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High fiber intake after colorectal cancer diagnosis improves survival
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High fiber and whole grain intake after nonmetastatic colorectal cancer diagnosis was associated with lower colorectal cancer-specific and overall mortality, according to published findings.
“To our knowledge, this is the first prospective study examining the prognostic influence of fiber intake among patients with colorectal cancer,” Andrew T. Chan, MD, MPH, associate professor in the division of gastroenterology at Massachusetts General Hospital and Harvard Medical School, and colleagues wrote. “Our findings provide novel evidence for the potential benefit of increasing fiber and whole grain consumption among patients with colorectal cancer.”
Earlier research showed fiber lowered risk for colorectal cancer by minimizing exposure to carcinogens through dilution of fecal content. Fiber also offers systemic benefits for insulin sensitivity and metabolic regulation, which are known to be associated with colorectal cancer prognosis.
However, whether an association exists between fiber intake and survival among patients with colorectal cancer remained largely unknown.
Chan and colleagues evaluated rates of colorectal cancer-specific and overall mortality among 1,575 patients (women, n = 963; mean age, 68.6 years) with stage I to stage III colorectal cancer between December 2016 and August 2017.
Researchers used a validated food frequency questionnaire to measure consumption of total fiber, other fiber sources and whole grains between 6 months and 4 years after colorectal cancer diagnosis.
Over a median follow-up of 8 years, 773 individuals died, including 174 (22.5%) related to colorectal cancer.
Fiber intake appeared inversely associated with colorectal cancer-specific mortality after adjusting for other variables associated with cancer prognosis. The multivariable HR per 5-g increase in fiber intake per day was 0.78 (95% CI, 0.65-0.93) for colorectal cancer-specific mortality and 0.85 (95% CI,0.79-0.93) for all-cause mortality.
Sensitivity analysis — which excluded the first year of follow-up to avoid bias associated with occult recurrence or undiagnosed major illness — showed similar results for each 5-g daily increment of fiber for colorectal cancer-specific mortality (HR = 0.8; 95% CI, 0.66-0.97) and all-cause mortality (HR = 0.85; 95% CI, 0.78-0.93).
Researchers also evaluated whether changing fiber intake after diagnosis impacted survival and found patients who increased fiber intake had a lower mortality rate. Per each 5-g daily increase in fiber intake, researchers observed an 18% (95% CI, 7-28) lower colorectal cancer-specific mortality and 14% (95% CI, 8-19) lower all-cause mortality.
Researchers also measured associations by dietary sources of fiber — cereals, vegetables and fruits. Fibers from cereals showed an inverse correlation with mortality after adjusting for fruit and vegetable fiber (colorectal cancer-specific mortality, HR per 5-g increment= 0.67 (95% CI, 0.5-0.9; all-cause mortality, HR per 5-g increment = 0.78; 95% CI, 0.68-0.9). Vegetable fiber reduced risk for all-cause mortality (HR per 5-g increment = 0.83; 95% CI, 0.72-0.96), but not colorectal-cancer specific mortality. Researchers observed no association with fruit fiber.
Whole grain consumption also lowered colorectal cancer-specific mortality (HR per 20-g daily increment = 0.72; 95% CI, 0.59-0.88), which weakened after adjusting for fiber intake (HR = 0.77; 95% CI, 0.62-0.96).
Despite multiple limitations, including self-reported fiber intake without adjusting for measurement error and unavailable treatment data, a higher fiber intake after colorectal cancer diagnosis appears linked to decreased risk for mortality among patients with colorectal cancer.
“Our findings provide support for the nutritional recommendations of maintaining sufficient fiber intake among colorectal cancer survivors,” the researchers wrote. – by Melinda Stevens
Disclosures: Chan reports previous consultant roles with Aralez Pharmaceuticals, Bayer and Pfizer Inc. for work unrelated to the study. The other authors report no relevant financial disclosures.
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