Consumption of High-Leucine-Containing Protein Bar Following Breakfast Impacts Aminoacidemia and Subjective Appetite in Older Persons

Abstract

Background: Limited data are available examining dietary interventions for optimizing protein and leucine intake to stimulate muscle protein synthesis (MPS) in older humans.

Objectives: We aimed to investigate the aminoacidemia and appetite responses of older adults after consuming breakfast, a meal frequently consumed with high-carbohydrate and below-par amounts of protein and leucine for stimulating MPS.

Methods: Five men and 3 women (means ± SD; age: 74 ± 7 y, BMI: 25.7 ± 4.9 kg/m², fat- and bone-free mass: 63 ± 7 kg) took part in this experiment in which they consumed breakfasts with low-protein (LP = 13 ± 2 g), high-protein (HP = 32 ± 5 g), and LP followed by a protein- and leucine-enriched bar formulation 2 h later (LP + Bar = 29 ± 2 g). The LP, HP, and LP + Bar breakfast conditions contained 519 ± 86 kcal, 535 ± 83 kcal, and 739 ± 86 kcal, respectively. Blood samples were drawn for 6 h and analyzed for amino acid, insulin, and glucose concentrations. Visual analog scales were assessed for hunger, fullness, and desire to eat.

Results: The net AUC for essential amino acid (EAA) exposure was similar between the LP + Bar and HP conditions but greater in the HP condition compared with the LP condition. Peak leucinemia was higher in the LP + Bar condition compared with the HP, and both were greater than the LP condition. Net leucine exposure was similar between HP and LP + Bar, and both were greater than LP. Hunger was similarly reduced in LP + Bar and HP, and LP + Bar resulted in a greater hunger reduction than LP. Both LP + Bar and HP resulted in greater net fullness scores than LP.

Conclusions: Consuming our bar formulation increased blood leucine availability and net exposure to EAAs to a similar degree as consuming a high-protein meal. High-protein at breakfast results in a greater net exposure to EAAs and leucine, which could support MPS in older persons. This study was registered at clinicaltrials.gov as NCT03712761.

Keywords: aging; amino acids; dietary intervention; milk protein; muscle preservation; randomized trial; sarcopenia; satiety; supplement.

FIGURE 1

Breakfast meals. (A) Lower-protein-containing breakfast and protein- and leucine-enriched bar (red circle). (B) Higher-protein-containing breakfast without the bar.

FIGURE 2

Plasma leucine (A), branched-chain amino acid (BCAA; B), and essential amino acid (EAA; C) concentrations (μM) in the fasting state and after the ingestion of a lower-protein breakfast containing 9–16 g protein (LP), higher-protein breakfast containing 23–40 g protein (HP), or a protein- and leucine-enriched bar containing ∼16 g protein ingested 2 h after consuming LP (LP + Bar) in healthy older men and women. Values are means ± SEM, n = 8 per treatment. *LP significantly different from HP (P < 0.05). ^†LP significantly different from LP + Bar (P < 0.05). #HP significantly different from LP + Bar (P < 0.05).

FIGURE 3

The effects of a protein-and leucine-enriched bar on the desire to eat (A and D), hunger (B and E), and fullness (C and F) [mm and mm·360 min⁻¹(6 h)] in the fasting state and after the ingestion of a lower-protein breakfast containing 9–16 g protein (LP), a higher-protein breakfast containing 23–40 g protein (HP), or a protein- and leucine-enriched bar containing ∼16 g protein and 220 kcal ingested 2 h after consuming LP (LP + Bar) in healthy older men and women. VAS values are means (error bars on VAS scores are omitted for clarity), n = 8 per treatment. Net AUC values are presented as box-and-whisker plots with the whiskers showing maximum and minimum values, the box the IQR, the cross (+) shows the mean, and the line is the median. *Significantly different from LP (P < 0.05). VAS, visual analog scale.