Protein Ingestion before Sleep Increases Overnight Muscle Protein Synthesis Rates in Healthy Older Men: A Randomized Controlled Trial.
Level 2 - randomized trial
Individual randomized controlled trial
PubMed 28855419 · doi:10.3945/jn.117.254532
What was done
In a randomized, double-blind, parallel-group trial, 48 healthy older men (mean ± SEM age: 72 ± 1 years) ingested one of four drinks before sleep: 40 g casein (PRO40), 20 g casein (PRO20), 20 g casein plus 1.5 g leucine (PRO20+LEU), or a placebo. Ingestion of intrinsically l-[1-13C]-phenylalanine- and l-[1-13C]-leucine-labeled protein was combined with intravenous infusions of l-[ring-2H5]-phenylalanine and l-[1-13C]-leucine to measure overnight dietary protein digestion, absorption kinetics, and myofibrillar protein synthesis rates from blood and muscle biopsy samples.
What was found
Exogenous phenylalanine appearance rates rose more after PRO40 than after PRO20 and PRO20+LEU (P < 0.05). Overnight myofibrillar protein synthesis rates (phenylalanine tracer) were 0.033% ± 0.002%/h in placebo, 0.037% ± 0.003%/h in PRO20, 0.039% ± 0.002%/h in PRO20+LEU, and 0.044% ± 0.003%/h in PRO40, with PRO40 significantly higher than placebo (P = 0.02). Leucine-based synthesis rates were 0.047% ± 0.004%/h for placebo versus 0.058% ± 0.003%/h for PRO40 (P = 0.08). Incorporation of dietary amino acids into myofibrillar protein was greater in PRO40 (0.033 ± 0.002 MPE) than in PRO20 (0.019 ± 0.002 MPE, P < 0.001) and tended to be higher than in PRO20+LEU (0.025 ± 0.002 MPE, P = 0.06).
Why it matters
This study demonstrates that presleep protein is effectively digested and absorbed throughout the night in older adults, showing that 40 g of casein stimulates overnight muscle protein synthesis to help offset age-related anabolic resistance.
Limits
The sample size is modest (48 participants across four parallel arms, ~12 per group) and restricted entirely to healthy older men. It is an acute, single-night physiological study measuring fractional synthetic rate proxies rather than long-term gains in muscle mass, function, or strength.
Cited by
- supports Studies by Luc van Loon show that ingesting a bolus of protein directly before sleep increases overnight muscle protein synthesis.