Dietary Fiber, Genetic Variations of Gut Microbiota-derived Short-chain Fatty Acids, and Bone Health in UK Biobank

Context: Dietary fiber intake may relate to bone health. Objective: To investigate whether dietary fiber intake is associated with bone mineral density (BMD), and the modification effect of genetic variations related to gut microbiota-derived short-chain fatty acids (SCFAs). Design: The associations of dietary fiber intake with estimated BMD derived from heel ultrasound and fractures were assessed in 224 630 and 384 134 participants from the UK Biobank. Setting: UK Biobank. Main Outcome Measures: Estimated BMD derived from heel ultrasound Results: Higher dietary fiber intake (per standard deviation) was significantly associated with higher heel-BMD (beta [standard error] = 0.0047 [0.0003], P = 1.10 x 10(-54)). Similarly significant associations were observed for all the fiber subtypes including cereal, fruit (dried and raw), and vegetable (cooked and raw) (all P<.05). A positive association was found in both women and men but more marked among men except for dietary fiber in cooked vegetables (all P-interaction<.05). A protective association was found between dietary fiber intake and hip fracture (hazard ratio, 95% confidence interval: 0.94, 0.89-0.99; P = 3.0 x 10(-2)). In addition, the association between dietary fiber and heel BMD was modified by genetically determined SCFA propionate production (P-interaction = 5.1 x 10(-3)). The protective association between dietary fiber and heel BMD was more pronounced among participants with lower genetically determined propionate production. Conclusions: Our results indicate that greater intakes of total dietary fiber and subtypes from various food sources are associated with higher heel-BMD. Participants with lower genetically determined propionate production may benefit more from taking more dietary fiber.