Calcium effects on bodyweight appear to be mediated in part by changes in gut microflora and altered by dietary matrix

Abstract

Calcium (Ca) intake variably affects bodyweight (BW) regulation. Delivery matrix may affect Ca effects. Gut microflora is now a considered variable in BW regulation. Three isonitrogenous, isocaloric, 45 kcal% fat diets were fed to male C57/BL6J mice (n=10/group) in two diet‐induced obesity tests. Isolated soy protein was used for diets containing adequate (0.5 wt%, D1) or high (1.5 wt%, D2) amounts of Ca as CaCO3, while non‐fat dry milk was used in a second 1.5 wt% Ca diet (NFDM), providing 0.5 wt% Ca as intrinsic dairy Ca. Test 1: 5 wk old mice were fed test diets for 12 wks. Mice fed D1 and NFDM consumed similar amounts of feed, but NFDM fed mice gained less BW and body fat (p<0.05). Mice fed D2 consumed the most feed, gained the most BW and body fat (p <0.05). Gut microflora community structure was determined by 16SrRNA pyrosequencing of feces collected during the last 48 hrs of study. UniFrac analysis and PCA clustering of mice with similar microflora clearly separated D1, D2, and NFDM at the genera level. Test 2: Test 1 protocol, except that mice were pre‐fed D1 for 12wks prior to being fed D1, D2, or NFDM for an additional 8wk period. Similar responses in feed intake, BW, body fat and microflora shifts were seen. Dairy was most effective in obesity prevention (Test 1) and its effects were correlated to changes in gut microflora. 1.5 wt% CaCO3 increased obesogenic tendencies. Funded by the Dairy Research Institute.