Whey increases muscle glycogen and improves performance
by Jeff S. Volek, Ph.D., R.D.
Whey protein ranks at the top of the list for promoting health and performance. Whey is actually a complex food with a variety of peptides and bioactive nutrients responsible for its numerous positive effects. Two new studies from Japan shed light on another exciting benefit of whey—it accelerates glucose uptake and glycogen synthesis after exercise. Glycogen is the storage form of carbohydrate in the body and plays a role in preventing fatigue and enhancing performance.
In the first set of experiments, researchers studied animals that performed exhaustive exercise to deplete muscle glycogen. Control animals received carbohydrates only after exercise, whereas four other groups received carbohydrates plus different forms of protein including whey, whey hydrolysates, branched-chain amino acids (BCAAs) and casein hydrolysates. Muscle glycogen levels measured two hours after exercise revealed the groups fed whey and whey hydrolysate had dramatic increases—nearly two-fold greater than the carbohydrate-only and casein hydrolysate groups.
To better understand why whey outperformed the other proteins, the same researchers studied specific BCAA dipeptides from beta-lactoglobulin, one of the main proteins in whey. Dipeptides are simply two amino acids linked together. They showed several dipeptides that included leucine increased glucose uptake into muscle and glycogen storage.
These experiments provide evidence that whey protein, specifically certain BCAA dipeptides, which are present in whey, positively impact glucose metabolism by increasing glucose uptake and accelerating glycogen synthesis after exercise. These studies also indicate that whey may be useful for both athletes and individuals with insulin resistance (e.g., those with impaired fasting glucose, metabolic syndrome or diabetes).