Maca

What it is

Maca (Lepidium meyenii) is a root vegetable from the Andes in the mustard family, used for centuries in Peru as a food and traditional remedy for fertility and energy [1]. It is sold as powder, capsules and extracts. Most human trials used about 3 g a day of maca powder or an equivalent preparation [2].

How it might work

How maca works is not settled [3]. Trials that measured hormones found no change in testosterone, estradiol or other sex hormones, and lab tests found no oestrogen- or androgen-like activity in maca extracts, so any effect is probably not hormonal [4][5].

What the research says

Sexual desire and function. A 2010 systematic review (a study that pulls together all the trials on a question) found only four placebo-controlled trials. Two suggested a benefit, one in healthy men's sexual desire and one in menopausal women's sexual dysfunction, one in men with erectile dysfunction showed a benefit, and one in healthy cyclists found none [6]. In a 12-week trial of healthy men aged 21 to 56, sexual desire improved from week 8 on 1.5 g or 3 g a day, and the effect was not explained by changes in mood or testosterone [7]. In 20 people with sexual problems caused by SSRI antidepressants, those who took 3 g a day had better sexual-function scores after the study period (ASEX score from 22.8 to 16.9), while those on 1.5 g a day did not [8]. In 50 men with mild erectile dysfunction, scores on a standard questionnaire (IIEF-5) rose by 1.6 points on 2,400 mg of maca extract and by 0.5 points on placebo over 12 weeks [9].

Menopausal symptoms. A 2011 review of four trials found that all of them reported favourable effects on standard menopause symptom scores, though it called the evidence limited [1]. In a crossover trial of 14 postmenopausal women, 3.5 g a day for six weeks lowered psychological symptoms, including anxiety and depression, and sexual-dysfunction scores compared with placebo [5]. In 29 postmenopausal women, 3.3 g a day for six weeks lowered depression scores and diastolic blood pressure compared with placebo [10].

Hormones. In a 12-week trial of healthy men, 1.5 g or 3 g a day of maca did not change testosterone, estradiol, LH, FSH or prolactin compared with placebo [4]. Postmenopausal women also showed no change in estradiol, FSH or SHBG on maca [5][10].

Sperm quality. Results are mixed. In 69 men with mild semen problems, 2 g a day for 12 weeks raised sperm concentration compared with placebo (15.04 vs 10.16, p = 0.011) but did not change semen volume, sperm movement or shape [11]. In 50 infertile patients, sperm concentration rose 40% on maca and 76% on placebo over 16 weeks, a non-significant difference, and free testosterone fell on maca [12].

Exercise performance. A 2024 meta-analysis reported large effects of maca on physical performance, but its main measures were animal tests such as forced swimming and rota-rod [13]. In ten well-trained basketball players, two weeks of 2 g a day gave no benefit for jumping, sprinting, shooting accuracy or fatigue [14].

Doses used in studies

Most trials used about 3 g a day of maca powder or an equivalent [2]. Examples: 1.5 g or 3 g a day for 12 weeks in healthy men [7]; 1.5 g or 3 g a day in the SSRI study [8]; 2,400 mg of dry extract for 12 weeks in men with mild erectile dysfunction [9]; 2 g a day for 12 weeks in men with semen problems [11]; and 3.3 to 3.5 g a day for six weeks in postmenopausal women [5][10]. These are the amounts tested, not recommendations.

Safety and interactions

Side effects. Maca was described as well tolerated in the SSRI study of 20 people [8]. In a 90-day trial of a silymarin and maca combination (0.6 g a day of maca) in people with metabolic syndrome, volunteers on maca showed a moderate rise in the liver enzyme AST and in diastolic blood pressure, and the authors advised caution with high doses of maca powder [15]. In contrast, a six-week trial in postmenopausal women found lower diastolic blood pressure on maca [10]. Animal and lab studies suggest low toxicity [3].

Upper limits. No safe upper limit has been set. Trials ran for up to 16 weeks at up to 3.5 g a day [12][5]. Quality varies between products, and a toxicology review stressed the need to standardise them [3].

Medicines. The only medicine-related data come from the SSRI study, where maca was taken alongside antidepressants without major problems reported [8]. We found no formal drug-interaction studies.

Pregnancy and breastfeeding. We found no human safety data for pregnancy or breastfeeding.

Kidney, liver and bleeding disorders. We found no studies in people with kidney or liver disease or bleeding disorders. The AST rise noted above is relevant to people with liver conditions [15].

Hormone-sensitive conditions. In small trials maca did not change sex-hormone levels [4][5], but there are no long-term data in people with hormone-sensitive cancers.

Caveats and open questions

Reviewers have repeatedly called the trial numbers and quality too limited to draw firm conclusions [6][1]. Most trials had fewer than 70 people, and several were pilots. Some of the strongest effects are in questionnaire scores that placebo also improved [9].