It’s common knowledge among most bodybuilders that casein is the “nighttime protein”—a slow-digesting alternative to whey for staving off catabolism while we sleep. Yet, amazingly, there have been no studies conducted specifically to address this claim—until now, and it’s good news.
The latest research, and first ever of its kind, was conducted at Maastricht University Medical Center in the Netherlands. Researchers had 16 healthy males perform an hour of resis tance training at 8 p.m., following a day of standardized eating, and then consume 20 grams of whey protein and 60 grams of carbs immediately after. Then, at 11:30 p.m.—a half hour before bedtime—the group was split into two: Half of the subjects were given a shake containing 40 grams of casein protein, while the other half received one without. Then, while both groups slept, the researchers monitored them throughout the night via intravenous transfusions, paying specific attention to protein digestion, absorption kinetics, whole-body protein balance, and muscle protein synthesis rates.
They found a rapid and sustained rise in circulating amino acid levels across the group that consumed casein before bed, indicating that the protein was both effectively digested and absorbed. These subjects showed higher whole-body protein synthesis rates—approximately 20% better than the group that went without—as well as improved net protein balance.
So there you have it: Cold, hard scientific evidence that not only is nighttime casein both effectively digested and absorbed, but it is also a surefire way to stimulate muscle protein synthesis and fight off catabolism during the hours spent sleeping after resistance training.
REFERENCE: P.T. Res et al., Med Sci Sports Exerc., E-pub ahead of print, 2012.