EFSA question and the Health Canada cautions and contraindications, read Is Tongkat Ali safe? Side effects, honestly.

Referenced studies (selected)

  • 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 1:226-30.
  • 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.
  • Hamzah S, Yusof A. “The ergogenic effects of Eurycoma longifolia Jack: A pilot study.” British Journal of Sports Medicine. 2003; 37:464-470.
  • Chan KQ, Stewart C, Chester N, Hamzah SH, Yusof A. “The effect of Eurycoma longifolia on the regulation of reproductive hormones in young males.” Andrologia. 2021; 53(4).

This list is illustrative. The Examine.com Eurycoma longifolia summary provides a more comprehensive research overview: examine.com/supplements/tongkat-ali

What to read next

The research block above is ingredient science. It describes what studies examined about Eurycoma longifolia and is not a claim about what our product will do for you. The licensed claims (NPN 80133495) are stated separately and plainly. Talk to your healthcare provider for advice specific to your situation.