Maca Side Effects and Cautions

Short answer. In the sources we read, maca (Lepidium meyenii Walp., family Brassicaceae [1]) has few documented harms. LiverTox says it has not been implicated in liver injury. [2] A 12-week trial of 175 people reported no serious adverse effects. [3] But a systematic review of menopause trials noted that its safety "has not been proved yet", and the trials were small and short. [4] For several groups, including pregnancy, breastfeeding and children, Proper evidence not found.

Before you start. This is information, not medical advice. Maca is also a food. [2] Supplements are a different thing: concentrated extracts, powders and capsules vary. Ask a pharmacist or clinician if you take regular medicines. See How medicine interactions work. If you have trouble breathing or swelling of the face after taking any supplement, call 911.

What is documented

Signals to know about

• Blood pressure. In a 6-week pilot in 29 postmenopausal women, diastolic blood pressure fell after maca. [6] That was a benefit in the study, but if you take blood pressure medicine, ask a pharmacist before adding maca. No source we read tested maca with blood pressure drugs.
• Blood sugar. In the 175-person trial, black maca reduced blood glucose levels. [3] If you use diabetes medicines, tell your prescriber.
• Hemoglobin. Black maca, and in smaller proportions red maca, reduced hemoglobin only in people living at high altitude whose levels were abnormally high. [3] People living at low altitude were not affected. [3] If you have a blood condition or high-altitude symptoms, ask a clinician.
• Antidepressants. In a review of adverse-event reports about adaptogens combined with antidepressants, maca was linked to one report: restless legs syndrome with mianserin. [7] That review identified 30 reports across all the adaptogens it covered, so this is a single case, not a pattern. [7]
• Thyroid. Proper evidence not found that maca affects the thyroid. We searched PubMed for maca with thyroid, goitrogens and glucosinolates and found nothing relevant. The 29-woman pilot measured TSH and saw no difference between maca and placebo over 6 weeks. [6] That is a short, small result. If you have a thyroid condition, see thyroid problems and fatigue.
• Hormones. Two small trials in postmenopausal women found no change in estradiol, FSH or sex hormone-binding globulin. [8][6] The sources we read do not say whether maca is safe for hormone-sensitive conditions; ask a clinician. See Maca for libido, energy and menopause.

Groups for extra caution

• Pregnancy and breastfeeding: Proper evidence not found. We searched PubMed for maca with pregnancy or lactation and for a LactMed entry and found none. A review noted safety is not proved. [4] See pregnancy and breastfeeding.
• Children and teens: Proper evidence not found. See children and teens.
• Kidney disease, allergy and surgery: not described in the sources we read. That is not proof of safety. Tell the surgical team about any supplement (supplements before surgery).
• Older adults and people taking many medicines: no maca-specific information in the sources we read, so a pharmacist review is sensible.

Contamination and quality

A study of maca grown in mining-influenced areas of central Peru measured heavy metals in soil and maca hypocotyls. [9] It found estimated daily intakes below the oral reference dose for each metal, but calculated cancer risks for arsenic and cadmium above the tolerable limit in children and adults. [9] Residents of one district would be more exposed to arsenic and cadmium from eating maca. [9] The authors called for continuous monitoring. [9] This is one study of specific growing areas, not a finding about any product on a shelf. Still, it is a reason to prefer products with third-party testing information; see quality testing and certifications.

Forms matter

Trials used powdered maca, gelatinized maca, dry extract and spray-dried red or black extracts, so a safety finding for one form does not transfer to another. [8][10][3] LiverTox describes maca as a vegetable and food as well as a traditional herbal medicine. [2]