Dietary Patterns and Incident Chronic Constipation in Three Prospective Cohorts of Middle- and Older-Aged Adults

Background & Aims: Current literature on diet-constipation associations is limited by small sample sizes and cross-sectional designs. We aimed to comprehensively examine the associations among 5 dietary patterns, their components, and incident constipation. Methods: In 3 large cohorts, the Nurses’ Health Study (NHS), NHSII, and the Health Professional Follow-up Study, we identified chronic constipation based on repeatedly measured self-reported constipation symptoms for ≥12 weeks in the past year. We assessed long-term adherence to 5 dietary patterns (alternate Mediterranean diet [aMED], low-carbohydrate diet, Western diet) and indices (plant-based dietary index [PDI], empirical dietary inflammatory pattern) using validated quadrennial food frequency questionnaires. We used a log-binomial model adjusted for a wide range of confounders, including fiber or ultra-processed food intake, to estimate relative risk (95% confidence interval) for constipation. Results: In the pooled cohort of 27,774 (78.4 ± 5.6 years) NHS, 55,906 (60.5 ± 4.6 years) NHSII, and 12,237 (78.6 ± 5.6 years) Health Professional Follow-up Study participants, we documented 7519 incident constipation cases after 2 to 4 years of follow-up. Compared with the lowest quintiles, the top quintiles of aMED and PDI were associated with 16% (9%–22%) and 20% (14%–27%) reduced risk for constipation, whereas the top quintiles of empirical dietary inflammatory pattern, Western diet, and low-carbohydrate diet were associated with 24% (15%–33%), 22% (11%–33%), and 3% (−3% to 11%) increased risk for constipation, respectively. These associations were independent of total fiber or ultra-processed food intake. Vegetable and nut intake, which is enriched in aMED and PDI, was associated with decreased constipation risks. Conclusion: Our findings suggest that dietary patterns emphasizing plant-based foods and healthy fats may protect against constipation, informing future dietary interventions and treatments for chronic constipation.