Dietary Phytoestrogen Intake and The Risk of Endometriosis in Iranian Women: A Case-Control Study

Background: Endometriosis is an important gynecologic disease affecting reproductive-age women. Based on the effect of phytoestrogens on inflammatory, immunological and hormonal factors, limited studies have suggested that phytoestrogen consumption could probably modulate endometriosis risk. The aim of this study was to evaluate the relationship between phytoestrogen intake and endometriosis risk.

Materials and methods: In the present case-control study, 78 women with a laparoscopically confirmed endometriosis and 78 normal pelvis women (as the control group), were recruited. Common dietary intake was recorded by a validated 147-item semi-quantitative food frequency questionnaire (FFQ). Type of phytoestrogen in each dietary item was analyzed by the database from the United States Department of Agriculture (USDA). A logistic regression model was used to determine the association between phytoestrogen intake and endometriosis risk.

Results: Higher intake of total phytoestrogen (P-trend=0.01), total isoflavones (P-trend=0.002) specially formononetin (P-trend=0.04) and glycitein (P-trend=0.04), total lignan (P-trend=0.01) specially secoisolariciresinol (P-trend=0.01) and lariciresinol (P-trend=0.02) and matairesinol (P-trend=0.003), and total coumestrol [third quartile odds ratios (OR): 0.38; 95% confidence intervals (CI): 0.15-0.96; P-trend=0.1] was related to reduced endometriosis risk. Among food groups, only isoflavin (OR: 0.48; 95% CI: 0.44-0.63), lignan (OR: 0.66; 95% CI: 0.62-0.94), coumestrol (OR: 0.64; 95% CI: 0.51-0.99), phytoestrogen (OR: 0.46; 95% CI: 0.38-0.83) in dairy products and coumestrol in fruits (OR: 0.69; 95% CI: 0.03-0.77) were negatively associated with endometriosis risk.

Conclusion: Phytoestrogens have a major impact on the level of hormones, and immune and inflammatory markers; thus, it can play an important role in the control and prevention of many diseases. Due to the inflammatory nature of endometriosis and the effect of hormones on the progression of the disease, the role of phytoestrogens consumption in the progression and regression of the disease should be assessed in future works.