Maca

Is maca safe?

Probably, for healthy adults at food-like doses for a few months. Maca is the dried root of Lepidium meyenii, a cabbage-family plant that Andean farmers have eaten for centuries. LiverToxLiverToxA free US National Institutes of Health database that summarises what is known about liver injury caused by medicines, herbs and supplements.More in the glossary, the US liver injuryDrug-induced liver injuryLiver damage caused by a medicine, herbal product or supplement. It is usually rare and unpredictable, but it can be serious.More in the glossary database, has no reports of liver harm, and trials at 1.5 to 3.5 g a day report few side effects. It scores 77 here.

The weak point is how little we know. A 2011 systematic review found only four small randomised trials for menopause symptoms and concluded that safety "has not been proved yet". Our confidence is low for that reason, not because of known harm.

What do the studies show?

Most maca trials enrolled a few dozen people for 6 to 12 weeks. Reviews of the sexual function and menopause trials, from 2010 and 2011, rated the evidence as limited: too few trials, too few participants, uneven quality. MSKCC's consumer summary says no side effects have been reported, but trials this small and short can miss rare harms.

One trial stands out. In a 2008 trial, researchers gave adults with metabolic syndrome maca, yacon or silymarin for 90 days. The group on 0.6 g of maca a day had a moderate rise in diastolic blood pressure and in AST, a liver enzyme. It is one small study, but Health Canada cites it in its warning to people with blood pressure conditions.

Memorial Sloan Kettering lists subjective reports of altered menstrual cycles, moodiness, cramps, gastritis and insomnia, and one case of prolonged bleeding between periods with a high testosterone reading in a woman in her thirties taking a teaspoon of maca powder a day.

Does maca change your hormones?

Supplement labels promise "hormone balance" and higher testosterone. Blood tests do not show it in men.

The picture in women is less clear. MSKCC notes that some trials found shifts in LH and FSH and others did not, and lab extracts of maca show estrogen-like activity. Maca can also interfere with testosterone blood tests, so tell your doctor before hormone labs. Claims that it raises testosterone are not supported by the human trials that measured it.

What is in the bag?

The good news: when researchers tested 39 maca supplements from 11 companies in 2020, DNA sequencing confirmed every one was maca. Species substitution, a common problem with herbs such as echinacea, did not show up.

Three problems remain:

• Hidden drugs in sex pills. In 2017 the FDA ran Class I recalls of "MACA gold" tablets, which contained sildenafil, and of a "maca root" capsule blend that held sildenafil, desmethyl carbodenafil and tadalafil. These drugs can drop blood pressure dangerously with nitrates.
• Metals from the soil. A 2021 study of maca grown near mines in Junín, Peru found average cadmium (0.32 mg/kg) and lead (0.20 mg/kg) above FAO/WHO limits. Estimated daily intakes stayed below reference doses, but the authors flagged arsenic and cadmium cancer risk for local eaters.
• Origin and processing vary. Maca grown in China differs chemically from Peruvian maca, and raw, gelatinised and extracted products are not equivalent. Few labels say which you are buying.

FDA food recall records also show maca snacks and powders recalled for Salmonella or Listeria in other ingredients, and supplement firms recalled for failing manufacturing rules.

Who should be careful

• High blood pressure or blood thinners. Health Canada asks for a doctor's advice first at 0.6 g a day or more.
• Hormone-sensitive conditions. Breast or uterine cancer, endometriosis or fibroids: talk to your oncologist or gynaecologist.
• Anxiety or depression. Health Canada's monograph asks people with these conditions to check with a professional before using maca for mood or sexual health.
• Pregnancy and breastfeeding. No safety data.
• Anyone buying maca for erections. Skip products that promise fast results; that is the profile of a spiked pill.

How to use it more safely

Stay within 1.5 to 3.5 g of dried root a day, the range used in trials (Health Canada's monograph allows up to 3.5 g), and ask a doctor before going beyond three months, as Health Canada requires labels to say. Choose a single-ingredient powder or capsule that names the plant part and dose, ideally with heavy metal testing or a Canadian NPN. For other herbs sold for libido and testosterone, see tongkat ali.

How we scored it

Organ toxicity (85) is the strongest factor, with no liver injuryDrug-induced liver injuryLiver damage caused by a medicine, herbal product or supplement. It is usually rare and unpredictable, but it can be serious.More in the glossary on record. Regulatory actions (82), interactions (80) and dose safety (78) reflect a legal, lightly regulated food with few reported problems but thin, short-term evidence. Product quality (62) is the weakest, held back by sildenafil-spiked sex pills sold as maca and metal contamination in maca from mining areas.