Tongkat Ali

What it is

Tongkat ali is the root of Eurycoma longifolia, a slender tree native to Malaysia, Indonesia and Vietnam, where it has long traditional use as a tonic and aphrodisiac. It is also sold as Longjack, Pasak Bumi and Malaysian ginseng, none of which are botanically ginseng.

The active class is quassinoids, principally eurycomanone. Extraction method matters unusually much here: the trials with positive results almost all used water-based standardised extracts (typically 100:1), of which Physta and LJ100 are the two most studied. Ethanol extracts and raw root powder have very different compositions and are not interchangeable with the trial material.

What the trials show

Stress and hormones. A 2013 study in the Journal of the International Society of Sports Nutrition gave 200 mg daily of a standardised water extract to moderately stressed adults for four weeks and reported reduced tension, anger and confusion scores alongside an 11% reduction in cortisol and a 37% increase in salivary testosterone.

Hypogonadal men. A study in men with late-onset hypogonadism reported that 200 mg daily for one month moved the majority of participants from below to within the normal range for serum testosterone.

Sperm parameters. Trials in subfertile men report improvements in sperm concentration and motility over 3–9 months.

Body composition and strength. Results are mixed. Some trials in older men report improved lean mass and grip strength; others find no performance effect in trained athletes.

The pattern across the literature is that effects are clearest in men who are stressed, older or hypogonadal, and weakest in healthy young men with normal hormonal status — a recurring theme across this entire ingredient category.

The proposed mechanism

The most cited hypothesis is that eurycomanone reduces binding of testosterone to sex hormone-binding globulin, liberating more of the free, biologically active fraction without necessarily changing total production. There is also in-vitro evidence for effects on steroidogenic enzyme activity in Leydig cells, and the observed cortisol reduction offers an indirect route via the cortisol-testosterone ratio.

None of these are established to the standard of a well-characterised drug mechanism. They are plausible explanations consistent with the observed data.

Contamination — the practical safety issue

This is the point most worth knowing. Analyses of tongkat ali products sold in Malaysia and elsewhere have repeatedly found mercury contamination above permissible limits, along with lead and, in some cases, undeclared pharmaceutical adulterants. The plant accumulates heavy metals from soil, and the market includes a large volume of unregulated material.

The practical implication: buy only standardised, named extracts (Physta, LJ100 or equivalent) from suppliers who publish third-party heavy metal testing. This is not a category in which anonymous bulk powder is a reasonable purchase.

Beyond contamination, reported side effects are mild — insomnia and restlessness at higher doses, which is why morning dosing is standard. It should be avoided by men with hormone-sensitive conditions, and it has not been adequately studied in people with kidney or liver impairment. Cycling — for example five days on, two off — is common practice, though this is convention rather than evidence.