Longitudinal associations of fiber, vegetable, and fruit intake with quality of life and fatigue in colorectal cancer survivors up to 24 months post-treatment.

Background The increasing colorectal cancer (CRC) survivor population highlights the need for dietary recommendations in order to enhance health-related quality of life (HRQoL) and alleviate symptoms of fatigue, chemotherapy-induced peripheral neuropathy (CIPN) and gastro-intestinal problems. Objectives Because of the therapeutic potential of dietary fiber on the gut, we aim to assess longitudinal associations of post-diagnostic dietary fiber, fruit and vegetable intake, a major source of dietary fiber, with HRQoL, fatigue, CIPN and gastro-intestinal symptoms in CRC survivors from 6 weeks to 24 months post-treatment. Methods In a prospective cohort among stage I-III CRC survivors (n = 459), five repeated study measurements between diagnosis and 24 months post-treatment were executed. Dietary fiber and fruit and vegetable intake were measured by 7-day dietary records. HRQoL, fatigue, CIPN and gastro-intestinal symptoms were measured by validated questionnaires. We applied confounder-adjusted linear mixed-models to analyze longitudinal associations from 6 weeks until 24 months post-treatment, and used hybrid models to disentangle the overall association into intra-individual changes and inter-individual differences over time. Results Higher dietary fiber intake, fruit and vegetable intake were longitudinally associated with statistically significant better physical functioning and less fatigue. Intra-individual analyses showed that an increase of 10 g/d in dietary fiber within individuals over time was associated with better physical functioning (β: 2.3; 95% CI: 0.1, 4.4), role functioning (ability to perform daily activities - 5.9; 1.5, 10.3), and less fatigue (-4.1; -7.7,-0.5). An average increase in fruit and vegetable intake of 100 g/d between individuals over time was predominantly associated with less fatigue (-2.2; -4.2,-0.3). No associations were found with CIPN and gastro-intestinal symptoms. Conclusion Our results suggest that increasing dietary fiber, fruit and vegetable intake is related to better physical and role functioning and less fatigue in the first two years after the end of treatment for CRC.Registration: The EnCoRe study was registered at trialregister.nl as NL6904 (former ID: NTR7099).