An antioxidant called L-ergothioneine, found in certain mushrooms, reduced period pain in a small study of 40 women. Participants took a daily 120-milligram supplement over three menstrual cycles, reporting lower pain scores compared to a placebo group. The findings suggest it targets oxidative stress in uterine cells.
Researchers led by Guohua Xiao at Gene III Biotechnology Co. in Nanjing, China, tested L-ergothioneine on women aged 18 to 30 with primary dysmenorrhea, a common cause of menstrual pain not linked to conditions like endometriosis. None had used painkillers or other treatments in the prior month. Half received 120 milligrams of the supplement daily for three cycles; the rest got a placebo. Initial pain scores averaged 4.8 out of 10, dropping to 4.1, 3.6 and 2.3 for the supplement group, with no notable change in the placebo group, according to a preprint on medRxiv (DOI: 10.64898/2026.03.26.26349375). No side effects were reported in either group. Xiao explained that L-ergothioneine accumulates in cells over time, potentially neutralizing free radicals in uterine tissue before inflammation escalates. “Instead of treating the symptom acutely when the pain is already severe, EGT acts as a nutritional foundational support, potentially reducing the reliance on strong medications,” Xiao said. The study found no difference in systemic inflammation levels between groups, supporting a localized antioxidant effect, Xiao added. Andrea Maier at the University of Melbourne called the mechanism biologically plausible but urged a larger trial for confirmation. Xiao's team plans a multi-center study to assess safety and efficacy further. Long-term painkiller use like ibuprofen carries risks including heart issues and kidney problems, unlike this supplement, which the kidneys excrete once saturated.
