Introduction: Epidemiological evidence regarding the association between equol and precancerous colorectal lesions, including adenomas, sessile serrated lesions, and traditional serrated adenomas, remains unclear. Moreover, since equol production status depends on the composition of the gut microbiota and varies widely among individuals, evaluation based on plasma levels is essential. In this study, we evaluated the association between plasma equol levels and precancerous colorectal lesions. Methods: This cross-sectional study included residents aged 40-79 years in Izu Oshima, Japan. Blood samples were collected at study registration prior to colonoscopy under fasting conditions. In 2024, plasma equol levels were analyzed by gas chromatography-mass spectrometry, and individuals above the measurement quantification limit were classified as equol producers. Colonoscopy was performed for screening, and lesions were assessed based on endoscopic and pathological findings. Odds ratios (ORs) and their 95% confidence intervals (CIs) for precancerous lesions were calculated. Results: Of the 993 participants analyzed, 509 had precancerous colorectal lesions, while 484 served as controls. No significant association was observed between equol production status and the presence of precancerous colorectal lesions (OR: 1.04, 95% CI: 0.77-1.40). Although not statistically significant, an inverse trend was suggested in advanced lesions, defined as advanced adenomas or SSLs with dysplasia (OR: 0.63, 95% CI: 0.34-1.18). Conclusion: This study did not provide significant evidence of an association between equol production status and the presence of precancerous colorectal lesions. Future prospective cohort studies and detailed analysis of intestinal microbiota are needed to clarify the effects of equol on colorectal carcinogenesis.
Kaneta et al. (Mon,) studied this question.