Fiber Intake Associated With Lower Mortality in Patients with Colorectal Cancer

Higher fiber intake after the diagnosis of non-metastatic colorectal cancer (CRC) is associated with lower CRC-specific and overall mortality, according to a study published in JAMA Oncology.

Colorectal cancer is the third most common cancer and third-leading cause of cancer death in the United States. While high dietary fiber intake previousl has been associated with a lower risk of CRC, there is no known benefit of fiber intake on CRC survivors.

“Due to lack of data on post-diagnostic diet and CRC survival, most dietary recommendations for CRC survivors are primarily based on incidence studies,” wrote the authors. “Therefore, identifying prognostic dietary factors is needed to improve CRC survivorship.”

Authors of the study analyzed 1575 healthcare professionals with stage I to III CRC from the Nurses’ Health Study (NHS) and Health Professionals Follow-up Study (HPFS). Participants were mailed a questionnaire focusing on medical history and lifestyle factors at baseline and every 2 years after.

Dietary data were collected and updated every 4 years using Food Frequency Questionnaires (FFQs). The baseline for NHS was 1980 and the baseline for HPFS was 1986. The study was conducted between December 23, 2016, and August 23, 2017.

Dietary fiber intake data collected by the FFQs inquired about how often, on average, the participant consumed each food of a specific serving size in the prior year. Authors calculated the daily intake for each nutrient by multiplying the reported frequency of consumption by its nutrient content and then summing across all foods.

Authors determined colorectal cancer-specific and overall mortality after adjusting for other potential predictors for cancer survival.

Results showed that high fiber intake associated with lower mortality. The multi-variable hazard ratio per each 5 g increase in intake per day was .78 for CRC-specific mortality and .86 for all-cause mortality. The benefit of increasing fiber intake capped at approximately 24 g/d. Patients who increased their fiber intake after diagnosis had a lower mortality rate, with each 5-g/d increase in intake was linked to an 18% lower CRC-specific mortality and 14% lower all-cause mortality.

There was no substantial association between fiber intake and tumor subsite or stage.

When looking at specific sources of fiber, cereal fiber was associated with lower CRC-specific mortality and all-cause mortality; vegetable fiber was associated with lower all-cause mortality but not CRC-specific mortality; and no association was found for fruit fiber.

Whole grain intake was also associated with lower CRC-specific mortality.

“Our present study adds to the existing literature and suggests that the effect of high fiber intake may extend beyond protection against cancer incidence and contribute to better prognosis after cancer is established,” concluded the authors.