Does dietary broccoli fibre influence body composition of the healthy rat in the presence of high and low fat?

Background: Daily intake of dietary fibre is important in preventing gut-related disorders, cardiovascular diseases, type 2 diabetes, cancer and obesity. Fermentable carbohydrates such as pectin, gums, resistant starch, and non-starch polysaccharides can enhance the metabolic absorption of minerals, including calcium, magnesium and iron from the gut. Objective: To determine if feeding broccoli fibre in high and low fat diets alters body composition and bone density in the healthy rat. Design: Sixty-four male Sprague Dawley rats (9 weeks of age) were fed four experimental dietary treatments (16 rats per treatment) for 17 weeks. The dietary treatments were: 1) low corn oil and cellulose, 2) low corn oil and broccoli fibre, 3) high corn oil and cellulose, and 4) high corn oil and broccoli fibre. Body composition and bone density were assessed by DEXA scan analysis. Serum levels of C-terminal telopeptides of type 1 collagen (CTX), a resorption marker, were also measured. Outcomes: Body fat mass (p=0.002) and fat percentage (p<0.001) were significantly higher in rats fed the high fat diets. Lean mass, lumbar spine (area, bone mineral content and density), and femur measurements (bone mineral content and density) were higher in rats fed the low fat diets. Broccoli fibre supplementation increased lumbar spine area (p=0.040), lumbar spine bone mineral content (p=0.077), femur area (p=0.079), and femur bone mineral content (p=0.074). Conclusion: Low fat diets increased lean mass and bone area, mineral content and density in the lumbar spine and femur. Broccoli fibre supplementation had only a small impact on bone health through increased lumbar spine bone area.