1.5–3 g/day of powdered root.
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Maca is a cruciferous plant (of the family of cabbage, radish, and broccoli) that grows exclusively in the Peruvian Andes at more than 4,000 meters of altitude, where the extreme conditions of cold, wind, and UV radiation produce a tuber with a unique phytochemical composition that pre-Incan civilizations used as a staple food and as a tonic for fertility and energy; modern scientific research has confirmed a modest but replicable clinical profile in libido, sexual function, and subjective well-being.
Unlike many "adaptogen" supplements promoted as general tonics, maca has the peculiarity of not acting on classic hormone receptors (it does not directly increase testosterone, estrogen, or growth hormone) but instead appears to modulate the activity of the hypothalamic-pituitary-gonadal axis without altering baseline hormone levels, a property that makes it an interesting option for people seeking benefits for libido or energy without the concerns of direct hormonal modulation.
The strongest evidence for maca is its effect on libido in adult men and women: several randomized trials have shown significant improvements in subjective sexual desire with doses of 1,500-3,000 milligrams daily of dried maca for 8-12 weeks, with no changes in plasma testosterone or estradiol, which sets its effect apart from that of other pseudo-androgens on the market.
In SSRI-induced sexual dysfunction (one of the most frequent and persistent adverse effects of serotonergic antidepressants), several studies have shown significant improvements with high doses (3,000 mg/day) over several weeks, a clinically relevant indication because few options exist for managing this problem without stopping the antidepressant or switching to another with a different profile.
For general well-being and quality of life, several trials have shown subjective improvements with doses of 1,500-3,000 mg/day for 8-12 weeks, especially in people with low baseline well-being due to stress, fatigue, or mild depressive symptoms; the effect is modest but replicable and is noticed gradually, not acutely like stimulants.
In postmenopausal women, several trials have shown significant reductions on climacteric symptom scales (Greene, Kupperman) with doses of 2,000 mg/day for 12 weeks, especially in hot flashes, night sweats, and decreased libido; the effect is comparable to that of some phytoestrogens without acting directly on estrogen receptors, which makes it a reasonable alternative for women with a contraindication to pharmaceutical estrogens.
There are three main commercial varieties with slightly different profiles: yellow maca (the most common and cheapest, with a general profile), red maca (with specific data in prostatic hyperplasia and antioxidant activity), and black maca (the most studied for libido and physical performance, especially in men); some premium products market "three-color maca," combining the three varieties to cover the spectrum of effects.
The doses studied range from 1,500 to 3,000 milligrams daily of dried powder or the equivalent as a standardized extract (gelatinized for better digestibility), divided into one or two doses with or without food; gelatinized products are the most digestible for people with gastrointestinal sensitivity to raw maca; clinical effects appear between 6 and 12 weeks, so it is not a fast-acting compound.
Generally well tolerated; adverse effects are rare and mild (digestive discomfort, occasionally insomnia if taken late, mildly activating); people with thyroid disease should use caution because maca is a cruciferous plant and contains mild goitrogens that, at high doses over a prolonged period, could interfere with thyroid function; those taking hormonal drugs (contraceptives, hormone replacement therapy) can use it because maca does not appear to interfere with hormone receptors, but they should consult before starting; in pregnancy and breastfeeding, data are limited, although Andean populations traditionally consume it as a food during these periods.
Information, not medical advice. Scientific evidence reflects the quality of the studies.