May calcium absorption effectiveness of prebiotics be affected by the nutritional status of vitamin D?

Abstract

Low Ca intake (CaI) is related to osteoporosis among others pathologies. Ca absorption (Abs) is regulated by vitamin D which, within limits, compensate for the lesser CaI. Prebiotics also positively affect Ca Abs by selectively increasing acid lactic bacteria?s which releases metabiotic products. Short-chain fatty acids improve Ca salts solubility by lowering intestinal pH, and favor colonic epithelial cell proliferation. We wonder if the prebiotic effectiveness to absorb Ca may be affected by vitamin D (VD) insufficiency. The effectiveness of Galactooligosaccharides/Fructooligosaccharides (GOS/FOS®) mixture to increase CaAbs was evaluated in a model of vitamin D (VD) insufficiency and established osteopenia. Wistar rats were ovariectomized and fed a commercial diet during 15 days postsurgery. Then, rats were divided: 32 fed a diet VD-free (0 IU%) during 45 days to become VD insufficient (-D) and 16 fed a normal VD diet (100 IU%) (+D). At day-60, +D were subdivided in 2 and -D in 4 groups and received during 45 days: AIN´93 (control diet) (+D0.5%); AIN´93 containing 0.3%Ca and 2.5%GOS/FOS® (9:1) (+D0.3%P); VD free-AIN´93 (-D0.5%); VD free-AIN´93 containing 0.3%Ca (-D0.3%); last diet containing 2.5% (-D0.3%P) or 5% GOS/FOS (-D0.3%:2xP). Food intake and faeces (F) were collected to determine CaI and CaF. Ca Abs% = CaI ? CaF/ CaI x 100. Ca Abs % as mean±SD: -D0.5%: 32.71±1.74; -D0.3%: 38.33±2.33; -D0.3%P: 44.71±1.84; -D0.3%x2P: 56.40±1.39; +D0.3%P: 87.45±1.82; +D0.5%: 67.80±2.21. As expected, VD insufficiency reduced Ca Abs% (-D0.5% and ?D0.3% vs. +D0.5%; p<0.001). Moreover, GOS/FOS® effectiveness was negatively affected (-D0.3%P vs. +D0.3%P; p<0.001). Ca Abs% of free-VD diets containing GOS/FOS® mixture was improved by increasing prebiotic % in the diet (-D0.3%P vs. -D0.3:2xP; p<0.01).