Effects of Ingesting Protein in Combination With Carbohydrate During Exercise on Endurance Performance: A Systematic Review With Meta-Analysis

Abstract

Coingestion of protein with carbohydrate has been shown to enhance muscle recovery, particularly after intense bouts of exercise. However, performance benefits of ingesting a protein-carbohydrate drink during exercise remains unclear. Therefore, we used a systematic review with meta-analysis to examine the influence of protein ingestion during exercise on subsequent endurance performance. Eleven qualifying studies were included that contained 3 time-trial and 8 time-to-exhaustion cycling protocols. Only 3 of these studies controlled for caloric content and contained an isocaloric trial. Of the 11, 4 reported significant differences between a control and protein trial; however, none of these were isocaloric studies. The 3 time-trial protocols showed no significant improvement with protein. The meta-analysis of the time-trial studies revealed no significant overall effect (p = 0.73), whereas meta-analysis of time-to-exhaustion studies revealed a significant effect (p = 0.008). Of the time-to-exhaustion trials, the isocaloric studies found no significant effect (p = 0.71), whereas the isocarbohydrate studies revealed a significant effect (p = 0.05). The average percent improvement with ingestion of protein was 9.0%. The isocarbohydrate studies reported an improvement of 10.5%, whereas the isocaloric studies revealed a 3.4% improvement. We conclude that compared to carbohydrate alone, coingestion of protein and carbohydrate during exercise demonstrated an ergogenic effect on endurance performance when assessed by time to exhaustion and also where supplements were matched for carbohydrate (isocarbohydrate). Thus, the ergogenic effect of protein seen in isocarbohydrate studies may be because of a generic effect of adding calories (fuel) as opposed to a unique benefit of protein. Further research is warranted before a clear conclusion can be drawn.

Increased Protein Intake in Military Special Operations

“…Whereas protein itself is generally an inefficient energy source that has a minimal contribution to the overall energy demands of exercise, its coingestion during prolonged exercise has demonstrated efficacy. A recent meta-analysis by Stearns et al (17) indicates that the addition of protein to carbohydrate was beneficial when the performance endpoint was time-to-exhaustion. The authors found no effects when the performance endpoint was a time trial; however, one could argue that the time-to-exhaustion format is more applicable to the special operator and mission demands.…”

No Effect of Protein Coingestion on Exogenous Glucose Oxidation during Exercise

“…Recently, interest in the role of protein coingestion with carbohydrate has led to the fmdings of increased endurance in blind end point time-to-exhaustion cycling tests (10,12,27,28) but equivocal outcornes in known end point time trials (6,18,22,29,32,35,36). Although sample size retnains limited.…”

Necesidades proteicas de los deportistas y pautas diétetico-nutricionales para la ganancia de masa muscular

“…Desde el punto de vista de la siología nutricional, los estudios deberían aportar información sobre el momento de la toma del suplemento, calidad de la proteína que se consume habitualmente en la dieta y la cantidad de HC diaria, ya que estos aspectos pueden ser determinantes para el aumento de la masa muscular 72,95,96 . Además, se debe tener en cuenta que no se ha demostrado de manera positiva que las proteínas o los suplementos de AA tengan in uencia en el rendimiento deportivo, y estas recomendaciones de suplementación deben dirigirse principalmente a la optimización de la respuesta a la formación y el periodo de recuperación después del ejercicio 89 .…”