Raw Eggs to Support Post-Exercise Recovery in Healthy Young Men: Did Rocky Get It Right or Wrong?

Abstract
Background: Egg protein is ingested during recovery from exercise to facilitate the post-exercise increase in muscle protein synthesis rates and, as such, to support the skeletal muscle adaptive response to exercise training. The impact of cooking egg protein on post-exercise muscle protein synthesis is unknown.

Objectives: To compare the impact of ingesting unboiled (raw) versus boiled eggs during post-exercise recovery on postprandial myofibrillar protein synthesis rates.

Methods: In a parallel design, forty-five healthy, resistance trained young men (age: 24 (95%CI: 23-25) y) were randomly assigned to ingest 5 raw eggs (∼30 g protein), 5 boiled eggs (∼30 g protein), or a control breakfast (∼5 g protein) during recovery from a single session of whole-body resistance-type exercise. Primed continuous L-[ring-13C6]-phenylalanine infusions were applied, with frequent blood sampling. Muscle biopsies were collected immediately after cessation of resistance exercise and at 2 and 5 h into the post-exercise recovery period. Primary (myofibrillar protein synthesis rates) and secondary (plasma amino acid concentrations) outcomes were analyzed using repeated-measures (Time*Group) ANOVA.

Results: Ingestion of eggs significantly increased plasma essential amino acid concentrations, with 20% higher peak concentrations following ingestion of boiled compared with raw eggs (Time*Group: P < 0.001). Myofibrillar protein synthesis rates were significantly increased during the post-exercise period when compared to basal, post-absorptive values in all groups (2-4 fold increase: P < 0.001). Postprandial myofibrillar protein synthesis rates were 20% higher after ingesting raw eggs (0.067%/h (95%CI:0.056-0.077); effect size (Cohen's d): 0.63), and 18% higher after ingesting boiled eggs (0.065%/h (95%CI:0.058-0.073); effect size: 0.69) when compared to the control breakfast (0.056%/h (95%CI:0.048-0.063), with no significant differences between groups (Time*Group: P = 0.077).

Conclusions: The ingestion of raw, as opposed to boiled, eggs attenuates the postprandial rise in circulating essential amino acid concentrations. However, post-exercise muscle protein synthesis rates do not differ after ingestion of 5 raw versus 5 boiled eggs in healthy young men. Trial registration: NL6506.

Keywords: absorption; anabolism; boiled eggs; cooked eggs; digestion; egg protein; food processing; muscle protein synthesis; preheating; resistance exercise.