Whey Protein Enhances Muscle and Liver Glycogen Storage – Implications For Muscle Growth and Exercise Recovery.
Even in academic circles, dietary protein is often simplistically viewed as a mere source of amino acid “building blocks” for the body’s tissues and enzymes. Decades’ worth of research clearly shows, however, that certain food proteins and peptides exert remarkable biological effects independent of their role in forming the structural material of tissues and enzymes.
Dairy proteins – and whey proteins in particular – happen to be among the richest sources of such bioactive peptides. In previous Integrated Supplements Blog articles, for example, we’ve examined how the potent antioxidant activity of whey’s cysteine-containing peptides may be of unique benefit in conditions characterized by oxidative stress such as diabetes:
We’ve seen how the iron-binding properties of whey’s lactoferrin peptide may protect against iron-induced oxidative damage:
And, we’ve seen how the whey peptide called glycomacropeptide may suppress appetite, ultimately leading to reduced caloric intake:
As it turns out, even the muscle-building properties of whey protein aren’t solely due to protein’s role as a structural component of muscle tissue. Whey protein may have the unique ability to facilitate the uptake and storage of carbohydrate in the body’s cells – thus creating the optimal environment for exercise recovery and muscle growth.
Muscle and Liver Glycogen – Keys to Exercise Performance, Recovery, and Muscle Building
Glycogen is the storage form of carbohydrate found in the body’s cells. When energy demands are taxed – as they are in intense exercise – levels of muscle glycogen and the “emergency reserve” of liver glycogen become drained. In this scenario, not only does performance suffer (glycogen depletion is thought to be a major factor in the fatigue of endurance athletes, for example), but recovery from training is hindered as well. This is why the muscle-building effects of weight training are often hindered by inadequate nutrition. In other words, no matter how much protein is consumed, muscle protein synthesis (i.e., muscle growth) simply cannot occur optimally until glycogen stores are replenished.
In fact, monitoring the level of liver glycogen may be a fundamental way in which the body gauges a fed state (i.e., a metabolic environment suitable for growth and repair). When liver glycogen is low, the body may elicit the adrenaline-driven “fight-or-flight” response which converts structural (e.g., muscle) proteins into fuel sources – obviously, not the ideal situation for muscle growth.
Note – the role of liver glycogen as a signal of the fed state is outlined in our article:
Whey Protein Increases Glycogen Levels
Recent research has shown that whey protein may be unique among protein sources in facilitating the uptake and storage of muscle and liver glycogen.
Human studies have shown that mixtures of whey and casein protein combined with carbohydrates led to significantly greater rates of glycogen storage relative to either carbohydrate or protein alone:
Quote from the above study:
The rate of muscle glycogen storage during the CHO-PRO treatment [35.5 +/- 3.3 (SE) mumol.g protein-1.h-1] was significantly faster than during the CHO treatment (25.6 +/- 2.3 mumol.g protein-1.h-1), which was significantly faster than during the PRO treatment (7.6 +/- 1.4 mumol.g protein-1.h-1). The results suggest that postexercise muscle glycogen storage can be enhanced with a carbohydrate-protein supplement as a result of the interaction of carbohydrate and protein on insulin secretion.
Subsequent animal studies have found that whey protein (more so than casein) is uniquely responsible for increasing glycogen levels after exercise.
Quote from the above study:
Total glycogen synthase activity in the skeletal muscle in the whey protein group was significantly higher than that in the casein group. The present study is the first to demonstrate that a diet based on whey protein may increase glycogen content in liver and skeletal muscle of exercise-trained rats.
In all, it seems that whey protein along with a source of carbohydrates (including some fructose) – consumed either before or after workouts – is the ideal way to maximize the muscle-building effects of exercise.
Ideally, the whey protein chosen will contain the full spectrum of whey’s bioactive peptides, be all-natural, and free of residual amounts of cholesterol – as is Integrated Supplements CFM® Whey Protein Isolate.