In vivo and in vitro digestibility of the calcium contained in foods of animal and plant origin

The aim of this study was to assess Ca digestibility using in vitro and in vivo methodology (rats). The tested foods were: cheese (Grana Padano; Emmentaler), soybean-based products (tofu; burger; milk; yogurt), and legumes (peas; beans). Ca digestibility was found to be high in Emmentaler (84.3%), Grana Padano (83.6%) and tofu (80.3%), with significantly lower values for soya burgers (64.1%) and soya milk (60.6%). The lowest values were detected in peas (49.6%) and beans (31.4%). Poor correlation was found between in vivo and in vitro data. The current RDAs have been established on the basis of 30% Ca digestibility, a value which reduces the risk of calcium deficiency but underestimates the contribution of dairy products. The adoption of specific, instead of general, digestibility values for each food might improve the accuracy of dietary formulations. This will require considerable efforts to develop simple and reliable in vitro methods to assess foods.