Maca Root: Evidence for Fertility, Hormones & Energy
What Is Maca?
Maca (Lepidium meyenii) is a cruciferous root vegetable native to the Junín plateau of the Peruvian Andes, grown at altitudes of 4,000–4,500 metres. It has been cultivated and consumed by indigenous Andean people for over 2,000 years — both as a food staple and as a medicinal plant for fertility, stamina, and endurance.
In supplement form, maca is sold as a powder (dried, ground root), extract capsules, or gelatinised maca (pre-cooked to improve digestibility). It sits within the broader category of adaptogens — plants that are purported to help the body maintain homeostasis under stress — though its mechanisms are distinct from classic adaptogens like ashwagandha or rhodiola.
The key bioactive compounds in maca include macamides (unique to maca), macaridine alkaloids, glucosinolates, and various polysaccharides. Macamides in particular are believed to influence endocannabinoid tone and fatty acid amide hydrolase (FAAH) activity, which may partially explain effects on mood and energy.
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The Most Important Misconception: Maca Is NOT a Phytoestrogen
This cannot be overstated. A significant portion of maca's marketing — particularly for women — implies it "balances hormones" by acting like a natural oestrogen. This is incorrect.
Maca does not contain phytoestrogens (plant compounds that bind to oestrogen receptors, like isoflavones in soy or lignans in flaxseed). Multiple in vitro studies have confirmed maca does not bind to oestrogen receptors. When researchers measure oestradiol levels after maca supplementation, they typically find no significant change in circulating oestrogen.
Why does this matter? Because women considering maca for breast cancer risk management, endometriosis, or oestrogen-sensitive conditions may have been told to avoid phytoestrogens. Maca appears safe in that context. But it also means any hormonal effects occur through a different, less well-understood pathway — possibly via the hypothalamus-pituitary axis or adrenal regulation rather than direct sex hormone manipulation.
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Evidence for Male Fertility
This is the strongest area of maca research with the most consistent evidence.
Sperm Quality RCTs
A 2001 RCT by Gonzales et al. in Asian Journal of Andrology found that 1,500mg or 3,000mg of maca daily for 4 months significantly increased sperm count and motility compared to placebo in healthy men aged 24–44. Serum testosterone, LH, FSH, and prolactin were all unchanged, suggesting the effect on sperm is not mediated through testosterone.
A 2009 systematic review by Shin et al. in BMC Complementary Medicine reviewed all available RCTs and concluded that "limited evidence shows maca use is associated with improved sperm production and motility." The authors noted the evidence base was small and studies were short-term, but the direction of effect was consistent.
The mechanism remains unclear but may involve improved testicular environment (antioxidant effects), better Sertoli cell function, or direct effects on spermatogenesis independent of androgens.
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Evidence for Female Health: Menopause and Libido
Menopausal Symptoms
A 2008 double-blind RCT by Meissner et al. published in Menopause found that 2g of gelatinised maca per day over 2 months significantly reduced hot flush frequency and night sweat severity in perimenopausal women compared to placebo. Notably, FSH and oestradiol did not change significantly, again pointing to a non-oestrogenic mechanism.
A smaller 2006 study found maca improved psychological wellbeing, energy, and depressive symptom scores in postmenopausal women over 6 weeks.
Libido in Postmenopausal Women
A 2008 randomised crossover trial by Brooks et al. published in Climacteric found that 3.5g/day of maca significantly improved sexual dysfunction and personal distress scores in postmenopausal women. Interestingly, the effect on libido appeared independent of depression and anxiety scores, suggesting it was not simply a mood-mediated effect.
SSRI-induced sexual dysfunction is an emerging use case — a 2015 pilot RCT (Dording et al.) found maca improved sexual function in antidepressant-treated women, though the study was small.
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Evidence for Energy and Fatigue
Maca's reputation as an "energy" supplement is partly folkloric (Andean farmers traditionally used it to sustain energy at altitude) and partly supported by small modern trials.
A 2009 RCT by Earnest et al. in the Journal of Strength and Conditioning Research found that competitive cyclists who supplemented with maca extract for 14 days had significantly improved 40km cycling time trial performance and self-reported sexual desire compared to baseline. Sample size was very small (n=8), limiting conclusions.
A 2016 trial found maca supplementation reduced self-rated fatigue in adults with chronic fatigue-type symptoms over 12 weeks. Effect sizes were modest.
The honest summary: maca may contribute to perceived energy and reduced fatigue, particularly in women during perimenopause or in men under physical training stress. It is unlikely to produce dramatic effects in healthy, well-nourished adults with no underlying fatigue or hormonal irregularity.
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Gelatinised vs Raw Maca
Raw maca powder contains goitrogens (glucosinolates) that can interfere with thyroid function with very high or prolonged consumption. For most people at typical doses (1.5–3g/day), this is not a concern, but those with hypothyroidism or who consume large amounts should be aware.
Gelatinised maca has been pre-cooked, which: - Destroys most goitrogens - Breaks down starch, improving digestibility - Concentrates the active compounds
Most clinical trials use gelatinised maca. For supplemental use, gelatinised or extract forms are preferable to large amounts of raw powder.
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Dosing
- General dose range in trials: 1.5g–3.5g per day - Standard supplement dose: 1.5–3g daily (1–2 capsules of most UK products) - Duration to see effects: Most fertility and menopausal symptom trials ran 8–16 weeks; do not expect to assess efficacy in under 6–8 weeks - Timing: Morning or with meals; maca is not sedating or stimulating enough to require specific timing for most people
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Limitations and Realistic Expectations
Most maca studies suffer from: - Small sample sizes (10–80 participants) - Short duration (4–16 weeks) - Industry funding in some cases - No standardisation of maca bioactive content between products
Maca is unlikely to produce dramatic hormonal effects in healthy people with normal hormone levels. Its strongest evidence is in populations with specific deficits: menopausal women, men with subfertility, and possibly people under prolonged physical stress.
It is a reasonable addition to a protocol for fertility support, menopausal symptom management, or chronic fatigue — but it should be seen as a contributing factor, not a standalone solution, and expectations should be calibrated to the modest effect sizes seen in trials.
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