Several recent publications indicate that the maximum stimulation of muscle protein fractional synthetic rate occurs with intake of 20-30 g protein. This finding has led to the concept that there is a maximal anabolic response to protein intake with a meal, and that the normal amount of protein eaten with dinner will generally exceed the maximally-effective intake of protein. However, protein breakdown has not been taken into account when evaluating the anabolic response to protein intake. Protein anabolism occurs only when protein synthesis exceeds protein breakdown. Higher protein intakes when protein synthesis is maximized is characterized by suppressed protein breakdown and via that mechanism leads to a greater anabolic response. This explains why when net protein synthesis is measured, the relationship between amino acid availability and net gain remains linear, without any apparent plateau of effect at higher levels of availability. We conclude that there is no practical upper limit to the anabolic response to protein or amino acid intake in the context of a meal.
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