Our approach
Root / adaptogen

Maca root

DWeak evidence

At a glance

Typical studied dose
1.5–3 g a dayDried root powder, usually for 6 to 12 weeks. Extract products vary too much to convert reliably.
Effect on testosterone
None measuredA 12-week randomised trial in men at 1.5 g and 3 g a day found serum testosterone unchanged at every time point.
Libido trials
4 RCTs, all smallThree of four were positive in a 2010 systematic review, which still judged the evidence too limited to be conclusive.
Menopause trials
4 RCTs, all smallAll favourable on symptom scores, but a 2011 review said numbers and quality were too low for firm conclusions.
Safety profile
Food-likeEaten as a staple in Peru. Long-term supplement safety at high doses has not been studied properly.

What is Maca root?

Maca (Lepidium meyenii) is a root vegetable in the same family as radish, cabbage and broccoli. It grows at 4,000 metres and above in the Peruvian Andes, where it has been eaten for centuries, usually boiled, baked or made into a porridge or drink. The root comes in yellow, red and black varieties, and some supplement brands sell them separately on the strength of small studies suggesting they behave differently. Most of what you find on a shelf is dried, ground root, either raw or "gelatinised". Gelatinised maca has been cooked under pressure to remove the starch, which makes it easier to digest and closer to how it is traditionally eaten. Extracts also exist, but they are not standardised to any agreed marker compound, so one brand’s 500 mg extract cannot be compared with another’s.

How it works

Nobody knows how maca works, if it does. That is worth saying plainly, because product pages often write as if the mechanism were settled. The root contains compounds called macamides and macaenes, which are unique to maca, along with glucosinolates, sterols and a lot of ordinary carbohydrate and protein. Early marketing claimed maca acted as a hormone or boosted testosterone. The human evidence contradicts that: in a 12-week trial in men it did not change testosterone, oestradiol, LH, FSH or prolactin. The current theory is that any effect on desire or mood acts somewhere other than the sex hormones, possibly in the brain, but this is a hypothesis drawn largely from animal work rather than a demonstrated pathway in people.

What the research actually shows

Evidence strength varies by what is being claimed, so each use is graded separately against the published criteria rather than averaged into one reassuring letter.

Improving sexual desire and function

CLimited evidence

This is maca’s best-supported claim, and it is still thin. A 2010 systematic review in BMC Complementary and Alternative Medicine found four randomised, placebo-controlled trials. Two reported a significant improvement in sexual desire or dysfunction, in healthy menopausal women and healthy men. One, in cyclists, found no effect. The fourth, in men with mild erectile dysfunction, reported an improvement on a standard erectile function score. The authors concluded the evidence was limited, because the trials were few, small and short. A small pilot trial in people with sexual side effects from SSRI antidepressants found a possible dose-related benefit. That is a promising signal, not a finding. The grade is C: something may be there, and a single well-run trial could confirm or erase it.

Sources: Shin BC, Lee MS, Yang EJ, Lim HS, Ernst E (2010), Dording CM et al

Easing menopausal symptoms

CLimited evidence

A 2011 systematic review in Maturitas found four randomised trials of maca in peri- and postmenopausal women. All four reported favourable effects on standard menopause symptom scores. The reviewers still concluded the evidence was limited, and they were right to: the total number of women was small, the methods were weak, and several trials came from the same group of researchers. For anyone weighing maca against treatments with a real evidence base, such as hormone therapy or the non-hormonal drugs, maca is not in the same league. Hot flushes also respond strongly to placebo, which makes small trials especially easy to over-read.

Sources: Lee MS, Shin BC, Yang EJ, Lim HJ, Ernst E (2011)

Raising testosterone

FNot supported

This is the claim to be most sceptical of, because it has actually been tested and failed. A 12-week double-blind randomised trial published in the Journal of Endocrinology gave healthy men 1.5 g or 3 g of maca a day. Serum testosterone was not affected at any time point, and neither were the other reproductive hormones measured. The same research group separately found that the men’s reported sexual desire improved without any change in testosterone. So if maca does anything for libido, it does not do it through testosterone. A product sold as a "testosterone booster" on the strength of maca is selling a mechanism the research has ruled out.

Sources: Gonzales GF et al

Improving male fertility and sperm quality

DWeak evidence

A few small trials have reported increases in semen volume, sperm count or motility with maca, and there is a larger body of animal work. The human studies are too small and too short to build a fertility decision on, and none has shown an increase in pregnancies, which is the outcome that matters. Anyone trying to conceive is better served by a fertility assessment than by a root powder, and should not use maca as a reason to delay one.

Energy, stamina and mood

DWeak evidence

Maca is widely sold as an energy food and an "adaptogen". Neither label has a scientific definition that trials can test directly, and the human studies on energy, exercise performance and mood are few, small and inconsistent. Maca is a nutritious, carbohydrate-rich vegetable, and a spoonful in a smoothie will provide calories, but that is not the same as a stimulant effect, and it does not have one.

Effective dosage

Most human trials used 1.5 to 3 g of dried maca root a day, typically for 6 to 12 weeks, and occasionally up to 3.5 g. That is roughly a heaped teaspoon to a tablespoon of powder. Capsule products often provide 500 mg to 750 mg per capsule, so matching a studied dose means three to six capsules a day. Gelatinised powder is cooked, which is closer to how maca is eaten in Peru and tends to be easier on the stomach. Effects, where reported, took weeks rather than days to appear.

Where products diverge from the research. The common gap is the capsule. A single 500 mg capsule is a third of the lowest studied dose, and many products direct one or two a day. Extracts make it harder still: a label reading "maca extract 4:1, 500 mg" is claiming to equal 2 g of root, but there is no agreed standard, and the trials mostly used whole powdered root rather than extracts. The other gap is colour. Black, red and yellow maca are sometimes sold at a premium on the basis of differences seen mainly in animal studies. There is no human evidence that justifies paying more for a particular colour.

Safety, side effects and interactions

Maca is a staple food in the Andes and has been eaten in large quantities for generations, which is reassuring. In trials lasting up to about three months, side effects were uncommon and mild, mostly stomach upset. That is not the same as knowing that high-dose, long-term use as a supplement is safe, because no one has studied it properly. Three points deserve care. First, maca is a brassica and contains glucosinolates, which in large amounts can interfere with thyroid function in people who are short of iodine. This is theoretical for most people, but anyone with thyroid disease should mention maca to their clinician, and raw powder carries more of these compounds than cooked. Second, anyone with a hormone-sensitive condition, such as some breast cancers, endometriosis or fibroids, should ask before using it. The human evidence suggests maca does not act as a hormone, but the question has not been settled. Third, there is a published case of maca interfering with a laboratory testosterone test in a woman, so tell whoever orders your blood tests that you take it. There is not enough safety data for pregnancy or breastfeeding.

None of this is medical advice. See the medical disclaimer for what that means before you act on anything here.

Common questions

Does maca increase testosterone?

No. A 12-week randomised trial gave men 1.5 g or 3 g of maca a day and found serum testosterone unchanged at every point, along with the other reproductive hormones. Some of the same men reported more sexual desire, which suggests that if maca affects libido, it does so through some route other than testosterone.

Does maca work for libido?

Possibly, a little. A 2010 systematic review found four small randomised trials, three of which reported benefits for sexual desire or function. The reviewers still concluded the evidence was too limited to be sure. If you try it, give it six to eight weeks at 1.5 to 3 g a day, which is what the trials used, and be honest with yourself about whether it made a difference.

Can maca help with menopause symptoms?

Four small trials all reported improvements in symptom scores, but a 2011 review judged the evidence limited because the trials were small and methodologically weak. Menopause symptoms respond strongly to placebo, which makes small trials easy to over-read. Maca is not a substitute for a conversation about treatments with much stronger evidence.

What is the difference between raw and gelatinised maca?

Gelatinised maca has been cooked under pressure and dried, which removes most of the starch. It is closer to how maca is eaten in Peru, where it is always cooked, and many people find it easier to digest. Raw powder keeps more of the glucosinolates, the compounds with a theoretical effect on the thyroid. For most people either is fine; gelatinised is the more cautious choice.

Is red or black maca better than yellow?

There is no good human evidence that one colour is better for any purpose. The differences come mainly from animal studies. Paying a premium for a specific colour is paying for a hypothesis.

How much maca should I take?

Human trials mostly used 1.5 to 3 g of dried root a day, which is about one to three teaspoons of powder or three to six typical capsules. A single 500 mg capsule is a third of the lowest studied amount.

Is maca safe?

For most healthy adults at food-like amounts it appears to be, and trials of up to three months reported few side effects. If you have thyroid disease or a hormone-sensitive condition, or you are pregnant or breastfeeding, check with a clinician first. Also tell whoever orders your blood tests, as maca has been reported to interfere with a testosterone assay.

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Compiled by SNL Team