Tongkat Ali

What Tongkat Ali is

Tongkat Ali is botanically Eurycoma longifolia, a slow-growing tree from Southeast Asia, called Malaysian ginseng in Malaysia. The root is used. There, it has been boiled for centuries against fever and malaria and is traditionally regarded as a remedy for male vigor.

The main active compound is called eurycomanone. It belongs to the quassinoids, an extremely bitter class of molecules, and commercial extracts are usually standardized to it. The human studies consistently used a standardized water extract of the root, over periods of 2 to 12 weeks, in a single case over 6 months.

How it is supposed to work

The mechanism data come from the laboratory, not from humans. In Leydig cells from rat testes, eurycomanone increases testosterone production. The suspected explanation is an inhibition of aromatase, the enzyme that converts testosterone into estrogen. The pathway is plausible, but shown in cells and not quantified in humans.

The explanation found in almost every product text is a different one: Tongkat Ali supposedly releases bound testosterone from the transport protein SHBG, making it freely available. This narrative has been tested in humans, and it did not pass the test. In the human study in 32 young men, SHBG did not change. LH and FSH, the two control hormones from the pituitary gland, also remained unchanged. Testosterone rose significantly in the Tongkat group compared with placebo, though over only two weeks and in 16 men per group.

Why almost all the data come from a single extract

The body of research on Tongkat Ali is not broad, but deep in one spot. Of the 9 human studies reviewed by the meta-analysis, 7 used the same water extract, which belongs to a Malaysian company. This manufacturer funded several of the important papers, and in two of them authors are employed there.

That does not make the results wrong. But it does mean that it remains open whether any Tongkat powder on the market does the same as this one standardized extract. The available product analyses suggest that it is often not even the same plant.

What the studies show

Meta-analysis of 5 randomized studies, 2022

Leisegang and colleagues reviewed 9 human studies and pooled 5 randomized trials among them with a total of 232 men. The overall result is a significant rise in testosterone. The same paper states three limitations: 7 of the 9 studies used the same company extract, heterogeneity between the studies was 87 percent, and in the subgroup of healthy men the effect was no longer significant.

Double-blind study in 105 men with low testosterone

The methodologically cleanest study on exactly the group in question: 105 men between 50 and 70 years of age with a baseline value below 300 nanograms per deciliter, 12 weeks, double-blind against placebo. The testosterone value rose from around 200 to 225; under placebo it fell slightly. The difference is statistically significant. It amounts, however, to 25 points, and the normal range only begins at around 300. Both first authors are employees of the manufacturer that paid for the study.

The largest study in healthy men, 109 participants

In 109 healthy men over 12 weeks, there was no difference from placebo. This is the largest single study in this group. It was not included in the meta-analysis; the meta-analysis's subgroup of healthy men comprises only 3 small studies with 88 participants and is likewise not significant.

Tambi 2012: the study behind the advertising figure

76 men with late-onset hypogonadism took a standardized extract for one month. The testosterone value rose on average from 163 to 240 nanograms per deciliter, that is, by almost half. This study had no placebo group. It is a before-and-after comparison without a control, and exactly this figure still appears in product texts today.

Stress study in 63 adults

63 stressed adults, men and women mixed, took Tongkat Ali for 4 weeks. A 16 percent drop in cortisol and a 37 percent rise in testosterone were measured. The values come from saliva, not from blood. The study was funded by the manufacturer, and a co-author is employed there. The 37 percent is the figure most often used to advertise the category.

Where the data stop

For healthy men with normal testosterone levels, there is no robust evidence of efficacy. The meta-analysis's subgroup analysis is not significant here, and the largest single study in this group shows no difference from placebo. Anyone reaching for Tongkat Ali without a deficiency has, so far, no data basis for the hoped-for hormonal effect.

It also remains open what a rise of a few dozen points means in everyday life. In the cleanest study, the value ended at 225 nanograms per deciliter, while the normal range only begins at around 300. The participants thus remained below the threshold that mattered to them. Endpoints such as muscle mass, erectile function, mood or fertility have at most been recorded as questionnaire scores over a few weeks. For periods beyond 12 weeks, there is practically nothing; a single study extends over 6 months.

Status, approval and legal

In the European Union, Tongkat root extract is considered a novel food and therefore requires authorization. The manufacturer has applied for it. In 2021, the European food safety authority responded that safety had not been established. The reason was evidence of DNA damage in the stomach and duodenum, which had appeared in a chromosome test on cells and in an animal study. Without this authorization, sale as a food supplement is not permitted in the EU, and Tongkat products regularly appear in the European rapid alert system as unauthorized novel food. That the products are nonetheless widely available does not change the legal situation. A low testosterone level is, moreover, a medical diagnosis and not a self-assessment.

Safety

The safety data cover weeks, not years. No serious events have been reported from the controlled studies. Alongside this, there are four concrete signals. First, the liver: in 2024 a case was published, a 47-year-old with jaundice one week after starting intake and recovery after stopping. The US liver database lists Tongkat Ali as a possible, rare cause and at the same time points out that undisclosed steroid use can never be completely ruled out in such cases. Second, product quality: in Malaysia in 2004, a total of 100 Tongkat products were tested for mercury, and 36 were above the limit. A DNA test from 2018 found the correct plant unambiguously in only 37 percent of the products. Third, an interaction: the absorption of the beta blocker propranolol drops by almost a third. Fourth, the genotoxicity signal on which the European authority bases its rejection. In hormone-dependent conditions and with ongoing medication, the question belongs in the hands of a physician.

Sources

• Leisegang et al., Medicina 2022 — meta-analysis of 5 randomized studies
• Chinnappan et al., Food & Nutrition Research 2021 — double-blind study in 105 men with testosterone below 300 ng/dl, 12 weeks
• Tambi et al., Andrologia 2012 — uncontrolled study in 76 men
• Talbott et al., Journal of the International Society of Sports Nutrition 2013 — manufacturer-funded stress study in 63 adults, saliva measurement
• Chan et al., Andrologia 2021 — human study in 32 young men, SHBG, LH and FSH unchanged
• EFSA opinion on the novel food application, EFSA Journal 2021
• Kaliounji et al., Cureus 2024 — case report of liver injury
• US liver database LiverTox, Tongkat Ali monograph
• Ang HH et al., International Journal of Toxicology 2004 — mercury testing of 100 Malaysian Tongkat Ali products
• Abubakar BM et al., Pharmaceutical Biology 2018 — DNA testing of Tongkat Ali products