Benefits
Total testosterone in middle-aged men, combined with exercise
In a six-month trial, 45 men averaging 47 years with age-related androgen deficiency took placebo or 200 mg of whole tongkat ali root extract a day, each with or without supervised training three times a week. Total testosterone rose in the group combining extract and training. In a separate four-week trial in stressed adults, salivary testosterone rose 37 percent on the extract.
Sexual function in men, combined with exercise training
In the same six-month trial, erectile function scores improved with both the extract and the exercise training, and the largest gains came in the group that combined them. Libido was not reported as a separate outcome, the groups held only about 11 men each, and the extract was whole root rather than purified eurycomanone.
Lower cortisol and tension in stressed adults (whole tongkat ali extract)
Whole tongkat ali root extract was tested, not purified eurycomanone. In 63 moderately stressed adults, 200 mg a day of a standardized hot-water root extract for 4 weeks gave 16 percent lower salivary cortisol exposure and 11 percent lower tension scores than placebo; depression, vigor and fatigue did not differ. The trial was funded by the extract's maker.
Mechanism of action
Aromatase inhibition (lab evidence)
In rat testis cells, eurycomanone lowered estrogen production in a way consistent with blocking aromatase, the enzyme that turns testosterone into estrogen, and computer docking showed it binding aromatase like the drug formestane. No study cited here measured estrogen or aromatase activity in people.
Testosterone production in Leydig cells (lab evidence)
In isolated rat Leydig cells, the testosterone-making cells of the testes, eurycomanone raised testosterone output in a dose-dependent way, and at high concentrations may also act by blocking phosphodiesterase. This has not been measured in people.
Cortisol and the stress response
One 4-week trial of whole root extract found lower salivary cortisol than placebo. How the extract does this, and whether eurycomanone is responsible, has not been shown.
Clinical trials
Six-month randomized, double-blind, placebo-controlled four-arm trial of 200 mg a day of Eurycoma longifolia extract or placebo, each with or without concurrent training three times a week (Leitão et al. 2021, Maturitas).
45 men, mean age 47, with androgen deficiency of the aging male; about 11 per group.
Erectile function (IIEF-5) improved with both interventions, with the clearest results in the group combining extract and training, which also had higher total testosterone. The authors listed limits in separating the effect of each intervention. The extract was whole root, not purified eurycomanone.
Four-week randomized, placebo-controlled trial of 200 mg a day of a standardized hot-water root extract (Physta). Funded by its maker, Biotropics Malaysia, which employed one author (Talbott et al. 2013, J Int Soc Sports Nutr).
63 adults (32 men, 31 women) screened for moderate stress.
With the extract, salivary cortisol exposure fell 16 percent and salivary testosterone rose 37 percent, and Tension, Anger and Confusion scores improved by 11 to 15 percent. Depression, Vigor and Fatigue scores did not differ from placebo. Two people on the extract and one on placebo felt unusually tired in the first two weeks.