Long-lasting Improved Amino Acid Bioavailability Associated with Protein Pulse Feeding in Hospitalized Elderly Patients: a Randomized Controlled Trial

Objective: Aging is associated with a blunted anabolic response to dietary intake, possibly related to a decrease in systemically available amino acids (AAs), which in turn may stem from increased splanchnic AA metabolism. Splanchnic sequestration can be saturated by pulse feeding (80% of daily protein intake in a single meal), enabling increased protein synthesis. The aim of this study was to explore whether protein pulse feeding increased postprandial AA concentrations, and if so whether this increase persisted after 6 wk of dietary treatment.

Methods: This prospective randomized study enrolled 66 elderly malnourished or at-risk patients in an inpatient rehabilitation unit. All were given a controlled diet for 6 wk. In a spread diet (SD) group (n = 36), dietary protein was spread over the four daily meals. In a pulse diet (PD) group (n = 30), 72% of dietary protein (averaging 1.31 g/kg body weight daily) was consumed in one meal at noon. The patients were evaluated on day 1 and at 6 wk for plasma postprandial (five times from 0 to +180 min) AA concentrations (expressed as area under the curve above baseline).

Results: Protein pulse feeding was more efficient than protein spread feeding at increasing plasma postprandial AA concentrations, notably of essential AAs. This increased postprandial AA bioavailability was maintained after 6 wk.

Conclusions: This study demonstrates that increased postprandial AA bioavailability induced by protein pulse feeding persists after 6 wk (i.e., that there is no metabolic adaptation blunting AA bioavailability).