Exploring the impact of dietary theobromine on endometriosis risk: Evidence from Mendelian randomization and NHANES data

Endometriosis is a chronic inflammatory estrogen-dependent inflammatory disorder. Theobromine has been implicated in diverse health benefits, including anti-inflammatory and vasodilatory properties. However, the precise association between theobromine and endometriosis remains largely undetermined. To address this gap, this study sought to explore the causal relationship between theobromine exposure and the risk of endometriosis by leveraging Mendelian randomization (MR) and data from the National Health and Nutrition Examination Survey (NHANES). This study included 244 participants from the NHANES (1999-2004). Multivariable logistic regression (adjusted for age, body mass index, smoking, alcohol intake, and energy intake) assessed associations between dietary theobromine intake and endometriosis diagnosis age. Two-sample MR (16,588 cases/1,11,583 controls) used 12 theobromine-associated single-nucleotide polymorphisms (P < 5 × 10⁻⁸) as instruments, with inverse variance weighted analysis. MR assumptions were verified via F-statistics (>10), heterogeneity (Cochran's Q P > .05), and pleiotropy (MR-Egger P > .05). In the observational study (NHANES), each 1 μg/d increment in dietary theobromine intake was associated with a 1.49-year delay in endometriosis diagnosis age (β = 1.49, 95% CI: 0.02-2.95, P = .048) after multivariable adjustment. In the MR analysis, the inverse variance weighted method showed a significant causal effect estimate of β = -0.1057 (95% CI: -0.2098 to -0.0016, P = .045) for the effect of theobromine on endometriosis risk. Sensitivity analyses confirmed robustness against pleiotropy and heterogeneity. This study suggests a potential causal relationship between dietary theobromine intake and a modestly reduced risk of endometriosis, providing preliminary insights into the potential protective effects of theobromine against the development of this condition. However, further investigations are necessary to validate these findings and to understand the underlying biological mechanisms.