Update on maximal anabolic response to dietary protein

The anabolic response to dietary protein can be defined as the difference between protein synthesis and breakdown, or the net protein balance, in response to ingestion of protein alone or a mixed meal containing protein. Others have concluded that a maximal anabolic response can be achieved with ingestion of 20-35 g of a high quality protein, leading to the formulation of a popular concept that the maximal anabolic response can be achieved by distributing the total protein intake evenly throughout the day, rather than eating a majority of dietary protein with dinner. However, this concept was based entirely on the measurement of muscle protein synthesis and thus ignored the potential contributions of suppression of protein breakdown to the anabolic response, as well as the possibility that tissues and organs other than muscle may also play a role in the anabolic response. In this review we discuss the factors comprising the total anabolic response, discuss relevant methodological issues, derive a theoretical maximal anabolic response based on current literature values, and interpret recent papers addressing the issue of maximal anabolic response as well as meal distribution of dietary protein. We conclude that it is not likely that there is a practical limit to the maximal anabolic response to a single meal, and the most efficient way in which to maximize the total anabolic response over a 24-h period is to increase dietary protein at breakfast and lunch without reducing protein intake with dinner.