Benefits
Sexual Function: Studied Mostly in People With a Diagnosed Problem
Studied in 50 men with mild erectile dysfunction (2.4 g/day for 12 weeks). Both the maca group and the placebo group improved on the IIEF-5 erectile function score, so maca did not beat placebo on that measure. Maca did do better than placebo on a general satisfaction questionnaire, mainly its psychological and physical wellbeing sections. In 45 women whose sexual difficulties were caused by antidepressants, 3 g/day for 12 weeks improved two sexual function questionnaires more than placebo. This was studied in women taking medication, not in healthy users. A pilot study in 8 trained male cyclists also looked at self-rated sexual desire over 14 days. Eight people is far too few to conclude anything from.
Semen Parameters: One Small Uncontrolled Study
The only fertility study cited here is a 4-month open-label trial in 9 healthy adult men taking 1,500 or 3,000 mg/day. It reported higher semen volume, sperm count and sperm motility, with no change in testosterone, LH or FSH. There was no placebo group and no randomisation, and 9 men is tiny, so this is preliminary. No man with infertility was studied, and this does not show maca treats infertility.
Menopausal Symptoms: Limited Evidence
A 2011 systematic review found only four randomised trials of maca for menopausal symptoms. It reported favourable scores on menopause symptom scales, but the authors wrote that the evidence is limited and that the number of trials, the total sample size and the study quality were too limited to draw firm conclusions. Separately, a crossover trial in 14 postmenopausal women taking 3.5 g/day for 6 weeks lowered anxiety and depression scores, and its authors noted the effect was not related to the estrogen or androgen content of the maca.
Mood Scores in One Very Small Menopause Trial
One crossover trial in 14 postmenopausal women reported lower anxiety and depression scores after 3.5 g/day for 6 weeks. Fourteen people is far too small to establish a reliable effect. No study cited on this page tested maca in overweight or obese people, and maca is not a treatment for depression or anxiety.
Physical Performance: No Benefit Over Placebo
In the only exercise study cited here, 8 trained male cyclists took maca extract for 14 days. Their 40 km time trial times improved compared with their own starting times (p = 0.01), but they were not significantly better than placebo, which is the comparison that matters. This is a single pilot in 8 people and is not evidence that maca improves athletic performance.
Studied in Men With Symptoms of Late-Onset Hypogonadism
In 80 Korean men over 40 with symptoms of late-onset hypogonadism, 1,000 mg of maca three times a day, 3 g a day in total, for 12 weeks improved symptom, sexual function and urinary questionnaire scores more than placebo, without meaningfully raising testosterone. That dose sits within the range used by the other trials on this page. These were men with a diagnosed problem, not healthy men.
Mechanism of action
Antioxidant and Anti-Inflammatory Effects
Glucosinolates and flavonoids scavenge free radicals in laboratory tests. Whether that translates into any effect on sperm quality or menopausal symptoms in people is unknown; none of the human trials cited here measured oxidative stress. Glucosinolates (e.g., benzyl glucosinolate) break down into isothiocyanates, which affect inflammatory signalling in cell and animal experiments. That is laboratory work, not something measured in the human maca trials on this page.
Neuroendocrine Effects (Proposed, Not Demonstrated in People)
Maca contains fatty acid derivatives called macamides that are chemically similar to the body's own endocannabinoid compounds, and researchers have proposed they act on stress and mood pathways. That is a hypothesis from laboratory work. No human trial cited here measured HPA axis activity or cannabinoid receptors, so this remains an idea rather than a demonstrated mechanism.
Spermatogenesis Support
Maca’s effect on sperm has no established mechanism. Laboratory and animal work has suggested protection of testicular tissue from oxidative damage, but the one human semen study cited here was an uncontrolled 4-month trial in 9 men that measured no mechanism at all.
Maca Is Not an Estrogen
Maca does not contain plant estrogens and does not appear to change estrogen levels. In the postmenopausal trial cited here the authors specifically reported that the benefits were not related to the estrogen or androgen content of the maca. How maca might ease menopausal symptoms is simply not known.
Energy and Performance: Proposed, Not Supported by the Trials Here
Claims that maca improves mitochondrial efficiency, glucose metabolism, endurance or muscle recovery come from laboratory work, not from the human trials on this page. The one exercise trial cited here, in 8 cyclists, did not beat placebo, so there is no human result for this mechanism to explain.
Clinical trials
Randomized, double-blind, placebo-controlled trial in Italy in 50 Caucasian men with mild ED receiving maca dry extract (2,400 mg/day) vs placebo for 12 weeks. (Andrologia)
50 men with mild ED.
Both the maca and placebo groups improved on IIEF-5 erectile function scores, so maca was not better than placebo on that measure. Maca did produce significantly greater improvement than placebo on the SAT-P satisfaction profile, mainly its psychological and physical wellbeing sections. Critical context: PDE5 inhibitors (sildenafil, tadalafil) remain first-line for ED. Maca effects are smaller and more variable; may have role in mild ED or as adjunct.
12-week, double-blind, placebo-controlled trial at Massachusetts General Hospital in 45 women (mean age 42) with SSRI-induced sexual dysfunction. Outcomes: ASEX, MGH SFQ. (Evid Based Complement Alternat Med)
45 women with SSRI-induced sexual dysfunction.
Maca 3 g/day produced significantly greater improvement in libido and orgasmic function vs placebo. Effects modest but practically meaningful — SSRI-induced sexual dysfunction is a major adherence problem affecting ~50% of users.
Double-blind, randomized, pilot dose-finding study in 20 remitted depressed outpatients (17 women, mean age 36). (CNS Neurosci Ther)
20 remitted depressed outpatients on SSRIs.
Higher-dose maca (3 g/day) showed greater benefit on sexual function than lower doses. Established dose ranging for subsequent maca trials.
Evidence review of 4 randomized controlled trials assessing maca for menopausal symptoms in postmenopausal women. (Lee et al. 2011, Maturitas)
Pooled across 4 clinical trials.
The review found favourable scores on menopause symptom scales, but its authors concluded that the results provide only limited evidence, and that the number of trials, the total sample size and the average study quality were too limited to draw firm conclusions. Note: hormone therapy remains first-line for moderate-to-severe menopausal symptoms; maca is a modest non-hormonal option.
4-month open-label study in Peru in 9 healthy adult men taking 1,500 or 3,000 mg/day of maca. No placebo group and no randomisation. Outcomes: semen parameters and hormones. (Gonzales et al. 2001, Asian J Androl)
9 healthy adult men. No control group.
Semen volume, sperm count and sperm motility increased over 4 months, and testosterone, LH and FSH did not change. Because there was no placebo group, no randomisation and only 9 men, these changes could reflect chance or normal variation. Anyone worried about fertility should see a doctor; this study does not show maca treats infertility.
14-day, placebo-controlled crossover study at Northumbria University in 8 trained male cyclists receiving maca extract. (J Ethnopharmacol)
8 trained male cyclists. Crossover.
40 km time trial times improved against each cyclist's own baseline (p=0.01) but were NOT significantly better than placebo. Against placebo this was a null result. Very small sample (n=8) and a single pilot study; this is not evidence that maca improves athletic performance.
12-week randomized, double-blind, placebo-controlled trial in Korea in 80 men aged over 40 with symptoms of late-onset hypogonadism, taking 1,000 mg of maca three times a day (3 g a day in total). Outcomes: AMS symptom scores, sexual function (IIEF), urinary symptoms (IPSS) and testosterone. (Shin et al. 2023, World J Mens Health)
80 Korean men over 40 with symptoms of late-onset hypogonadism.
Maca significantly improved AMS symptom scores, IIEF sexual function scores and IPSS urinary symptom scores compared with placebo, without meaningfully raising testosterone. Note: maca is not a meaningful testosterone booster — multiple trials confirm minimal hormonal effects despite popular framing.
6-week, double-blind, placebo-controlled trial in 14 postmenopausal women receiving 3.5 g/day maca. Outcomes: GCS (Greene Climacteric Scale), HAM-A, HAM-D. (Menopause)
14 postmenopausal women. Very small.
Modest reductions in anxiety and depression scores vs placebo. Critical caveat: very small trial (n=14); cannot establish meaningful efficacy.