Fact checked by Rebecca Thornton, M.S., Food Science and Human Nutrition
You added maca root to your smoothie or your supplement shelf because friends keep talking about it. Then you searched for side effects and found warnings about hormones, your thyroid, and pregnancy.
On top of that, the store shelf has black maca, red maca, and yellow maca, and nobody explains whether the color changes anything.
This guide clears that up. You'll see what human studies actually found, how much they used, who should check with a doctor first, and what the research does and doesn't say about each color.
Quick answer: what are the side effects of maca root?
In human trials, maca root side effects have been rare and mild. In the largest trial, 175 adults took 3 grams a day of black or red maca extract for 12 weeks. No serious side effects were reported, no one dropped out because of side effects, and blood pressure did not change compared with a placebo [1]. Smaller trials in men and women also found maca well tolerated [2, 4, 5].
The cautions worth knowing about are:
- Pregnancy and breastfeeding. We found no human studies in these groups, so safety is unknown.
- Blood pressure and blood sugar medicine. Maca lowered diastolic blood pressure in one small trial [5], and black maca lowered blood sugar a little in another [1]. That could add to the effect of medicine for either.
- Stomach upset. People mostly report this with raw maca powder. That fits with how maca is traditionally eaten, which is cooked [7].
- Taking more than studies used. Trials used about 1.5 to 3.5 grams a day for 6 to 12 weeks [1, 2, 4, 5]. Beyond that range, and beyond a few months, there is little data.
First, black vs. red vs. yellow maca: what's the difference?
Before we get into side effects, let's clear up the color confusion. It matters because many articles give one color credit for research done on another.
Black, red, and yellow maca are all the same plant, Lepidium meyenii. You may also see it labeled Lepidium peruvianum. The color is the outer skin of the root. Farmers in the Peruvian Andes grow the colors together, and then sort them after harvest. They are not different species, and they are not different strengths.
The colors do differ in their mix of natural plant compounds. When researchers grew several colors side by side in Peru, each color had its own pattern of compounds. For example, yellow maca was higher in one compound called macaene, and a purple type was higher in another group called macamides [8]. The researchers concluded that color "has to be considered" in maca production [8].
Here is what that means for you, color by color:
| Color | What you should know | Human research on this color | Animal research only |
|---|---|---|---|
| Yellow maca (sometimes called cream) | The color you'll see most often in stores and in "regular" maca powder. | We found no human trial that tested yellow maca by name. Most early human trials didn't say which color they used [2, 3, 4]. | In rats, yellow maca had a moderate effect on sperm production [9]. |
| Red maca (sometimes called purple) | Often marketed to women, but men take it too. | In a 12-week trial that tested red and black maca side by side, red maca scored higher for mood and energy than black [1]. | In the same rat study, red maca had no effect on sperm production [9]. |
| Black maca | Less common than yellow. Often sold for men, but women take it too. | In the same 12-week trial, black maca also improved mood and energy, though less than red. The black maca group had slightly lower blood sugar [1]. | In rats, black maca had the strongest effect on sperm production of the three colors [9]. |
Do the colors have different side effects? No study has shown that. In the one trial that tested black and red maca in people, both were well tolerated [1]. Yellow maca hasn't been tested by name, but the general maca trials, where color wasn't reported, were also well tolerated [2, 4, 5].
One more thing: the rat findings are the source of a lot of "black maca is for men" marketing. Rat results don't always carry over to people, so treat them as early clues, not proof.
Want the longer comparison, including taste and how each color is used? Read Are You Taking the Right Type of Maca?
Raw vs. gelatinized maca: which is easier on your stomach?
This difference matters more for side effects than color does.
- Raw maca is dried and ground. It still has all of its starch.
- Gelatinized maca is cooked first, which breaks down much of the starch, and then dried and ground. Despite the name, it contains no gelatin.
In the Andes, people traditionally eat maca cooked, often boiled, not raw [7]. Many people say gelatinized maca sits better in their stomach. To be clear, that comes from personal reports and tradition, not from a trial that compared the two. Still, if raw powder gives you bloating or gas, switching to gelatinized maca is a simple first step.
Are there maca root side effects for women?
Trials in women have not found side effects that are specific to women. A common worry is that maca acts like estrogen. In a trial of 14 women after menopause who took 3.5 grams a day for 6 weeks, levels of estrogen and related hormones did not change [4]. A second 6-week trial in 29 women after menopause used 3.3 grams a day. The main change the researchers reported was a small drop in diastolic blood pressure [5].
The big unknowns for women are pregnancy and breastfeeding. See the next section.
If maca is part of a bigger plan for stress and energy, our guide on women's stress and energy swings covers where it fits.
Is maca safe during pregnancy or breastfeeding?
We don't know. We found no human studies on maca in pregnancy or while nursing. That doesn't mean it is harmful. It means no one has tested it. Maca is a food in Peru, but supplements give much larger amounts than most diets do.
The safest choice is to skip maca supplements while you're pregnant, trying to get pregnant, or breastfeeding, unless your provider says otherwise.
Are there maca root side effects for men? Does it change testosterone?
Trials in healthy men have not found side effects of concern. Men often ask whether maca pushes testosterone up or down. In two 12-week trials, men took 1.5 or 3 grams a day of gelatinized maca. Testosterone and other reproductive hormones did not change [2, 3]. In the first of those trials, men reported more sexual desire starting at week 8, with testosterone unchanged [2].
So maca doesn't appear to work by raising testosterone. For the full picture on that question, read Do Testosterone Boosters Work?
Can maca affect your thyroid?
There is no human evidence that it does. Here is where the worry comes from. Maca is in the same plant family as cabbage and broccoli [8]. Plants in this family contain natural compounds called glucosinolates, and maca has them too [8]. Very large amounts of some cabbage-family foods have raised thyroid questions over the years.
But we found no human studies showing that maca changes thyroid function. If you take thyroid medicine, it's still smart to tell your provider before you start, so they can keep an eye on your usual lab work.
Can maca raise blood pressure?
The studies point the other way. In the 175-person trial, blood pressure did not change compared with placebo [1]. In the smaller trial of 29 women, diastolic blood pressure dropped a little [5]. If you take blood pressure medicine, that small drop is the reason to check with your provider first.
Who should talk to a doctor before taking maca?
If any row below fits you, bring the label to your provider or pharmacist before you start.
| If you... | Why it matters | How strong is the evidence? |
|---|---|---|
| Are pregnant, trying to get pregnant, or breastfeeding | No human safety studies exist for these groups. | No data |
| Take blood pressure medicine | Diastolic blood pressure dropped a little in one small trial [5]. A larger trial saw no change [1]. | Small trials, mixed results |
| Take medicine that lowers blood sugar | The black maca group had slightly lower blood sugar after 12 weeks [1]. | One human trial |
| Take thyroid medicine | Maca contains glucosinolates, like other cabbage-family plants [8]. No human thyroid studies exist. | Theory only |
| Have a health condition affected by hormones, or take hormone therapy | Trials found hormone levels didn't change in healthy people [3, 4], but people with these conditions weren't studied. | Not studied in this group |
| Are under 18 | Trials only included adults. | No data |
How much maca per day did the studies use?
Most trials used between 1.5 and 3.5 grams of maca a day, for 6 to 12 weeks. Here are the ones this article draws on:
| Who | Amount per day | How long | Color | What happened |
|---|---|---|---|---|
| Healthy men [2, 3] | 1.5 g or 3 g, gelatinized | 12 weeks | Not reported | Well tolerated. Reproductive hormones unchanged. |
| 14 women after menopause [4] | 3.5 g | 6 weeks | Not reported | Well tolerated. Estrogen and related hormones unchanged. |
| 29 women after menopause [5] | 3.3 g | 6 weeks | Not reported | Well tolerated. Diastolic blood pressure slightly lower. |
| 175 adults [1] | 3 g of extract | 12 weeks | Black or red | No serious side effects. No blood pressure change vs. placebo. |
The capsule math
Labels are written in capsules and scoops, but studies are written in grams. Here's how to translate:
- Our Organic Gelatinized Black Maca gives 1 gram in 2 capsules.
- The label says 2 capsules, 1 to 2 times a day with food. That is 1 to 2 grams a day, which sits at or below the amounts trials used.
- If you also use maca powder in smoothies, add it up. Powders vary, so check the grams per scoop on your label.
What we don't know yet: how maca behaves at higher amounts, or over many months or years. Staying within the studied range is the simplest way to stay on solid ground.
How long does maca take to work?
Give it at least 6 to 8 weeks before you judge it. In the trials above, changes were measured at 6 to 12 weeks [1, 2, 4, 5]. In one trial in men, the change in sexual desire showed up at week 8, not before [2]. In the red vs. black trial, most results were measured at week 12 [1].
That means feeling nothing in week one is normal, and it's not a reason to double the dose.
How strong is the maca safety research? An evidence check
| Question | What the evidence says | Type of evidence |
|---|---|---|
| Is maca safe for healthy adults short term? | Yes, at 1.5 to 3.5 g a day for up to 12 weeks [1, 2, 4, 5] | Human trials |
| Does it change reproductive hormones? | Not in healthy men or in women after menopause [2, 3, 4] | Small human trials |
| Does color change safety? | No difference seen between black and red [1]. Yellow not tested by name. | One human trial |
| Is it toxic? | Low toxicity in animal and lab studies [6] | Animal and lab |
| Pregnancy and breastfeeding? | Unknown | No studies found |
| Thyroid? | No human evidence of an effect | Theory only |
| Long-term use (over a year)? | Unknown | No long-term trials found |
The limits are real. Most maca trials are small, short, and done by a handful of research groups. That's why we tell you what the studies measured instead of promising results.
What about the side effects people post online?
On forums, people describe feeling wired, sleeping poorly, getting breakouts, or having stomach trouble after starting maca. These are personal stories, not study results, and the trials above did not report them as problems [1, 2, 4, 5]. But trials are small, and everyone reacts differently. If you notice any of these, lower your amount, take it earlier in the day, or stop and see if it goes away.
6 mistakes that make maca side effects more likely
- Starting at the top dose. Begin at the low end and build up over two weeks.
- Taking raw powder on an empty stomach. Take maca with food, and try gelatinized if raw bothers you.
- Stacking maca without counting. Smoothie powder, capsules, gummies, and "blend" products can all contain maca. Add up the grams.
- Taking it late in the day. If maca makes you feel alert, take it in the morning or at lunch.
- Doubling up in week one. Trials measured results at 6 to 12 weeks. More maca won't speed that up.
- Believing the color hype. A label that says "black maca for men" or "red maca for women" is marketing unless it points to a human study on that color.
Starting maca? Try a 2-week check-in
| When | What to do | What to watch for |
|---|---|---|
| Days 1 to 7 | Take about 1 gram a day (2 of our capsules) with breakfast or lunch. | Stomach comfort, sleep, and whether you feel jittery |
| Days 8 to 14 | If you feel fine, you can move to 2 grams a day, split between two meals. | The same three things. Stay at 1 gram if anything feels off. |
| Week 6 to 8 | Check in with yourself. Jot down energy and mood on a 1 to 10 scale once a week from day 1 so you can compare. | Whether it's worth continuing for you |
Stop and call your provider if you get a rash, swelling, trouble breathing, or any reaction that worries you.
Key takeaways
- Maca root side effects in human trials have been rare and mild at 1.5 to 3.5 grams a day for up to 12 weeks.
- Black, red, and yellow maca are the same plant. Color changes the mix of plant compounds, not the species.
- In the only human trial comparing colors, red maca beat black for mood and energy, and both were well tolerated.
- "Black maca is best for sperm" comes from rat studies, not human ones.
- Trials haven't shown maca changing testosterone or estrogen levels in healthy people.
- Skip maca during pregnancy and breastfeeding, since it hasn't been studied.
- Check with your provider first if you take blood pressure, blood sugar, thyroid, or hormone medicine.
- Gelatinized maca is cooked before drying, which many people find easier to digest than raw.
Frequently asked questions
What are the side effects of maca root?
In human trials, side effects have been rare and mild at 1.5 to 3.5 grams a day for up to 12 weeks. Some people report stomach upset, mostly with raw powder, and online reports mention feeling wired or sleeping poorly. Pregnancy, breastfeeding, and some medicines are the main reasons to check with a provider first.
Are there maca root side effects for women?
Trials in women after menopause found maca well tolerated, and estrogen and related hormones did not change. Safety in pregnancy and breastfeeding has not been studied, so it's best to skip maca during those times unless your provider says otherwise.
Are there maca root side effects for men?
Trials in healthy men found maca well tolerated at 1.5 or 3 grams a day for 12 weeks. Testosterone and other reproductive hormones did not change.
Is maca safe during pregnancy?
No one knows, because it hasn't been studied in pregnancy or breastfeeding. The safest choice is to avoid maca supplements while pregnant, trying to conceive, or nursing, unless your provider approves.
How much maca per day is safe?
Human trials used about 1.5 to 3.5 grams a day for 6 to 12 weeks without serious side effects. Start at the low end, take it with food, and talk with your provider before going above what studies used.
Does black maca have more side effects than red or yellow maca?
No study has shown that. In the one human trial that tested black and red maca side by side, both were well tolerated for 12 weeks. Yellow maca hasn't been tested by name, but general maca trials were also well tolerated.
What is the difference between black, red, and yellow maca?
They are the same plant, Lepidium meyenii, with different root skin colors. Each color has a slightly different mix of plant compounds. In one human trial, red maca scored higher than black for mood and energy. Yellow is the most common color in stores.
Can maca affect your thyroid?
There is no human evidence that it does. Maca contains glucosinolates, like cabbage and broccoli, which is where the worry comes from. If you take thyroid medicine, tell your provider before starting.
How long does maca take to work?
Trials measured changes at 6 to 12 weeks. In one trial in men, changes showed up at week 8 and not earlier. Give it at least 6 to 8 weeks before deciding.
How we make our black maca
Our Organic Gelatinized Black Maca is USDA Organic, grown in Peru, and gelatinized to remove excess starch. It's third-party tested for purity and authenticity, including mold and microbes. It has no fillers, binders, or preservatives.
We chose black maca, and we'll be straight with you about the research: in the one human trial that compared colors, red maca did a bit better on mood and energy [1]. We still think black maca is a great daily choice, and we'd rather you choose it knowing exactly what the science says.
Not sure how to judge any supplement label? Our guide on how to read a supplement label like an expert walks you through it.
Your next step
If you're healthy, not pregnant or nursing, and not on the medicines listed above, maca is one of the better-tolerated supplements studied. Start low, take it with food, and give it 6 to 8 weeks. Ready to try it? Start with 2 capsules of Organic Gelatinized Black Maca with breakfast, and use the 2-week check-in above. Curious about the benefits side? Read What Are the Benefits of Maca Root?
Sources
- Gonzales-Arimborgo, C., Yupanqui, I., Montero, E., et al. (2016). Acceptability, safety, and efficacy of oral administration of extracts of black or red maca (Lepidium meyenii) in adult human subjects: A randomized, double-blind, placebo-controlled study. Pharmaceuticals, 9(3), 49. PubMed
- Gonzales, G. F., Córdova, A., Vega, K., et al. (2002). Effect of Lepidium meyenii (MACA) on sexual desire and its absent relationship with serum testosterone levels in adult healthy men. Andrologia, 34(6), 367-372. PubMed
- Gonzales, G. F., Cordova, A., Vega, K., et al. (2003). Effect of Lepidium meyenii (Maca), a root with aphrodisiac and fertility-enhancing properties, on serum reproductive hormone levels in adult healthy men. Journal of Endocrinology, 176(1), 163-168. PubMed
- Brooks, N. A., Wilcox, G., Walker, K. Z., et al. (2008). Beneficial effects of Lepidium meyenii (Maca) on psychological symptoms and measures of sexual dysfunction in postmenopausal women are not related to estrogen or androgen content. Menopause, 15(6), 1157-1162. PubMed
- Stojanovska, L., Law, C., Lai, B., et al. (2015). Maca reduces blood pressure and depression, in a pilot study in postmenopausal women. Climacteric, 18(1), 69-78. PubMed
- Valerio, L. G., Jr., & Gonzales, G. F. (2005). Toxicological aspects of the South American herbs cat's claw (Uncaria tomentosa) and Maca (Lepidium meyenii): A critical synopsis. Toxicological Reviews, 24(1), 11-35. PubMed
- Gonzales, G. F. (2012). Ethnobiology and ethnopharmacology of Lepidium meyenii (Maca), a plant from the Peruvian highlands. Evidence-Based Complementary and Alternative Medicine, 2012, 193496. PubMed
- Clément, C., Diaz Grados, D. A., Avula, B., et al. (2010). Influence of colour type and previous cultivation on secondary metabolites in hypocotyls and leaves of maca (Lepidium meyenii Walpers). Journal of the Science of Food and Agriculture, 90(5), 861-869. PubMed
- Gonzales, C., Rubio, J., Gasco, M., et al. (2006). Effect of short-term and long-term treatments with three ecotypes of Lepidium meyenii (MACA) on spermatogenesis in rats. Journal of Ethnopharmacology, 103(3), 448-454. PubMed
These statements have not been evaluated by the Food and Drug Administration. This content is not intended to diagnose, treat, cure, or prevent any disease.
This article is for educational purposes only and is not a substitute for medical advice. Always talk with your healthcare provider before starting maca or any supplement, especially if you are pregnant, breastfeeding, under 18, have a medical condition, or take prescription medicine.
