Maca

Maca is the root of Lepidium meyenii, a member of the brassica family related to radish and turnip, grown at high altitude in the Peruvian Andes. It has been cultivated as a food crop for centuries and is eaten locally in quantities far exceeding typical supplement doses, which is relevant context for its safety profile.

Roots are sorted by colour into yellow, red and black. These are not marketing distinctions: they represent genuinely different phenotypes with differing compound profiles, and Andean tradition assigns them to different uses. Black maca is generally associated with energy and male-oriented applications, red with prostate and female-oriented uses, and yellow is the most abundant and general purpose.

Gelatinised maca has been heat-treated to remove starch, improving digestibility for people who find raw maca powder difficult. It is not, despite the name, related to gelatin, and remains suitable for vegan use.

Maca's mechanism is poorly characterised, and this should be stated plainly rather than obscured. Its distinctive compounds are macamides and macaenes, fatty acid derivatives found essentially nowhere else, alongside glucosinolates typical of brassicas.

Notably, the trials that have measured hormones have generally found no change in testosterone, oestrogen, luteinising hormone or follicle-stimulating hormone. Whatever effects maca has on libido do not appear to be mediated by altering sex hormone concentrations, which directly contradicts how it is often marketed.

Proposed alternative routes include macamide interaction with the endocannabinoid system and effects on neurotransmitter signalling, but these remain hypotheses rather than demonstrated mechanisms in humans.

The most consistent human finding concerns self-reported sexual desire. Several small randomised trials in men have reported increases in libido measures relative to placebo, independent of hormonal change, and systematic reviews have generally described this evidence as suggestive but limited by small samples and short durations.

There is a modest body of work on sperm parameters, with some trials reporting improvements in count and motility. Work in women after the menopause has reported improvements in symptom scores in some trials, though results are inconsistent and sample sizes small.

Evidence for energy, mood, exercise performance and body composition is weak. Where positive findings exist they come from small studies that have not been robustly replicated. The overall picture is a traditional food with a handful of interesting but preliminary human findings, some way short of what its market positioning implies.

Maca has a long history of consumption as a food in quantities greatly exceeding supplement doses, and trials have reported it as well tolerated. The most common complaints are digestive: bloating, gas and discomfort, more frequent with raw powder than gelatinised.

As a brassica, maca contains glucosinolates, which in very large quantities have goitrogenic potential. This is unlikely to matter at normal supplemental intakes in someone with adequate iodine status, but people with existing thyroid conditions should be aware of it. Some users report a stimulating effect that disturbs sleep if taken late.