Quick answer

In trials of up to about 3 months at 1.5 to 3.5 g a day, side effects were uncommon and mostly mild, such as stomach upset and headache. LiverTox rates maca an unlikely cause of liver injury. Its safety in pregnancy, while breastfeeding and over years of use has not been studied.^1,2,3

Key facts

Stomach upset was the most frequent side effect in a small dose-finding trial, reported by 31% of participants.^1,4
LiverTox describes one published case of liver injury, in a man who drank 300 mL of a maca liquor.¹
In 2019 FDA found hidden sildenafil in a product sold as Peru Maca.⁵
No safe upper amount has been set for maca.³

Side effects reported in trials

Side effects reported with maca are uncommon and usually mild, mostly stomach upset and headache.¹

Stomach upset was the most frequent side effect in a small dose-finding trial, reported by 31% of participants. In a 12-week trial in 80 men, two on maca had mild stomach complaints and kept taking it.^1,4,6

The trial record on safety is thin. A 2010 review noted that none of the four small trials it found had assessed side effects at all, and most trials were small and lasted 12 weeks or less.²

Liver and blood pressure

LiverTox rates maca an unlikely cause of liver injury. It describes one published case of jaundice in a man who drank 300 mL of a maca liquor, which cleared over 1 to 3 months.¹

In a 90-day trial in adults with metabolic syndrome, 0.6 g of maca powder a day moderately raised the liver enzyme AST and diastolic blood pressure.⁷

The blood pressure findings point in different directions: a 6-week trial in women after menopause reported lower diastolic blood pressure on maca. If you have liver disease or high blood pressure, ask your doctor before taking it.^7,8

Hormones, for men and for women

In healthy men, 1.5 or 3 g a day for 12 weeks did not change testosterone, estradiol, LH, FSH or prolactin compared with placebo.⁹

Results in women split by product. Two trials after menopause found no change in estradiol, FSH or LH, while the trials of one branded gelatinized maca reported more estradiol and less FSH. Given that split, women with endometriosis, fibroids, breast cancer or another hormone-sensitive condition should ask a doctor first.^8,10,11

Hidden drugs in products sold for sexual enhancement

FDA told consumers in 2019 not to buy or use a product sold as Peru Maca, after its laboratory found sildenafil, a prescription drug ingredient, that was not on the label.⁵

FDA says many products sold for sexual enhancement contain hidden drug ingredients, even when they are sold as dietary supplements or as all natural.¹²

FDA warns that sildenafil can interact with nitrate medicines such as nitroglycerin and drop blood pressure to dangerous levels. Be wary of any maca product sold for sexual enhancement, whatever its label lists, and report problems to FDA's MedWatch program.^5,12

Antidepressants, stimulants and birth control

No official source we checked names an interaction between maca and any medicine. The MedlinePlus pages for escitalopram, sertraline and fluoxetine list St. John's wort and tryptophan among herbal products that can interact, the page for dextroamphetamine and amphetamine lists St. John's wort, L-glutamine and tryptophan, and the page for a common birth control pill lists St. John's wort. None of them mentions maca.^{13,14,15,16,17}

That is a gap in the evidence, not proof that a combination is harmless. Two small trials gave maca to adults taking SSRI antidepressants under a psychiatrist's care and reported it was well tolerated, but they were not designed to test safety. Ask your pharmacist before combining maca with any prescription medicine.^4,18

Who should ask a doctor first

No safe upper amount has been set for maca. Trials used up to 3.5 g a day, mostly for 12 weeks or less, and a 2011 review noted that its safety had not been proven.^2,3,10

Anyone pregnant or breastfeeding, since maca has not been studied at these times
Anyone taking prescription medicines, including antidepressants, stimulants for ADHD, hormonal birth control or medicines for blood pressure
People with liver disease or high blood pressure
People with a hormone-sensitive condition
Anyone under 18

Questions people ask

Is it safe to take maca every day?

Trials gave it daily for up to about 3 months with few, mostly mild side effects. Beyond that its safety has not been studied, and no safe upper amount has been set.^1,3

Does maca have side effects for men?

The side effects reported are the same for men and women, mostly stomach upset and headache. In men, maca did not change testosterone or other reproductive hormones over 12 weeks.^1,9

Does maca have side effects for women?

Side effects in women's trials were also uncommon and mild. Women who are pregnant or breastfeeding, or who have a hormone-sensitive condition such as endometriosis, should ask a doctor first.^11,18

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Sources

This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.