Physiological utilization of dietary protein:: Interactions between meal frequency and protein source

Metabolism plays an essential role in the physiological utilization of nutrients. Discontinuous feeding forces the body to store nutrients in order to cover demands during post-absorptive periods. Metabolic constraints for the storage and mobilization of nutrients are supposed to have adverse effects on the efficiency of their utilization for physiological purposes. For this reason, we discussed previously the metabolic utilization of dietary protein to depend on dietary habits. As an example, we showed that an equal daily amount of protein fed in six instead of two meals resulted in an improved protein status. This chapter describes the interactions of meal frequency (two versus six meals a day) and the protein source of the diet (casein versus soya), in relation to body weight development and immune response of protein-restricted rats. Individually housed male Wistar rats (WU/Harlan, 8 weeks) randomly divided into four nutritional groups (n = 10), received a protein-restricted diet containing 1 g of protein (casein or soya) and 218 kJ ME day(-1) in either two or six meals day(-1). After 6 weeks of experimental feeding, protein status was characterized by post-absorptive (CO2)-C-14 breath test measurements, followed by an immunization procedure with thyroglobulin and determination of blood plasma antibody titres. The lour nutritional groups were ranked for the various physiological parameters. Overall ranking tended to give best results for the casein rats. There was, however, an interaction with the meal frequency. Rats fed two meals had the better score in the casein group but a lower score in the soya group when compared with rats fed the same protein diet by six meals. The results indicate that dietary habits can modulate physiological utilization of dietary protein.