Maca root is generally safe for most adults. Clinical trials using doses of 1.5 to 3 grams daily for up to 12 weeks consistently show low toxicity and good tolerance, with adverse effects being rare. That said, there are a few specific concerns worth knowing about, particularly around thyroid health, hormone-sensitive conditions, and contamination in products grown near mining regions.
What Clinical Trials Show About Side Effects
Across multiple human studies, maca produces very few reported side effects. Most participants tolerate it well at typical supplement doses of 1.5 to 3 grams per day. The most commonly noted issues are mild digestive discomfort, which tends to be more of a problem with raw maca powder than with processed forms.
Serious adverse events are extremely rare but not zero. The medical literature documents two notable case reports: unexplained vaginal bleeding in a 24-year-old woman and a manic episode in a 27-year-old man with no prior psychiatric history. These are isolated cases, not patterns, but they’re worth flagging because they suggest maca can occasionally produce unexpected effects in certain individuals.
Does Maca Change Your Hormones?
One of the most common concerns about maca is whether it throws your hormones out of balance. A 12-week randomized, placebo-controlled trial in healthy men aged 21 to 56 measured testosterone, estrogen, luteinizing hormone, follicle-stimulating hormone, and prolactin at multiple time points throughout the study. Maca had no effect on any of these hormones at either the 1.5 g or 3 g daily dose. Testosterone levels, specifically, were completely unaffected.
The picture is slightly more complicated for women. Studies using 2 grams of gelatinized maca daily in women found shifts in estradiol (a form of estrogen), with some studies showing an increase and others showing mixed results. Maca appears to influence the hormonal signaling chain between the brain and the ovaries, which means its effects may vary depending on your baseline hormone levels and where you are in your reproductive life. If you have an estrogen-sensitive condition like certain types of breast cancer, endometriosis, or uterine fibroids, this hormonal activity is something to take seriously and discuss with your doctor before supplementing.
Thyroid Concerns: The Goitrogen Factor
Maca belongs to the same plant family as broccoli, kale, and cauliflower, and like those vegetables, it contains goitrogens. These are naturally occurring compounds that can interfere with how your thyroid produces hormones, particularly if your iodine intake is already low.
The good news is that goitrogens break down with heat and moisture. Gelatinized maca, which has been cooked and processed before being dried into powder, has significantly lower goitrogen content than raw maca. If you have a thyroid condition or are concerned about thyroid function, choosing gelatinized maca over raw is a practical way to reduce your exposure. Some clinical studies have actually found that certain maca preparations had a modest positive effect on T3 (a key thyroid hormone), though this area still has limited data.
Raw vs. Gelatinized Maca
This distinction matters more than most supplement labels suggest. Raw maca powder is simply dried and ground root. It retains all of its natural starch content, which can be hard on your stomach, and it keeps its full goitrogen load. Gelatinized maca has been heated under pressure, which breaks down the starches and deactivates goitrogens. Despite the name, it contains no gelatin and is still plant-based.
If you experience bloating, gas, or stomach cramps from maca, switching to a gelatinized form often solves the problem. It’s also the form used in most clinical trials, which means the safety data we have is largely based on gelatinized products rather than raw powder.
Drug Interaction Risk Is Low
A laboratory study evaluating 30 commonly used botanical supplements tested maca’s potential to interfere with two major enzyme systems your body uses to metabolize drugs. Maca showed no significant activity on either pathway. This means it’s unlikely to speed up or slow down how your body processes common medications, including those broken down by the liver’s primary detoxification enzymes. Among the 30 botanicals tested, maca was in the group considered not likely to pose any meaningful herb-drug interaction risk.
Heavy Metals in Maca Products
This is a less-discussed but genuinely important safety issue. Maca grows almost exclusively in the central highlands of Peru, and some of those regions are near active or former mining sites. A study measuring heavy metals in maca grown at three different Peruvian locations found that cadmium and lead levels frequently exceeded the limits set by the World Health Organization and the Food and Agriculture Organization.
The permissible limit for both cadmium and lead in food is 0.1 mg/kg. Maca samples from one site (Ondores) averaged 0.46 to 0.51 mg/kg of cadmium and 0.24 to 0.28 mg/kg of lead, roughly four to five times the safe limit for cadmium and two to three times for lead. Samples from a cleaner site (JunÃn) came in at or near the permissible limits. The takeaway: where your maca was grown matters a lot. Look for products from brands that publish third-party heavy metal testing results, and be cautious about buying the cheapest option available.
Pregnancy, Breastfeeding, and Children
There is no reliable clinical data on maca’s safety during pregnancy or breastfeeding. While maca has been eaten as a food in Peru for centuries, the concentrated supplement form delivers much higher doses than you’d get from traditional cooking. Without controlled studies in pregnant or nursing women, there’s no way to confidently assess the risk. In Peru, maca is consumed as a whole food (often boiled), which is different from taking concentrated extract capsules.
Typical Dosing in Studies
Most clinical trials have used between 1.5 and 3 grams of gelatinized maca powder per day, taken for periods ranging from 6 to 12 weeks. These are the doses where we have the best safety data. Some traditional uses involve much higher amounts (up to 20 grams per day as a food), but those quantities haven’t been rigorously studied in controlled settings. If you’re new to maca, starting at the lower end of the studied range, around 1.5 grams daily, gives you a reasonable starting point with the most safety evidence behind it.