Tongkat Ali (Eurycoma longifolia)

Leitao et al. (Maturitas, 2021; PMID 33541567): 45 men with androgen deficiency of aging, four arms of placebo, 200 mg/day extract, concurrent training, or both for 6 months; the primary outcome was erectile function (IIEF-5) with the Aging Male Scale and total testosterone alongside, and the largest gains were in the extract-plus-training arm; the design does not isolate the extract's effect on testosterone. Chinnappan et al. (Food Nutr Res, 2021; PMID 34262417): 105 men aged 50 to 70 with testosterone below 300 ng/dL, 100 or 200 mg/day of a standardized water extract or placebo for 12 weeks; total testosterone rose, the primary endpoint; funded by the extract's maker, with two of its employees among the authors. Chan et al. (Andrologia, 2021; PMID 33559971): 32 healthy young men, 600 mg/day for 2 weeks; testosterone and free testosterone rose against placebo; university funded. Leisegang et al. (Medicina (Kaunas), 2022; PMID 36013514): meta-analysis of 5 randomized trials; pooled standardized mean difference 1.35 for total testosterone with I-squared about 87 percent, confirmed in the hypogonadal subgroup and not significant in healthy men. Morgado et al. (Int J Impot Res, 2024; PMID 37697053): systematic review of testosterone boosters rating this extract possibly effective in late-onset hypogonadism. Kotirum et al. (Complement Ther Med, 2015; PMID 26365449): meta-analysis of 2 randomized trials on erectile function, no overall difference. Grade C: small, inconsistent and largely maker-run evidence on a hormone level, positive in men with low testosterone and not in healthy men.