Tongkat ali has mainly been studied for its use as an aphrodisiac. However, the mechanisms by which tongkat ali may enhance aphrodisia are not well understood, and most of the research has been conducted in animals. This effect seems to be based in lore and tradition rather than hard evidence.
Supplementation may increase total testosterone in healthy and hypogonadal men, improve erectile function and alleviate symptoms of erectile dysfunction, increase fertility, and enhance sexual function and well-being.[1][2][3] One study found evidence of an anxiolytic (anxiety and stress-reducing) effect of tongkat ali.[4] It should be noted that evidence for these outcomes is somewhat limited given the lack of published randomized controlled trials in humans.