Body Position Modulates Gastric Emptying and Affects the Post-Prandial Rise in Plasma Amino Acid Concentrations Following Protein Ingestion in Humans.
Level 2 - randomized trial
Individual randomized crossover trial
PubMed 27089362 · doi:10.3390/nu8040221
What was done
In a randomized crossover study, 8 healthy young men (age 25 ± 2 years, BMI 23.9 ± 0.8 kg·m⁻²) ingested 22 g protein and 1.5 g paracetamol in an upright seated position (control) and in a -20° head-down tilted position (inversion). Blood samples were collected over 240 minutes post-prandial to determine gastric emptying rate via paracetamol absorption and post-prandial amino acid availability via plasma amino acid concentrations.
What was found
Gastric emptying and amino acid availability were significantly lower in the -20° head-down tilted position compared to the upright seated position: - Peak plasma paracetamol concentrations: 5.8 ± 1.1 vs. 10.0 ± 0.6 mg·L⁻¹ (p < 0.05) - Peak plasma leucine concentrations: 177 ± 15 vs. 236 ± 15 mmol·L⁻¹ (p < 0.05) - Plasma essential amino acid (EAA) response over 240 min: 31,956 ± 6,441 vs. 50,351 ± 4,015 AU (p < 0.05)
Why it matters
Body posture directly alters gastric emptying and systemic amino acid availability after protein ingestion, suggesting positioning could affect post-prandial protein handling in clinical and athletic settings.
Limits
The sample size was very small (n = 8) and restricted entirely to young, healthy males. Muscle protein synthesis was not directly measured, and a -20° head-down tilt represents an acute experimental condition rather than standard recumbent or bed-rest postures.
Cited by
- partial Consuming food while sitting upright stimulates gastric emptying, leading to faster circulating amino acid release and greater muscle protein synthesis stimulation compared to eating while lying down.