Intragastric protein administration stimulates overnight muscle protein synthesis in elderly men.
Level 2 - randomized trial
Individual randomized controlled trial
PubMed 21917635 · doi:10.1152/ajpendo.00321.2011
What was done
Sixteen healthy elderly men were randomly assigned to receive an intragastric bolus of intrinsically L-[1-13C]phenylalanine-labeled casein protein (PRO) or a placebo (PLA) during sleep. Continuous intravenous infusions of L-[ring-2H5]phenylalanine and L-[ring-2H2]tyrosine were administered to measure in vivo dietary protein digestion and absorption kinetics, overnight whole-body protein balance, and muscle protein fractional synthesis rates.
What was found
Exogenous phenylalanine appearance increased following protein administration. Overnight whole-body protein balance was significantly higher in the protein group than in the placebo group (11.8 ± 1.0 vs. 0.30 ± 0.1 μmol phenylalanine·kg⁻¹·h⁻¹; P < 0.05). Overnight muscle protein fractional synthesis rates were significantly elevated with protein compared to placebo (0.045 ± 0.002 vs. 0.029 ± 0.002%/h; P < 0.05), showing incorporation of dietary amino acids at a rate of 0.058 ± 0.006%/h.
Why it matters
The findings show that the gastrointestinal tract and skeletal muscle remain responsive to protein feeding during sleep in older adults. Delivering protein overnight improves overnight net protein balance and muscle protein synthesis, providing a targeted strategy to help mitigate age-related muscle loss.
Limits
The study was restricted to a small cohort of healthy older men (n = 16), excluding women, younger adults, and individuals with sarcopenia or chronic illness. The intervention evaluated acute, single-night tracer kinetics rather than sustained, long-term changes in muscle mass or physical performance. Intragastric feeding during sleep does not fully replicate standard oral pre-sleep dietary habits.
Cited by
- supports Studies by Luc van Loon show that ingesting a bolus of protein directly before sleep increases overnight muscle protein synthesis.