Study Overview
Objective. To evaluate the association between intake of dietary fiber and type 2 diabetes.
Design. Case-cohort study (EPIC-InterAct Study), which is nested within the large prospective cohort study EPIC (European Prospective Investigation into Cancer & Nutrition) [1]. EPIC includes participants from 10 European countries and was designed to investigate the relationships between diet, nutritional status, lifestyle, and environmental factors and the incidence of cancer and other chronic disease [1].
Setting and participants. The EPIC-Interact study used data from 8 European countries (Denmark, France, Germany, Italy, the Netherlands, Spain, Sweden, and UK). The Interact sample includes 12,403 individuals who were identified as having developed type 2 diabetes, and a random subcohort of controls who were free of diabetes at baseline (n = 16,835, including 778 cases of incident diabetes) selected from 340,234 eligible EPIC participants. Of the 28,460 participants in the EPIC-InterAct study, excluded were those with prevalent diabetes, missing diabetes status information, post-censoring diabetes, extreme energy intake (top and bottom 1%), and missing values for education level, physical activity, smoking status, and BMI, leaving a final sample of 11,559 cases and 15,258 subcohort participants. No differences were observed in baseline characteristics between the included and excluded participants.
Analysis. Country-specific hazard ratios (HRs) were estimated using Prentice-weighted Cox proportional hazards models and were pooled using a random effects meta-analysis. Dietary intake over the previous 12 months before recruitment was assessed by country-specific or center-specific assessment methods (food-frequency questionnaire and dietary histories) that were developed and validated locally, and data were converted to nutrient intake.
Main outcome measure. Incident cases of diabetes.
Main results. During a median of 10.8 years of follow-up, total fiber intake was associated with a lower risk of diabetes after adjusting for lifestyle and dietary factors (hazard ratio for the highest quartile of fiber intake [> 26 g/day] vs the lowest [< 19 g/day], 0.82; 95% confidence interval, 0.69–0.97, P for trend = 0.02). When the researchers focused on specific types of fiber, they found that people who consumed the highest amounts of cereal and vegetable fiber were 19% and 16%, respectively, less likely to develop type 2 diabetes compared with those who consumed the lowest amounts (P < 0.001). Intake of fruit fiber was not associated with risk of diabetes. When the analyses were additionally adjusted for BMI, the inverse associations between intake of fiber and diabetes were attenuated and no longer statistically significant.
The researchers also conducted a meta-analysis that included 18 other cohorts in addition to the current EPIC-InterAct study. The summary relative risks per 10/g day increase in intake were 0.91 (95% CI, 0.87–0.96) for total fiber, 0.75 (95% CI, 0.65–0.86) for cereal fiber, 0.95 (95% CI, 0.87–1.03) for fruit fiber, and 0.93 (95% CI 0.82–1.05) for vegetable fiber.
Conclusion. Individuals with diets rich in fiber, in particular cereal fiber, may be at lower risk of type 2 diabetes.