Efficacy and Safety of Maca (Lepidium meyenii) in Patients with Symptoms of Late-Onset Hypogonadism: A Randomized, Double-Blind, Placebo-Controlled Clinical Trial.

The short version

This randomized, double-blind, placebo-controlled trial with 80 men explored whether Maca (Lepidium meyenii), a root vegetable traditionally grown high in the Peruvian Andes and eaten as a nutritional "superfood," can ease late-onset hypogonadism (LOH), the cluster of low-testosterone-type symptoms, such as fatigue, low mood, reduced libido, and erectile difficulty, that many men develop with age even when their blood testosterone level is technically normal. Because standard testosterone replacement therapy carries cardiovascular and prostate-cancer risks, researchers wanted to know whether Maca, long used as a folk aphrodisiac and fertility aid, could offer relief without those risks. Eighty men over 40, recruited as outpatients at two South Korean hospitals and randomly split into two groups, took either 1,000 mg Maca tablets or an identical-looking placebo, two tablets three times a day before meals (about 5 grams of Maca daily), for 12 weeks. Neither the men nor the study staff knew who was getting the real supplement. Researchers tracked symptoms with four standard questionnaires covering overall aging-male symptoms, androgen deficiency, erectile function, and urinary symptoms, and ran blood tests for testosterone, cholesterol, and other safety markers at baseline, 4 weeks, and 12 weeks. Only the Maca group showed real improvement: overall symptom scores dropped by nearly 11 points from baseline (p<0.0001), while placebo barely moved (statistically unchanged, p=0.5007), and the difference between groups was highly significant (p<0.0001). Androgen-deficiency screening flipped from mostly positive to mostly negative in the Maca group (70.7% down to 56.1% at 12 weeks, p<0.0001 versus placebo). Erectile function scores rose by 14 points with Maca (p<0.0001, meaning a clear improvement) while the placebo group's scores actually fell, and urinary symptom scores improved with Maca too (p=0.0025) with no such change on placebo. Notably, none of this tracked with testosterone levels, which barely budged in either group, suggesting Maca works through some other pathway the study did not pin down. Only two participants reported mild stomach upset, and no serious safety issues turned up in blood work or vital signs. In men who were not candidates for testosterone therapy, this study found Maca well tolerated, with its effects on sexual and urinary symptoms rather than on lab-measured testosterone itself. The trial ran only 12 weeks, so it cannot say whether benefits last, and every participant was Korean, so results may not generalize to other populations. The researchers themselves flag that the biological mechanism behind Maca's effect is still unknown and call for longer, more mechanistic follow-up studies.

Key findings

• In a 12-week randomized trial, men taking a Maca (a Peruvian root supplement) tablet three times a day scored significantly better on a standard aging-symptoms questionnaire (AMS) than men taking a placebo, improving nearly 11 points from their starting score (p<0.0001).
• Erectile function, measured by the International Index of Erectile Function (IIEF), improved by 14 points in the Maca group while it worsened slightly in the placebo group, a statistically significant difference (p<0.0001).
• Urinary symptoms, tracked with the International Prostate Symptom Score (IPSS), also improved significantly with Maca but not with placebo (p=0.0025), a finding the study authors say has not been clearly shown for Maca before.
• These improvements happened without any significant change in blood testosterone levels, suggesting Maca may work through a mechanism other than raising testosterone.
• Only two participants experienced mild gastrointestinal side effects, and no serious safety problems appeared in blood work or vital signs over the 12-week trial.

Common questions