Vitamin D Status, Fiber Intake, and Type 2 Diabetes in U.S. Adults

Vitamin D and fiber intake are nutritional factors that could affect the development of type 2 diabetes (T2D), potentially by reducing insulin resistance. Therefore, we hypothesized that the influence of vitamin D on T2D might depend on fiber intake. This study investigated the association between vitamin D status and T2D according to fiber intake. The present study analyzed data from 9,656 American adults (≥20 years old) who participated in the National Health and Nutrition Examination Survey (NHANES) 2007-2010. The serum concentration of 25-hydroxyvitamin D [25(OH)D] was used as a biomarker for vitamin D status. The T2D classification was based on two criteria: T2D^a was identified using only self-reported questionnaire data and T2D^b was identified based on both survey and laboratory data. The deficient vitamin D status (<50 nmol/L) was used as the reference group. After controlling for sociodemographic, behavioral, and dietary factors, the odds ratios (ORs) were 0.72 (95% confidence interval [CI]: 0.58, 0.90) for T2D^a and 0.60 (0.50, 0.80) for T2D^b in the sufficient vitamin D status (≥75 nmol/L). Furthermore, the total vitamin D concentration exhibited dose-dependent associations with lower OR values for T2D^a (P for trend = .005) and T2D^b (P for trend <.001). Among participants with high-fiber intake, the OR values for T2D^b were 0.60 (95% CI: 0.42, 0.90) at suboptimal vitamin D status and 0.49 (95% CI: 0.31, 0.77) at sufficient vitamin D status. Moreover, the significant dose-dependent association persisted in the high-fiber-intake subgroup (P for trend = .004). Therefore, combining vitamin D plus high-fiber intake would help reduce the prevalence of diabetes, although the interaction analysis results were not statistically significant.