Bowel-Related Symptoms and Dietary Fiber Intake in Colorectal Cancer Survivors

Importance: Colorectal cancer (CRC) survivors frequently report bowel-related symptoms, but longitudinal data are scarce and diet has not been extensively investigated in relation to bowel-related symptoms. Objective: To investigate the prevalence of bowel-related symptoms as well as their association with dietary fiber intake until 5 years after CRC diagnosis. Design, Setting, and Participants: This prospective cohort study using data from the Colorectal Cancer: Longitudinal, Observational Study on Nutritional and Lifestyle Factors (COLON) study included CRC survivors with stage I-IV disease recruited at diagnosis from 11 hospitals in the Netherlands between August 2010 and February 2020. CRC survivors were followed up until 5 years after diagnosis. Data were analyzed between April 2024 and March 2025. Exposures: Clinical data including CRC treatment strategy, retrieved from hospital records and national registries, and habitual dietary fiber intake, assessed by a food frequency questionnaire, at 6 months, 2 years, and 5 years after CRC diagnosis. Main Outcomes and Measures: Prevalence of self-reported diarrhea, constipation, flatulence or bloating, frequent stools, mucus in stools, or false urgency at 6 months, 2 years, and 5 years after diagnosis, obtained via a questionnaire. The validated European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire Core 30 (EORTC QLQ-C30) was also used to evaluate prevalence of moderate-to-severe diarrhea or constipation and health-related quality of life (HRQOL) at these time points. Odds ratios (ORs) for associations between fiber intake and bowel-related symptoms (yes or no) were calculated using multivariable logistic regression. Results: Among 1751 CRC survivors who underwent surgery and were included in the analysis, median age at diagnosis was 66 years (IQR, 61-71 years), and 1115 (63.7%) were men. Bowel-related symptoms were reported by 817 of 1751 survivors (46.7%) at 6 months, 614 of 1511 (40.6%) at 2 years, and 290 of 812 (35.7%) at 5 years after diagnosis. At 6 months after diagnosis, symptoms were predominantly reported by survivors who had received chemotherapy (260 of 446 58.3%), whereas symptoms at 2 and 5 years occurred mostly in those who received radiotherapy (86 of 160 53.8% at 2 years and 47 of 92 51.1% at 5 years). Of the studied bowel-related symptoms, diarrhea was associated with the lowest HRQOL score (B, -9.6; 95% CI, -14.0 to -5.2) at 5 years after diagnosis. In multivariable logistic regression analyses, higher fiber intake (per 10-g/d increment) was associated with a significantly lower prevalence of moderate-to-severe diarrhea at 6 months (OR, 0.44; 95% CI, 0.28-0.70) and 2 years (OR, 0.53; 95% CI, 0.30-0.94) after diagnosis, but the association was not statistically significant at 5 years (OR, 0.43; 95% CI, 0.16-1.13). Conclusions and Relevance: In this cohort study of CRC survivors, the prevalence of bowel-related symptoms was considerably high during the 5 years after diagnosis, highlighting a need for effective symptom management. Higher dietary fiber intake was associated with a lower prevalence of diarrhea, suggesting a potential role of diet in management of bowel-related symptoms in CRC survivors.