Older Adults Have Delayed Amino Acid Absorption after a High Protein Mixed Breakfast Meal.
Level 3 - non-randomized controlled study
Cross-sectional comparative cohort study with matched controls
PubMed 26412288 · doi:10.1007/s12603-015-0500-5
What was done
In a clinical research setting, researchers compared 15 healthy older adults (aged 60–75 years) with 15 healthy younger adults (aged 20–25 years) matched for body mass index and insulin sensitivity (HOMA-IR). Participants consumed a high-protein mixed meal made of complete food products. Circulating plasma amino acid concentrations were measured hourly at baseline and for 5 hours postprandially.
What was found
Total area under the curve (AUC) for individual amino acids and amino acid classes did not differ significantly between cohorts, nor did the appearance of non-essential amino acids. However, baseline concentrations differed: older adults had higher baseline levels of aspartic acid, glutamic acid, glycine, ornithine, threonine, and tyrosine, and lower baseline levels of hydroxyproline, isoleucine, leucine, methionine, and valine. Peak essential amino acid (EAA) and branched-chain amino acid (BCAA) concentrations occurred at 1 hour post-meal in younger adults versus 3 hours post-meal in older adults. Peak total amino acid concentrations also occurred at 3 hours in older adults.
Why it matters
This study indicates that while total postprandial amino acid absorption from a whole-food meal is preserved in healthy older adults, the absorption kinetics are substantially delayed.
Limits
The study had a small sample size (n=15 per group) and only evaluated healthy individuals across a 5-hour window following a single meal. Muscle protein synthesis, gastric emptying, and splanchnic extraction were not directly measured to confirm clinical or functional outcomes.
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