High Fiber Linked to Fewer Bowel Symptoms in CRC Survivors

Eating more fiber may help reduce bowel symptoms, such as diarrhea, among colorectal cancer (CRC) survivors, according to a large Dutch cohort study.1

This prospective cohort study is published in JAMA Network Open.

Higher dietary fiber intake was associated with a reduced risk of moderate to severe diarrhea up to 2 years after diagnosis. | Image credit: monticellllo - stock.adobe.com

“We described the prevalence of bowel-related symptoms up to 5 years after diagnosis in CRC survivors participating in a large prospective cohort study,” wrote the researchers of the study. “Almost half of the survivors (46.7%) reported bowel-related symptoms at 6 months, whereas more than one-third (35.7%) still experienced bowel-related symptoms at 5 years after diagnosis.”

CRC survivors experience significantly higher rates of long-term bowel dysfunction compared with non-CRC survivors and individuals without cancer.2 Previously, a study that utilized data from the 2009 US National Health and Nutrition Examination Survey found that CRC survivors reported more frequent leakage of gas, liquid stool, and solid stool and had twice the odds of solid stool incontinence (OR, 2.09, 95% CI 1.24-3.53) compared with other groups. These issues were particularly pronounced in women and adults over age 60.

This study used data from the Colorectal Cancer: Longitudinal, Observational Study on Nutritional and Lifestyle Factors study.1 A total of 1751 adults with stage I to IV CRC were recruited at diagnosis from 11 hospitals across the Netherlands between August 2010 and February 2020. Participants were followed for up to 5 years after diagnosis, with data collected at 6 months, 2 years, and 5 years post-diagnosis. Clinical information, including treatment type and disease characteristics, was obtained from hospital records and national registries. Habitual dietary fiber intake was assessed using validated food frequency questionnaires. Bowel-related symptoms—including diarrhea, constipation, bloating, mucus in stools, frequent stools, and false urgency—were self-reported via questionnaires, and health-related quality of life was measured using the European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire Core 3.

Associations between fiber intake and bowel symptoms were analyzed using multivariable logistic regression, adjusting for relevant clinical and demographic factors.

At 6 months post-diagnosis, 46.7% of individuals reported symptoms, with diarrhea, constipation, bloating, and urgency being most frequent, particularly among those who received chemotherapy (58.3%). At 2 years, 40.6% continued to experience symptoms, and at 5 years, 35.7% still reported them, mainly among survivors treated with radiotherapy (53.8% at 2 years and 51.1% at 5 years).

Diarrhea was the greatest impact on health-related quality of life, showing a decrease of 9.6 points (95% CI, −14.0 to −5.2) at 5 years. Higher dietary fiber intake was linked to a lower risk of moderate-to-severe diarrhea, with each 10-gram/day increase reducing odds at 6 months (OR, 0.44; 95% CI, 0.28-0.70) and 2 years (OR, 0.53; 95% CI, 0.30-0.94), though this association was not statistically significant at 5 years (OR, 0.43; 95% CI, 0.16-1.13).

However, the researchers noted the study had some limitations. As an observational study, residual confounding and reverse causation cannot be fully ruled out because participants with diarrhea might have altered their fiber intake. Symptom assessments were timed from diagnosis rather than treatment completion, and data on symptom management or baseline bowel issues were limited. No non-cancer comparison group was included, and survivors with inflammatory bowel disease were excluded, suggesting reported symptoms are likely related to CRC or its treatment.

Despite these limitations, the researchers believe the study suggests a link between increased dietary fiber intake and reduced risk of bowel symptoms in CRC survivors.

“CRC survivors with bowel-related symptoms may benefit from management of those symptoms as part of their cancer care,” wrote the researchers. “Higher intake of dietary fiber was associated with a lower prevalence of diarrhea, which implies the potential role of nutritional counseling in management of bowel-related symptoms. Our findings provide an evidence base for investigating nutritional strategies, including increasing dietary fiber intake, to target bowel-related symptoms in CRC survivors.”

References

1. Klaassen-Dekker N, Witteman BJM, Heek TV, et al. Bowel-related symptoms and dietary fiber intake in colorectal cancer survivors. JAMA Netw Open. 2025;8(11):e2542147. doi:10.1001/jamanetworkopen.2025.42147

2. Sall K, Cheung WY. Prevalence of bowel dysfunction in colorectal cancer survivors. J Clin Oncol. 2012;30(4_suppl):638. doi:10.1200/jco.2012.30.4_suppl.638