Research dossier
Clinical research on Maca Root
9 trials reviewed across 6 indications.
Strongest evidence
Sexual desire & libido
Mechanism
Unknown and explicitly non-hormonal — the desire effect in Gonzales' trials occurred with no change in testosterone or mood scores. Proposed (unconfirmed) mechanisms involve maca's macamides/macaenes acting on central or vascular pathways rather than the endocrine system.
Maca's best-supported claim, and it is still weak. A 12-week RCT (Gonzales 2002) improved self-reported sexual desire in men, independent of testosterone, and two other small trials echoed a desire signal. But the 2010 systematic review judged the evidence 'limited' — small samples, subjective outcomes, low quality. A real-but-soft signal, not proven efficacy.
A modest, hormone-independent libido signal in healthy men. Outcomes are subjective self-report and the systematic review rates the evidence limited. Promising, not established.
Trials cited
Maca and sexual desire in healthy men
positive · RCT
Gonzales et al., 2002, Andrologian=57The flagship maca trial. After 8 and 12 weeks, men taking either dose of maca reported improved sexual desire versus placebo. Crucially, the authors specifically checked and found the effect was NOT explained by changes in serum testosterone, nor by changes in mood (Hamilton anxiety/depression scores). The libido signal exists; the testosterone mechanism does not.
Single-center, subjective self-report of desire (prone to expectancy effects), and no dose-response (1500 mg worked as well as 3000 mg). A real but soft signal — the basis for most maca-libido marketing.
Maca for sexual function (systematic review of 4 RCTs)
mixed · Systematic review
Shin et al., 2010, BMC Complementary and Alternative Medicinen=131Pooled the four maca RCTs that existed in 2010. Two trials suggested improved sexual desire in healthy men and one improved sexual function in mild ED, but the review's own verdict was that the evidence is 'limited' — too few trials, small samples, and low methodological quality to draw firm conclusions. The honest read on maca-and-libido in one citation.
The review explicitly warns the trials are too small and low-quality for firm conclusions. It is the best summary of the libido evidence — and that summary is 'weak, not proven.'
Maca extract for mild erectile dysfunction
mixed · RCT
Zenico et al., 2009, Andrologian=50The only ED trial, and an honest cautionary tale. Both the maca group AND the placebo group significantly improved their IIEF-5 erectile scores. Maca outperformed placebo only on some subjective well-being subscales, not on the core erectile-function measure. A weak, preliminary signal heavily contaminated by a strong placebo response.
Small (n=50) and the placebo arm also improved on the primary endpoint — so the erectile benefit attributable to maca is marginal. This is also the only trial using a concentrated 'extract' rather than dried root powder.
Maca, cycling performance, and sexual desire in athletes
mixed · Pilot
Stone et al., 2009, Journal of Ethnopharmacologyn=8A tiny crossover pilot (n=8). Maca improved 40 km time-trial performance versus the participants' OWN baseline — but NOT versus placebo, which is the comparison that actually matters. The sexual-desire score did beat placebo. So: no credible athletic-performance benefit, and a faint repeat of the libido signal.
Only 8 athletes and 14 days. The performance 'benefit' vanished against placebo. Frequently miscited as evidence maca boosts endurance — it does not, on this data.
Menopausal symptoms
Mechanism
Non-estrogenic — both menopause trials specifically found maca's symptom effects were unrelated to estrogenic or androgenic activity. Proposed central mood-modulating action remains unconfirmed.
Small crossover trials (Brooks 2008 n=14, Stojanovska 2015 n=29) showed reduced anxiety, depression, and a modest blood-pressure drop in postmenopausal women — and notably NOT via hormones. The 2011 systematic review found all four trials 'favorable' but rated the evidence limited and flagged shared authorship and commercial ties. A genuine but small mood signal.
Small trials with subjective endpoints, and the supporting review flags researcher/funding overlap. Maca is not hormone-replacement therapy and the effect is non-hormonal.
Maca for psychological symptoms in postmenopausal women
positive · RCT
Brooks et al., 2008, Menopausen=14A small crossover trial: maca reduced anxiety, depression, and sexual-dysfunction scores on the Greene Climacteric Scale versus placebo. The authors specifically tested and found the benefit was NOT related to estrogenic or androgenic activity — reinforcing that maca's effects are hormone-independent, the same theme as the male trials.
Very small (n=14), subjective questionnaire outcomes. The non-hormonal mechanism finding is the most reliable takeaway; the symptom benefit is preliminary.
Maca, blood pressure, and depression in postmenopausal women
positive · RCT
Stojanovska et al., 2015, Climactericn=29A crossover pilot in 29 postmenopausal women: maca reduced diastolic blood pressure and depression scores versus placebo. Consistent with Brooks 2008's mood signal, and again the effects appeared independent of estrogenic activity. Reinforces a small, real menopausal-mood signal — without a hormonal explanation.
Pilot-scale (n=29), crossover, and the BP effect was modest. Worth noting alongside Brooks but not confirmatory on its own.
Maca for menopausal symptoms (systematic review of 4 RCTs)
mixed · Systematic review
Lee et al., 2011, Maturitasn=192Pooled four RCTs of maca for menopausal symptoms. All four reported favorable effects on symptom scales — but the review's conclusion was that the evidence is 'limited' due to small samples and methodological weaknesses, and that the favorable trials share authors/funding ties. Promising direction, not established efficacy.
The review flags that the underlying trials are few, small, and several share the same research group and commercial connections (a defined branded maca product). Treat the consistent 'favorable' direction with appropriate skepticism.
Testosterone & sex-hormone support
Mechanism
Marketed as a natural endocrine 'adaptogen' that raises testosterone. There is no validated mechanism: maca is not phytoestrogenic and does not contain steroidal hormone precursors that survive to alter human serum hormones.
This is the claim maca is sold on, and controlled trials contradict it. Gonzales 2003 found NO change in testosterone, LH, FSH, prolactin, or estradiol over 12 weeks; Melnikovova 2015 found hormones unchanged in younger men; Brooks 2008 confirmed maca's effects in women were unrelated to estrogenic/androgenic activity. Maca does not move sex hormones.
No human evidence that maca raises testosterone or any sex hormone in healthy adults. 'Natural test booster' marketing is false — any benefit maca has is hormone-independent.
Maca and serum reproductive hormones in men
Null · RCT
Gonzales et al., 2003, Journal of Endocrinologyn=56The trial that kills the testosterone-booster claim. Across 12 weeks, maca had NO effect on any measured hormone versus placebo — testosterone, LH, FSH, prolactin, estradiol, and 17-OH-progesterone were all unchanged. Whatever maca does for libido, it does not work by altering sex hormones.
Same cohort/program as the 2002 desire trial. Directly refutes 'maca boosts testosterone' in exactly the demographic the supplement is marketed to.
Maca for psychological symptoms in postmenopausal women
positive · RCT
Brooks et al., 2008, Menopausen=14A small crossover trial: maca reduced anxiety, depression, and sexual-dysfunction scores on the Greene Climacteric Scale versus placebo. The authors specifically tested and found the benefit was NOT related to estrogenic or androgenic activity — reinforcing that maca's effects are hormone-independent, the same theme as the male trials.
Very small (n=14), subjective questionnaire outcomes. The non-hormonal mechanism finding is the most reliable takeaway; the symptom benefit is preliminary.
Maca, semen parameters, and hormones in healthy men
mixed · Pilot
Melnikovova et al., 2015, Evidence-Based Complementary and Alternative Medicinen=20Sperm concentration and motility showed 'rising trends' versus placebo over 12 weeks, but the abstract does not report these reaching statistical significance — a weak, preliminary fertility hint at best. Serum hormones again did NOT change significantly, consistent with every other controlled maca hormone measurement.
Small pilot (n=20), and the sperm improvements were described only as 'rising trends,' not significant effects. The hormone null result is the more solid finding.
Erectile function
Mechanism
Hypothesized vascular/central effect on arousal; no confirmed mechanism for erectile improvement.
A single small RCT (n=50) in mild ED. Both maca and placebo improved IIEF-5 erectile scores significantly — meaning the maca-attributable benefit on the core erectile measure was negligible. Maca beat placebo only on some subjective well-being subscales. Preliminary at best, and confounded by a large placebo response.
One small trial where placebo improved as much as maca on the primary endpoint. Not a basis to recommend maca for erectile dysfunction.
Maca extract for mild erectile dysfunction
mixed · RCT
Zenico et al., 2009, Andrologian=50The only ED trial, and an honest cautionary tale. Both the maca group AND the placebo group significantly improved their IIEF-5 erectile scores. Maca outperformed placebo only on some subjective well-being subscales, not on the core erectile-function measure. A weak, preliminary signal heavily contaminated by a strong placebo response.
Small (n=50) and the placebo arm also improved on the primary endpoint — so the erectile benefit attributable to maca is marginal. This is also the only trial using a concentrated 'extract' rather than dried root powder.
Energy, mood & athletic performance
Mechanism
Popularly framed as an 'energizing adaptogen.' No validated mechanism and no metabolic or endocrine pathway demonstrated in humans.
Among maca's most popular consumer claims and among its weakest. The one athletic trial (Stone 2009, n=8) improved cycling time only versus participants' own baseline, NOT versus placebo — the comparison that matters. There is no clean RCT showing maca improves energy or reduces fatigue in healthy adults.
No controlled evidence maca improves energy or athletic performance. The 'natural energizer' positioning is unsupported.
Maca, cycling performance, and sexual desire in athletes
mixed · Pilot
Stone et al., 2009, Journal of Ethnopharmacologyn=8A tiny crossover pilot (n=8). Maca improved 40 km time-trial performance versus the participants' OWN baseline — but NOT versus placebo, which is the comparison that actually matters. The sexual-desire score did beat placebo. So: no credible athletic-performance benefit, and a faint repeat of the libido signal.
Only 8 athletes and 14 days. The performance 'benefit' vanished against placebo. Frequently miscited as evidence maca boosts endurance — it does not, on this data.
Male fertility
Mechanism
Animal studies show spermatogenesis effects (notably in rodents/livestock); human translation is unproven.
Despite maca's folk reputation as a fertility root, the only human RCT (Melnikovova 2015, n=20) found sperm concentration and motility showed only 'rising trends' versus placebo — not statistically significant improvements. Hormones were unchanged. The fertility claim rests largely on animal data that has not translated to confirmed human benefit.
Human fertility evidence is one small pilot with non-significant 'trends.' Animal sperm data does not establish a human benefit.
Maca, semen parameters, and hormones in healthy men
mixed · Pilot
Melnikovova et al., 2015, Evidence-Based Complementary and Alternative Medicinen=20Sperm concentration and motility showed 'rising trends' versus placebo over 12 weeks, but the abstract does not report these reaching statistical significance — a weak, preliminary fertility hint at best. Serum hormones again did NOT change significantly, consistent with every other controlled maca hormone measurement.
Small pilot (n=20), and the sperm improvements were described only as 'rising trends,' not significant effects. The hormone null result is the more solid finding.
4 forms of Maca Root compared
Gelatinized maca root powder
Improved digestibility — heat/pressure treatment gelatinizes starch and reduces fiber, easing GI tolerance
Best forSexual desire (the form used in the Gonzales libido and hormone trials)This is the form behind maca's best evidence: Gonzales 2002/2003 used gelatinized maca at 1500–3000 mg/day. Gelatinization aids digestion but does not concentrate actives — it is still whole-root material, not an extract.
Raw dried maca root powder
Whole-food matrix; raw powder retains glucosinolates and goitrogens
Best forGeneral use; the form/dose range most trials are built on (1.5–3.5 g/day)The clinically studied material. Raw (non-gelatinized) powder contains goitrogenic glucosinolates that traditional preparation reduces by boiling — relevant for anyone with thyroid concerns.
Color-differentiated maca (black / red / yellow)
Same whole-root material; color is a phenotype, not a standardized active fraction
Best forMarketed as color-specific (black→cognition/sperm, red→prostate), but this is preclinical, not human-validatedPreclinical rodent work hints black maca may favor cognition/sperm and red maca may affect prostate — but NO human trial has validated buying maca by color. The human RCTs did not differentiate color. Treat color-specific marketing as unproven.
Concentrated maca extract (4:1, 10:1)
Higher actives per gram in theory, but extract ratios are not clinically validated for maca
Best forOnly one RCT (Zenico 2009) used an extract — and its core erectile endpoint matched placeboCommercial '4:1' or '10:1' extracts are NOT the form behind maca's positive trials, which used 1.5–3.5 g of whole dried/gelatinized root. There is no validated extract-to-powder equivalence, so an extract dose cannot be reliably mapped to the trial doses.
Side effects and drug interactions
Side effects
GI upset and bloating
Common
Mild gas, bloating, or cramping, generally dose-related. Maca is consumed as a food in the Andes and is well tolerated by most people.
Insomnia or jitteriness
Uncommon
Some users report feeling stimulated or having disrupted sleep, particularly at higher doses or when taken late in the day.
Goitrogen exposure (raw maca)
Uncommon
Raw, non-gelatinized maca contains glucosinolates with goitrogenic potential. Traditional preparation boils the root to reduce them. Relevant mainly for people with thyroid conditions or low iodine intake consuming large amounts of raw powder.
Worse with:dried root powder
Gentler:gelatinized maca
Drug interactions
Other
hormone-sensitive conditions (estrogen-sensitive cancers, endometriosis, uterine fibroids)Although controlled trials found maca does NOT alter sex hormones, caution is precautionary given its traditional reputation and limited long-term human data.
Discuss with a clinician before use if you have a hormone-sensitive condition. The hormonal-activity concern is precautionary, not demonstrated.
Additive effect
antihypertensivesOne small menopause trial (Stojanovska 2015) found a modest blood-pressure reduction; an additive effect with BP medication is theoretically possible.
Monitor blood pressure if combining; the human evidence is a single small pilot, so this is precautionary.
Other critical caveats
- Maca does NOT raise testosterone or any sex hormone. A controlled trial (Gonzales 2003) measured testosterone, LH, FSH, prolactin, and estradiol over 12 weeks and found no change versus placebo. The 'natural testosterone booster' positioning is contradicted by the actual data — any benefit maca has is hormone-independent.
- The best-supported claim is improved sexual desire in men, but even that evidence is rated 'limited' by its own systematic review (Shin 2010): few, small, low-quality, subjective-outcome trials. Treat it as a soft signal, not proven efficacy.
- All positive maca trials used 1.5–3.5 g/day of DRIED or GELATINIZED ROOT POWDER, not concentrated extracts. Commercial '4:1' and '10:1' extracts and color-differentiated (black/red/yellow) products are not clinically validated, and there is no reliable way to map an extract dose to the studied root-powder doses.
- Energy, athletic-performance, and male-fertility claims are not supported by controlled human evidence. The one athletics trial showed no benefit versus placebo; the one fertility trial showed only non-significant 'trends.'
Frequently asked
Does maca boost testosterone?
No. A controlled trial (Gonzales 2003) measured testosterone, LH, FSH, prolactin, and estradiol in men over 12 weeks and found no change versus placebo. A second trial in younger men (Melnikovova 2015) also found hormones unchanged. Maca is sold as a 'natural testosterone booster,' but controlled human trials show it does not raise testosterone or any sex hormone.Does maca actually help libido?
Possibly, modestly. A 12-week RCT (Gonzales 2002) found improved self-reported sexual desire in men — and notably, the effect was independent of testosterone. But the 2010 systematic review that pooled the maca sexual-function trials concluded the evidence is 'limited': few trials, small samples, subjective outcomes, low methodological quality. It's a real-but-weak signal, not proven.What dose of maca should I take, and which form?
The trials used 1.5–3.5 g/day of dried or gelatinized maca root powder. Gelatinized powder is gentler on digestion and is the form behind maca's best libido evidence. Be skeptical of concentrated '4:1' or '10:1' extracts and color-specific (black/red/yellow) products — those are not the forms that were studied, and there's no validated way to convert an extract dose to the studied root-powder dose.Will maca give me more energy or improve my workouts?
There's no good evidence for either. The only athletic trial (Stone 2009, 8 cyclists) found maca improved cycling time versus the riders' own baseline but NOT versus placebo — the comparison that matters. No clean RCT shows maca improves energy or reduces fatigue in healthy adults. The 'natural energizer' claim is marketing, not data.Is maca safe?
For most people, yes — maca is eaten as a food in the Andes and is generally well tolerated, with mild GI upset the most common complaint. Two caveats: raw (non-gelatinized) maca contains goitrogens, so people with thyroid conditions should prefer gelatinized maca or boiled preparations; and long-term human safety data is limited. Caution in hormone-sensitive conditions is precautionary, since trials show maca doesn't actually move hormones.
References
- 01Gonzales et al., 2002 — Maca on sexual desire, no relationship to testosterone (Andrologia)
- 02Gonzales et al., 2003 — Maca does not affect serum reproductive hormones in men (J Endocrinol)
- 03Shin et al., 2010 — Maca for sexual function, systematic review (BMC Complement Altern Med)
- 04Lee et al., 2011 — Maca for menopausal symptoms, systematic review (Maturitas)
- 05Memorial Sloan Kettering — Maca (About Herbs)
- 06Examine.com — Maca
Last reviewed2026-05-24