"Yo, you gotta take your casein before bed so you stay anabolic. Steady flow of amino acids while I sleep." How many times have you heard that? How many people have showed you a study validating it? Finally, one exists.
Introduction: It is hypothesized that ingesting protein before sleep could be beneficial to increase plasma amino acid availability, stimulate skeletal muscle protein synthesis and increase whole-body protein balance during sleep. Thus, this group took 16 recreationally active young men and after a single bout of resistance training gave them either casein protein or a placebo before bed. This is the first study to look at the effect of ingesting casein protein immediately before sleep and subsequently seeing how it effects protein synthesis and protein balance overnight.
Methods: All subjects received a standard meal the evening before the test and a standardized diet throughout the experimental day. Tracers were implemented in this study which allows for measurements of certain molecule in the blood. A tracer is a molecular that contains radioactive isotopes that can be measured by machines to see the overall flux of the molecule throughout the body. In this study, the researchers traced radioactive amino acids (it’s safe because they are stable isotopes, trust me)throughout the night following the exercise protocol. The protocol consisted of leg extensions and leg press and was performed three hours before bed.
Results: After ingestion of protein before sleep, the total essential amino acid concentrations in the plasma increased rapidly and stayed higher throughout the night as compared to the placebo group. For the tracer, the amount of protein available from the plasma-derived amino acids was 50% higher in the protein ingestion group at time 7.5hrs after sleep compared to the placebo. Finally, whole-body protein synthesis rates were higher in the protein group versus the placebo group.
Discussion: It is evident that the casein protein was in fact digested and absorbed normally throughout the night because the tracer used in this case came directly from the casein protein shake. Not only did they observe and increase in whole-body protein synthesis with the blood plasma samples, but the group also showed an increase in synthetic rate by taking muscle biopsies as well. Of course this could not be confirmed throughout the night but only before bed otherwise the person would not be able to sleep when the biopsy was being performed. Also, it is important to keep in mind that this is an acute (one-time) bout of resistance training and not chronic (long-term).
- Casein protein at bedtime is effectively digested and absorbed which would lead to an increase in available amino acids from blood plasma overnight
- Casein protein at bedtime stimulates muscle protein synthesis rates which would increase overnight protein balance.