(P25-044-25) Plasma Leucinemia Following a Leucine-Enriched Whey-Casein Blend in Younger and Mid-aged Adults

Objectives: Leucine is essential for stimulating skeletal muscle anabolism and requires a specific dose to activate muscle protein synthesis. In contrast to whey protein, which is digested quickly, micellar casein precipitates in the stomach. Casein is digested more slowly, leading to a moderate yet prolonged increase in amino acids in the bloodstream. In this study, we aimed to evaluate postprandial aminoacidemia after consuming equal amounts of protein (25 g) from four different sources: whey protein (Whey), micellar casein (Mcas), a 1:1 blend of whey protein and micellar casein (Blend), and a 1:1 blend of whey protein and micellar casein with added free crystalline leucine (LEUCY study product). We hypothesized a gradual increase in leucinemia across the four groups from the early postprandial phase through to the later postprandial phase.

Methods: We compared plasma leucine parameters between conditions over a 240-minute post-feeding period through serial blood draws for amino acid analysis. The participants included a diverse sample of younger to middle-aged males and females (mean ± SD; age: 32 ± 15 [age range: 19 to 58 years], body weight: 79 ± 19 kg, height: 177 ± 11 cm).

Results: Compared to the other three conditions, the LEUCY group exhibited a slightly higher plasma leucine level at 30 minutes (% from baseline) (371% [317-460]), but this was not significantly different from the Whey (340% [217-422]) or the Blend (308% [227-382]) groups. However, the Whey, Blend, and LEUCY groups were all significantly higher than Mcas (232% [197-249]). The total area under the curve (AUC) for plasma leucine concentration during the 240-minute post-feeding period displayed a similar pattern, with LEUCY showing a slightly higher level but not significantly different from the Whey and Blend AUC (16808, 15643, and 17280, respectively). Once again, the leucine AUC for Mcas (10388) was significantly lower than the other three conditions.

Conclusions: Our data indicates that LEUCY leads to higher leucinemia during the early postprandial phase and a slightly elevated leucine concentration over the 240-minute post-feeding period compared to the other tested protein supplements.

Funding Sources: Nutraceutical Innovations LLC supported this study.