Maca, a root vegetable grown in Peru, is used to enhance fertility, increase energy and stimulate the immune system, although these benefits are unproven by clinical studies. In Peru and Bolivia, people eat maca as a vegetable, but it is also available as a supplement. No harmful side effects are known. Maca supplements, however, have not undergone extensive testing in clinical trials, so their safety has not been established, NYU Langone Medical Center warns.
Thyroid Effects
Maca contains glucosinolates, compounds found in many cruciferous vegetables. If you have a thyroid condition, glucosinolates combined with a low-iodine diet can cause enlargement of the thyroid gland, called a goiter. In the United States, iodine deficiency rarely occurs because American table salt typically contains added iodine, but 40 percent of the world remains at risk for iodine deficiency.
Possible Estrogenic Activity
In a clinical study conducted by researchers from Palacký University and reported in the March 2006 issue of "Cell Biology and Toxicology," extracts of dehydrated maca exhibited estrogenic properties in laboratory studies. If you have or are at risk for developing hormone-dependent cancers such as breast, prostate or uterine cancer, do not take maca without your physician's approval.
Pregnancy and Breastfeeding
No clinical studies have been done on the effects of maca in pregnant or breastfeeding mothers, so no one knows if maca supplements are safe to take during these times. In general, the growing fetus and nursing infant are susceptible to harm from substances that might not cause side effects in adults. Don't take any supplement during pregnancy or while nursing without your doctor's approval.
Considerations
Because maca has a long, safe history of use as a food, it appears to have a low potential for toxicity, Drugs.com states. Ingesting supplements, which concentrate the active ingredients of a plant, could have different effects than just eating maca as a vegetable. If you have liver or kidney disease, which affect the way you metabolize drugs, do not take this supplement without your doctor's approval. Dried maca appears to contain lower amounts of active ingredients than fresh.
References
- Drugs.com: Maca
- NYU Langone Medical Center; Maca; February 2011
- "Cell Biology and Toxicology"; The In Vitro Biological Activity of Lepidium Meyenii Extracts; K. Valentova, et al.; March 2006
- American Thyroid Association: Iodine Deficiency
- Cornell University; Glucosinolates; March 2009
- Memorial Sloan-Kettering Cancer Center: Maca
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