Although many athletes have a “more is better” philosophy regarding protein intake, recent research suggests there may be a limit to the benefit that can be obtained from ingesting protein.
Researchers from the United Kingdom hypothesized that there is a extent to how much protein synthesis can be elevated, even when blood levels of essential amino acids remain elevated.
They measured the time course of increased muscle protein synthesis after the ingestion of 45g of whey protein isolate. Blood levels of essential amino acids, particularly leucine, peaked after 60 minutes, and remained elevated three hours after ingestion.
Rates of muscle protein synthesis lagged slightly behind the increase in blood leucine, peaking at about 90 minutes after ingestion to levels that were three-fold higher than before the whey ingestion. After this peak, rates of protein synthesis rapidly returned to baseline despite continued availability of leucine inside the muscle.
The results clearly show that a serving of whey protein results in a marked but transient increase in protein synthesis.
The decline in protein synthesis in the face of increased plasma and muscle levels of leucine and other essential amino acids suggests that there may be a limit to the increase in muscle protein synthesis possible with a single serving of protein.
The results lead one to speculate that taking whey protein in multiple servings is a better strategy than taking just a single serving, although this has not been tested yet.