Maca root: libido, menopause and fertility claims, and what is known about safety

Maca, Lepidium meyenii, is a biennial plant of the cabbage family that grows at high altitude in the Andes. The dried root has been eaten for over two thousand years. It contains protein, carbohydrate and fibre, along with compounds unique to the plant called macamides, as well as glucosinolates and polyphenols. Content varies with the colour type, where it was grown and how it was processed.

Most clinical research concerns sexual health. A review in PubMed Central describes a trial in which daily gelatinised maca for 12 weeks increased sexual desire independently of changes in mood, and another in which men with mild erectile dysfunction showed improved erectile function on a higher daily dose. These are small, short studies.

Persistent loss of desire or erection difficulty should be discussed with a GP, since causes include diabetes, heart disease, medicines, low mood, alcohol and relationship stress. Effective treatments exist, and a supplement should not delay the checks.

Several studies using gelatinised maca for 12 weeks or longer reported reduced menopausal symptom severity, with improvements in psychological symptoms and sleep disruption. The NHS offers HRT and non-hormonal approaches for menopause, and it notes that herbal remedies such as black cohosh and red clover have very little evidence on how well they work or how safe they are. Maca falls into the same cautious category.

• Heavy, irregular or post-menopausal bleeding should always be reported to a GP.

• Mood changes that affect daily life are worth raising, whatever supplements are tried.

Laboratory and animal work suggests maca might benefit sperm parameters and reproductive function under stress, but clinical evidence in people is limited, particularly for female fertility. Two studies hint at improved physical endurance, yet robust data are sparse. Couples who have been trying to conceive for a year, or sooner if the woman is older or there are known problems, should seek fertility advice rather than depend on supplements.

It is natural to ask whether maca acts on hormones. The published findings are inconsistent, especially for follicle-stimulating hormone and testosterone. Anyone with a hormone-sensitive condition, thyroid disease or who is undergoing hormone treatment should discuss maca with the specialist, since uncertain effects are harder to monitor than known ones.

Fresh maca contains high levels of glucosinolates, and traditional drying and cooking reduce them. Glucosinolate-rich brassicas have a theoretical relevance to thyroid function in large amounts, which is another reason that people with thyroid conditions should ask first.

The review describes maca as having a good safety profile, with no fatal adverse effects documented. Most studies at a few grams daily over 12 to 16 weeks reported no serious problems, and minor stomach upset occurs occasionally. Long-term human safety data remain limited.

One case report suggests possible inhibition of the liver enzyme CYP3A4, which could affect how certain medicines are handled, including some antidepressants, so a pharmacist should be told. The NHS advises checking with a pharmacist before taking a herbal medicine alongside prescribed drugs. Commercial maca products vary considerably in standardisation, which means the dose in a capsule may not match the dose in a trial.

Pregnancy and breastfeeding safety have not been established, and the NHS does not recommend herbal medicines in either. In the UK, maca is generally sold as a food supplement, and it is not assessed for effectiveness. The MHRA has observed that most herbal products on the market are unlicensed and that quality differs, and the NHS cautions against buying unlicensed herbal medicines online.