Tongkat Ali: What the Clinical Trials Actually Show for Testosterone, Stress, and Sexual Health

Tongkat Ali has gone from Malaysian folk remedy to the most-discussed "natural testosterone" ingredient of the past decade. The research is more interesting than most herbal hype, and also more limited. Here's what it shows, who it seems to help, and why the extract's quality matters as much as the dose.

What Tongkat Ali is

Eurycoma longifolia is a slender shrub native to Malaysia, Indonesia, and Thailand. Its root has been used traditionally as a tonic for energy, fever, and male vitality. The compounds of interest are quassinoids, particularly eurycomanone, along with peptides sometimes marketed as "eurypeptides."

Proposed mechanisms

Laboratory and animal work suggests eurycomanone may act at several points: increasing release of testosterone from Leydig cells, inhibiting aromatase (the enzyme converting testosterone to estrogen), and reducing binding of testosterone to SHBG so more is free. It also appears to blunt cortisol. How much of this translates to humans at oral doses is the question the clinical trials try to answer.

The human evidence

Testosterone

Independent evidence A 2017 systematic review in the Chinese Journal of Natural Medicines examined 11 clinical studies and concluded Tongkat Ali showed "considerable effects" on male sexual health parameters, while flagging small samples and methodological variation. A 2022 meta-analysis found significant testosterone increases, particularly in men with low baseline levels or hypogonadism, and smaller effects in healthy young men.

A 2021 six-month randomized trial in men with age-related androgen deficiency found 200 mg/day of a standardized extract, combined with training, improved testosterone and erectile function scores versus placebo.

Stress and cortisol

Independent evidence A 2013 study in moderately stressed adults found 4 weeks of 200 mg/day reduced salivary cortisol by 16%, increased testosterone by 37%, and improved mood scores (tension, anger, confusion). It's a small study, and the extract was a branded one, but it's one of the more cited results in the field.

Sexual function

Independent evidence A 12-week trial in men with mild ED found 300 mg/day improved erectile function scores and sexual satisfaction versus placebo. Sperm quality improvements have also been reported in men with idiopathic infertility.

Who responds

Editorial The pattern across the studies is consistent: the biggest effects appear in men who are older, stressed, or have low-normal or low testosterone to begin with. In healthy young men with normal levels, the changes are small to nil. This is typical of adaptogens and worth remembering: if your testosterone is fine, Tongkat Ali isn't going to push it higher in any meaningful way. Our article on testosterone decline after 40 discusses who actually has low levels.

Dose and standardization

The studied doses are 200–400 mg/day of a standardized extract, most often a water extract at a 100:1 or 200:1 root-to-extract ratio, with eurycomanone content of roughly 1–2%. This matters enormously. Raw Tongkat Ali root powder is far weaker; 200 mg of powder is not remotely equivalent to 200 mg of a 100:1 extract. Products that don't specify an extract ratio or eurycomanone percentage are difficult to evaluate.

What this means for Tongkat Ali in Spartamax

Editorial On capacity alone, Tongkat Ali is one of the ingredients that could plausibly be present at a meaningful dose in a gummy; 200 mg of extract fits. But the vendor states neither the amount nor whether it's an extract or a powder, nor any standardization. It could be the formula's best-dosed ingredient or a token inclusion. The supplement facts page explains how to check when your bottle arrives.

Safety

• Generally well tolerated in trials up to 600 mg/day for several months.
• Some users report restlessness, irritability, or insomnia; taking it in the morning helps.
• Quality concerns are real: a 2006 Malaysian survey found some Tongkat Ali products contaminated with mercury. Buy from suppliers who publish testing.
• Not appropriate for men with hormone-sensitive cancers without oncology advice.
• Limited data in people with diabetes, though some effect on blood sugar has been reported.

Related: the ashwagandha article covers the other adaptogen in the Spartamax formula, and stress, cortisol, and male performance explains why both are in there.