Research has documented that within the first 6 to 8 hours post exercise, competition, or training – the window of recovery – the combined intake of protein (PRO) and carbohydrate (CHO) per hour – based on body weight (kilograms), is the appropriate mode to accelerate glycogen repletion in the liver, muscles, and circulatory system.
The reasoning is the sum of the parts – carbohydrate and protein ingestion – may be greater than either component in isolation. However, research is somewhat inconsistent.
The physiological effect is caused by the insulinogenic effects, when a fast -digesting whey protein isolate – high in the essential, branch chain, anabolic amino acid leucine – is selected, as the post-recovery protein of choice.
It’s also reported that the optimum refeeding of carbohydrate over the 6 to 8-hour recovery window is 1.2 grams per kilogram (2.2 pounds) of body mass, while the optimum protein refeeding is roughly 0.3 grams per kilogram.
Yet, some research says that after a carbohydrate refeeding of greater than 0.8 g/kg/hour a saturation effect takes hold – with more being less, potentially negating the effects, if protein is added to the mix.
In a study – Co-Ingestion of Carbohydrate and Protein on Muscle Glycogen Synthesis After Exercise: A Meta-Analysis – which was reported in the February 2021issue of Medicine & Science in Sports & Exercise, researchers from the Military Nutrition Division, U.S. Army Research Institute of Environmental Medicine in Massachusetts, and the Oak Ridge Institute of Science and Education, in Tennessee, the primary objective was, “to aggregate results from multiple studies to characterize the effects of CHO-PRO on glycogen synthesis, during recovery from exercise compared with CHO alone.”
The meta-analysis (numerous similar studies), which included research from PubMed and the Cochrane Library database, took place in July of 2019 – with a second search in March of 2020. “The population, intervention, control, and outcome for this meta-analysis were healthy, trained or untrained men or women, CHO-PRO, CHO only, and glycogen synthesis, respectively,” commented the investigators.
According to the research group, “the primary outcome of this meta-analysis was that co-ingestion of CHO-PRO had no overall significant effect on postexercise glycogen synthesis compared with CHO alone. However, postexercise glycogen synthesis was enhanced, when the combined CHO-PRO treatment provided more total energy than CHO alone.
The researchers said that the, “data indicate(d) that increasing the energy content of postexercise nutrition by adding protein to carbohydrate, and not replacing carbohydrate for protein, is likely a primary stimulus for enhanced glycogen synthesis during recovery from exercise, when CHO-PRO are consumed together.
The researchers contend that, “matching the energy content provided in current sport nutrition recommendations for optimal glycogen recovery of 1.2 g/kg/hour by lowering carbohydrate to 0.9 g/kg/hour and adding back the equivalent amount of protein to 0.3 g/kg/hour may yield the most complete post-exercise recovery by not only maximizing glycogen synthesis, but also by stimulating muscle protein synthesis.”
In other words, a blend of 0.9 grams of CHO and 0.3 grams of PRO per kilogram of body weight per hour over the recovery window might be the optimum combination to accelerate recovery from intense exercise, training, or competition.
Consideration should also be on the optimum CHO and PRO selection to address any allergy or digestive constraints. Consulting a sport certified dietetic nutritionist is recommended.
Interested in reading more? Check out Protein Sources For Athletic Performance