Calcium bioavailability from dairy products and its release from food by in vitro digestion

Abstract

Food products are an exclusive source of nutrients necessary for the development and proper functioning of human organism. The key issue in nutrition is the bioavailability of nutrients rather than the supply of their adequate amounts in a diet. Calcium is the basic structural element of bones and teeth. It is also an element with a wide range of physiological functions, e.g. it is responsible for the right excitability of muscular and nervous system, normal heart function, hormonal secretion, blood clotting, cell membrane permeability and activation of various enzymes. It is universally acknowledged that the main source of calcium for a human organism is milk and dairy products, owing to their rich content and high availability of calcium. However, certain stages in food processing technologies may depress the high bioavailability of dietary nutrients. In this paper, long-term research findings about the bioavailability of calcium in milk products have been summarized, in addition to the information about calcium uptake from bread or other popular breakfast meals composed of milk products in combination with cereal component. The popular opinion that milk and other dairy products are the best and most valuable source of highly available calcium has indeed been supported. However, an in vitro study demonstrates that an addition of cereal to milk or yoghurt significantly diminishes the quantity of calcium released during digestion, which could contribute to the development of calcium insufficiency or augmentation of its symptoms.