BACKGROUND: Muscle mass maintenance is largely regulated by basal muscle protein synthesis rates and the capacity to stimulate muscle protein synthesis rates following food intake. The postprandial muscle protein synthetic response is modulated by the amount, source, and type of protein consumed. It has been suggested that plant-based proteins are less potent in stimulating postprandial muscle protein synthesis rates when compared with animal-derived proteins. However, few data support this contention.

OBJECTIVE: To assess postprandial plasma amino acid profiles and the muscle protein synthetic response to the ingestion of wheat protein (hydrolysate) compared to casein and whey protein. DESIGN: Sixty healthy older males (age: 71±1 y, BMI: 25.3±0.3 kg· m-2) received a primed continuous infusion of L-[ring-13C6]-phenylalanine and L-[ring-3, 5-2H2]-tyrosine and ingested 35 g wheat protein (n= 12), 35 g wheat protein hydrolysate (n= 12), 35 g micellar casein (n= 12), 35 g whey protein (n= 12), or 60 g wheat protein hydrolysate (n= 12). Plasma and muscle samples were collected at regular intervals throughout the infusion. RESULTS: The postprandial rise in plasma essential amino acid concentrations was greater after the ingestion of 35 g whey protein compared to casein and wheat protein (P< 0.01). Myofibrillar protein synthesis rates increased after the ingestion of 35 g casein (P< 0.01), and postprandial myofibrillar protein synthesis rates were higher after the ingestion of casein compared to wheat protein (P= 0.03). Despite similar leucine content, the postprandial rise in plasma leucine concentrations was greater after the ingestion of 35 g whey protein compared to 60 g wheat protein hydrolysate (P< 0.01). Nevertheless, ingesting 60 g wheat protein hydrolysate increased myofibrillar protein synthesis rates above basal rates (P= 0.02).

CONCLUSION: The myofibrillar protein synthetic response to the ingestion of 35 g casein is greater when compared with an equal amount of wheat protein. Ingesting a larger amount of wheat protein substantially increases myofibrillar protein synthesis rates in healthy older males.