The Association of Dietary Fiber and Cancer Development in Rural Post-menopausal Women of Nebraska

Abstract Objectives Determine the extent to which diets with higher fiber intakes (g) at baseline are independently associated with cancer development by final study visit in a cohort of rural post-menopausal women. Methods This study was a secondary analysis of participants in a four-year randomized controlled trial evaluating the effect of vitamin D and calcium supplementation (2000 IU/d vitamin D3 and 1500 mg/d calcium) on cancer development in rural post-menopausal women in Nebraska (June 2009-August 2015). Diets, including fiber intake (total, soluble, fruit-vegetable, grain and bean fiber), were evaluated via a 2005 Block Food Frequency Questionnaire at baseline. T-tests were used to evaluate the difference in dietary fiber intakes between all-type cancer and non-cancer groups. Logistic regression models, controlling for pertinent covariates, were used to determine if dietary fiber intake at baseline is associated with the cancer development. Dietary fiber variables were log-transformed and stratified by treatment group. Results There were 1977 participants available for analysis. Median total fiber intake was 14.35 g or 65% of the Dietary Reference Intake. There was no significant difference between dietary fiber intakes at baseline between the cancer group and non-cancer group. For people on vitamin D and calcium supplementation, higher dietary soluble fiber and fruit-vegetable fiber intakes at baseline were protective against cancer development [Soluble OR: 0.50; 95% CI (0.26, 0.96); Fruit-vegetable OR: 0.56; 95% CI (0.33, 0.94)]. In participants without vitamin D and calcium supplementation, the odds of having higher bean fiber intake was 1.62 times higher in those with cancer [OR: 1.62 (95% CI (1.07, 2.47)]. Total fiber and grain fiber intakes were not significantly associated with cancer development. Conclusions While low fiber intake is prevalent among rural post-menopausal women, those with higher intakes of soluble and fruit-vegetable fiber may be more protected against development of all-type cancer when supplemented with calcium and vitamin D. Further analysis should examine the relationship between supplementation and bean fiber intake on the development of cancer. Funding Sources The original study was funded by the National Cancer Institute and Creighton University internal funding. No additional funding was used for the secondary analysis.