The short version
- A systematic review searching 17 databases found only four randomised controlled trials of maca for sexual function, and concluded the evidence was too limited to draw firm conclusions.
- In a 12-week trial of 1,500mg and 3,000mg maca in men aged 21 to 56, self-reported sexual desire improved from week eight while serum testosterone and oestradiol were no different from placebo.
- In 14 postmenopausal women taking 3.5g a day for six weeks, Greene Climacteric Scale anxiety, depression and sexual dysfunction scores improved with no change in estradiol, FSH, LH or SHBG.
- In the only athletic trial, eight trained cyclists improved their 40km time trial versus their own baseline (P=0.01) but not versus placebo after supplementation, while sexual desire improved against both.
- Three separate maca trials measured sex hormones and none found a change, so maca is not supported as a testosterone booster.
Maca sits in two aisles at once. On one shelf it is a libido product. On the other it is an energy product, usually with a line about Andean farmers and altitude. Only one of those shelves has randomised trials underneath it, and it is not the one with the mountains on the label.
Start with the review, because it is unusually blunt
Shin and colleagues searched 17 databases and found exactly four randomised controlled trials of maca for sexual function. Two suggested a significant positive effect on sexual dysfunction or sexual desire — one in healthy menopausal women, one in healthy adult men. One failed to show any effect in healthy cyclists. A fourth, in men with erectile dysfunction, showed significant effects on a standard index.
Their conclusion is worth quoting in spirit: the evidence is limited, and the total number of trials, total sample size and average methodological quality were too limited to draw firm conclusions.
That is a weak file. It is still a stronger file than the one behind the energy claim.
The men's trial, and the finding that kills the testosterone story
Gonzales and colleagues ran a 12-week double-blind placebo-controlled parallel trial in men aged 21 to 56, comparing 1,500mg and 3,000mg of gelatinised maca against placebo. Self-perceived sexual desire improved from eight weeks.
And then the part that almost never makes it onto a product page: serum testosterone and oestradiol were not different between the maca groups and placebo. Logistic regression showed the effect on desire was independent of testosterone, of oestradiol, and of Hamilton scores for depression and anxiety.
So whatever maca is doing, it is not doing it by raising testosterone. Anyone selling it as a hormone booster is either not reading the trial they are citing or hoping you will not.
The women's trial, at its actual size
Brooks and colleagues gave 3.5g a day of powdered maca or placebo for six weeks each, crossover, to fourteen postmenopausal women. Serum estradiol, FSH, LH and SHBG did not move. Greene Climacteric Scale scores fell significantly in the psychological subscales — anxiety and depression — and in measures of sexual dysfunction. Yeast-based reporter assays found no physiologically significant oestrogenic or androgenic activity in maca extracts up to the equivalent of 200mg/mL.
Fourteen women. That is a pilot, and the authors call the findings preliminary. It is also the second independent demonstration that maca does something to how people feel without touching the hormones it is marketed on.
Now the energy claim
The trial that gets cited for performance is Stone and colleagues, 2009: eight trained male cyclists, 14 days of maca extract or placebo, 40km time trials before and after, crossover.
Read the result carefully. Maca significantly improved 40km time-trial performance compared with the participants' own baseline (P=0.01), but not compared with the placebo trial after supplementation (P>0.05). Sexual desire improved against both baseline and placebo. In other words: in the one athletic trial, the performance effect did not beat placebo, and the libido effect did.
Eight cyclists cannot settle anything either way. But it is telling that the study most often used to support maca-for-energy is a study in which the energy outcome failed its placebo comparison and the desire outcome passed it.
What we would actually say
Buy maca for the claim that has trials, or do not buy it. On present evidence that claim is about libido and mood, in doses of roughly 1.5 to 3.5 grams a day, over eight to twelve weeks — not a fortnight. Do not buy it expecting a hormonal change; three separate trials looked and found none.
If what you are actually chasing is an afternoon energy dip, maca is a poor first move and the evidence says so plainly. Sleep hours and caffeine timing outrank it. Among botanicals with fatigue outcomes specifically, Panax ginseng has the larger literature, and even there the effect sizes are small.
We sell maca. We would rather you bought it for the right reason and judged it on the right timeline than bought it for energy and concluded that botanicals do not work.
Good questions
Does maca boost testosterone?
No. The 12-week trial most often cited for maca measured serum testosterone and oestradiol directly and found no difference from placebo, and a crossover trial in postmenopausal women found no change in estradiol, FSH, LH or SHBG. Whatever maca does, it does not appear to work through sex hormones, and any label claiming otherwise is not describing the trials.
Will maca give me more energy?
Probably not in the way the marketing implies. The one performance trial, in eight trained cyclists, improved times against the participants' own baseline but not against placebo. There is no body of randomised evidence supporting maca as a daytime energy product. The claim with actual trials behind it is about libido and mood.
How long does maca take to work?
Eight to twelve weeks in the trials that found anything. The men's trial saw improvement in sexual desire from week eight, and the women's crossover ran six weeks per arm. Two weeks is the length of the athletic pilot, and it is not long enough to judge. If you are going to try it, commit to a proper window and then decide.
What dose of maca was actually studied?
1,500mg or 3,000mg a day of gelatinised maca in the men's trial, and 3.5g a day of powdered maca in the postmenopausal trial. Those are grams, not milligrams, which matters when you are reading a blend that contributes a few hundred milligrams and cites these studies.
Is maca worth the money?
It depends entirely on what you are buying it for. For libido and mood, the evidence is limited but real and the safety record in these trials was unremarkable. For energy, performance or testosterone, we would tell you to keep your money. A brand that sells you maca for the third reason is trading on the first.
Is maca safe?
The trials reviewed reported no serious problems at these doses over six to twelve weeks, but they were small and short, so long-term safety data are thin. It is a cruciferous root, so people with thyroid conditions sometimes ask about goitrogens; that is a question for your clinician rather than a comment section, especially if you are already being monitored.
Sources
- Shin BC, Lee MS, Yang EJ, Lim HS, Ernst E. Maca (L. meyenii) for improving sexual function: a systematic review. BMC Complement Altern Med, 2010. View study
- Gonzales GF, Córdova A, Vega K, Chung A, Villena A, et al. Effect of Lepidium meyenii (MACA) on sexual desire and its absent relationship with serum testosterone levels in adult healthy men. Andrologia, 2002. View study
- Brooks NA, Wilcox G, Walker KZ, Ashton JF, Cox MB, Stojanovska L. Beneficial effects of Lepidium meyenii (Maca) on psychological symptoms and measures of sexual dysfunction in postmenopausal women are not related to estrogen or androgen content. Menopause, 2008. View study
- Stone M, Ibarra A, Roller M, Zangara A, Stevenson E. A pilot investigation into the effect of maca supplementation on physical activity and sexual desire in sportsmen. J Ethnopharmacol, 2009. View study
These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.
