Impact of Pre-Sleep Protein Consumption on Muscle Protein Synthesis
Overview of the Study
A recent research investigation focused on the potential benefits of protein intake before sleep for enhancing protein synthesis in skeletal muscles. As individuals age, their protein requirements increase significantly, with older adults needing around 40 grams of protein to achieve a 75% increase in protein synthesis. This necessity arises from metabolic changes affecting protein synthesis and breakdown. Notably, the addition of free leucine—an amino acid vital for protein synthesis—has been shown to amplify protein synthesis even with minimal protein intake.
Previous Findings
Earlier studies indicated that administering 40 grams of protein intragastrically during sleep could supply free amino acids necessary for overnight protein synthesis. However, this method may primarily benefit older adults who struggle to meet their protein needs and aim to preserve muscle mass, rather than serving as a practical approach for healthy individuals seeking to enhance muscle growth. Consequently, a study published in The Journal of Nutrition aimed to assess the effects of protein consumption before sleep on overnight protein synthesis.
Study Design and Methodology
Participant Selection
The study employed a double-blind, randomized design, involving 48 male participants. Depending on the protein intake assigned, participants were divided into four groups: one receiving 40 grams of casein, another receiving 20 grams of casein, a third group receiving 20 grams of casein with 1.5 grams of leucine, and a placebo group. To qualify, participants had to be over 65 years of age, possess a body mass index (BMI) between 20 and 30, and refrain from using protein supplements. They also needed to engage in an exercise program or have lost more than 3 kilograms in the preceding three months. Exclusion criteria included smoking, diabetes, and any conditions or medications affecting muscle metabolism or mobility.
Preparation for the Study
Participants were instructed to maintain a regular diet and avoid intense physical activity for up to two days before the trial. Following an overnight fast, researchers collected anthropometric data and baseline measurements for plasma glucose, insulin, and glucose tolerance. Each participant received a tailored diet comprising three meals and two snacks aligned with their caloric requirements. They then consumed a beverage containing either the assigned protein quantity or a placebo consisting of water and vanilla flavor.
Monitoring Sleep Quality
During the night, wrist monitors tracked various sleep metrics, including bedtime, wake-up time, sleep efficiency, and sleep-onset latency. Sleep quality was evaluated using the Pittsburgh Sleep Quality Index, which ranged from very poor to very good. Participants rated as having poor to very poor sleep were excluded from the analysis.
Results and Conclusions
Protein Intake and Muscle Synthesis
The study revealed that the rate of phenylalanine appearance in the bloodstream increased across all treatment groups, with the highest rate observed in the group consuming the most protein. Conversely, the appearance rate of phenylalanine declined in both the treatment and placebo groups.
In conclusion, the findings indicate that protein intake before sleep enhances muscle protein synthesis. Specifically, consuming at least 40 grams of protein increases the availability of amino acids in the plasma, which contributes to muscle protein synthesis. While the addition of 1.5 grams of leucine was based on previous studies suggesting it could enhance protein synthesis rates, this study found its effect to be minimal. Future research should explore the integration of physical activity with pre-sleep protein consumption to examine its long-term impact on muscle mass. Overall, the study highlights the potential of pre-sleep protein intake as a strategy for maintaining muscle mass in older adults.
Author and Reference
Written by Monica Naatey-Ahumah, BSc
Reference: Kouw, I.W., Holwerda, A.M., Trommelen, J., Kramer, I.F., Bastiaanse, J., Halson, S.L., Wodzig, W.K., Verdijk, L.B., & van Loon, L.J. (2017). Protein Ingestion Before Sleep Increases Overnight Muscle Protein Synthesis Rates in Healthy Older Men: A Randomized Controlled Trial. The Journal of Nutrition, https://doi.org/10.3945/jn.117.254532.