Prebiotics and calcium bioavailability.

A prebiotic substance has been defined as a non-digestible food ingredient that beneficially affects the host by selectively stimulating the growth and/or activity of one or a limited number of bacteria in the colon. Therefore, compared to probiotics, which introduce exogenous bacteria into the colonic microflora, a prebiotic aims at stimulating the growth of one or a limited number of the potentially health-promoting indigenous micro-organisms, thus modulating the composition of the natural ecosystem. In recent years, increasing attention has been focussed on the possible beneficial effects of prebiotics, such as enhanced resistance to invading pathogens, improved bowel function, anti-colon cancer properties, lipid lowering action, improved calcium bioavailability, amongst others. The objective of this review is to critically assess the available data on the effects of prebiotics on calcium bioavailability, and place it in the context of human physiology and, when possible, explain the underlying cellular and molecular mechanisms. The review will also try to highlight future areas of research that may help in the evaluation of prebiotics as potential ingredients for functional foods aimed at enhancing calcium bioavailability and protecting against osteoporosis.