Maca root is generally well tolerated, but several groups of people should avoid it or use it only with medical guidance. The biggest concerns involve hormone-sensitive conditions, thyroid problems, pregnancy, and contamination risks from poorly sourced supplements.
People With Hormone-Sensitive Conditions
Maca exhibits estrogenic activity in lab studies, meaning it can mimic or influence estrogen in the body. Memorial Sloan Kettering Cancer Center specifically warns people with hormone-sensitive cancers, such as breast cancer or uterine cancer, that maca may interfere with treatment. The same caution applies to anyone with endometriosis or uterine fibroids, conditions that are fueled by estrogen.
In a clinical trial of 34 postmenopausal women taking 500 mg of pre-gelatinized maca daily for four months, researchers measured increases in estradiol (the body’s primary form of estrogen) along with decreases in other hormones like FSH and LH. That hormonal shift is exactly what makes maca appealing for menopause symptoms, but it’s also why the supplement can be problematic if you have a condition where rising estrogen levels would cause harm.
People With Thyroid Disorders
Maca belongs to the Brassicaceae family, the same plant family as broccoli, cabbage, and kale. Like its relatives, maca contains glucosinolates, sulfur-rich compounds that can break down into substances known to interfere with iodine uptake in the thyroid gland. These are sometimes called goitrogens because, in large enough amounts, they can contribute to goiter or worsen existing thyroid dysfunction.
The clinical trial mentioned above also found that maca supplementation led to a decrease in T3, one of the thyroid hormones your body depends on for metabolism and energy regulation. If you have hypothyroidism, Hashimoto’s disease, or any condition where your thyroid is already underperforming, adding a goitrogen-containing supplement could compound the problem. People taking thyroid medication should be especially cautious, since maca could potentially work against what the medication is trying to do.
Pregnant or Breastfeeding Women
There is no reliable safety data on maca use during pregnancy or breastfeeding. While maca has been consumed as a food in Peru for centuries, the concentrated supplement forms sold today deliver much higher doses of active compounds than you’d get from eating the root as part of a traditional diet. Without clinical trials confirming safety for a developing fetus or nursing infant, the standard guidance is to avoid maca supplements during both pregnancy and breastfeeding.
People Sensitive to Digestive Upset
Raw maca powder retains the full starch content of the dried root, including resistant starches that your small intestine can’t fully break down. For some people, this leads to gas, bloating, or loose stools, particularly at higher doses. If you have irritable bowel syndrome or a sensitive stomach, raw maca is more likely to cause problems.
Gelatinized maca, which is pre-cooked using heat and pressure, has most of this starch removed. It tends to be much easier on the digestive system while preserving the key active compounds. If you’ve tried maca and had stomach trouble, the form matters: switching from raw to gelatinized often resolves the issue. But if you have significant digestive conditions, even gelatinized maca may not sit well.
Side Effects to Be Aware Of
In a clinical trial testing maca at doses of 1.5 g and 3.0 g per day in 20 patients, the most common side effects were digestive upset (reported by 5 of 16 participants who completed enough of the study to be evaluated), headache, and irritability. Less common effects included sleep disruption, increased sweating, panic attack, blurry vision, and increased dreaming. One participant experienced a fibromyalgia flare-up, and another reported thicker menstrual discharge. All of these effects were transient, and none caused anyone to stop the study.
That said, if you already deal with anxiety, panic disorder, or chronic insomnia, the reported cases of panic attacks and sleep disruption are worth noting. Maca has energizing properties, and some people find it overstimulating, especially when taken later in the day.
Heavy Metal Contamination Risk
This one applies to everyone, but especially to people who take maca long-term. Maca roots can accumulate toxic metals from the soil where they’re grown. Peru’s mining industry has contaminated some growing regions, and naturally high mineral concentrations from volcanic soil formation add to the problem. Studies analyzing yellow and purple maca have found that both cadmium and lead concentrations in the roots exceeded permissible safety limits. Zinc levels were also elevated.
This doesn’t mean all maca products are contaminated, but it does mean quality control matters enormously. Look for products that provide third-party testing for heavy metals on a per-batch basis. Anyone with chronic kidney disease or liver conditions should be particularly wary, since their bodies are less equipped to clear toxic metals efficiently. Children are also more vulnerable to heavy metal exposure relative to their body weight.
Safe Dosage Range
Most clinical studies have used doses between 1.5 g and 3.0 g per day. In the dose-finding study referenced above, 3.0 g per day was the highest dose approved by the institutional review board based on available safety data. The treatment was generally well tolerated at both doses. Researchers noted that given how much maca is consumed in traditional South American diets, higher doses are likely safe, but formal evidence supporting anything above 3 g per day is limited.
If you’re new to maca, starting at the lower end (around 1.5 g per day) lets you gauge how your body responds before increasing. People taking medications for blood pressure, diabetes, or hormonal conditions should be cautious about adding maca without knowing how it might interact with their treatment, since its hormonal and metabolic effects are real even if they tend to be mild in healthy people.