Sipping casein protein doubles the muscle-building effect compared to whey protein

The milk proteins whey and casein are both excellent sources of all the essential amino acids. One distinguishing feature is their digestion rate. When consumed in a bolus, whey leaves the stomach quickly resulting in a rapid increase in blood amino acids. Casein, on the other hand, stays in the stomach longer and results in a much slower rate of absorption.

These differences in digestion rate have been shown in many studies to alter the effect on protein balance in the body. In most studies, whey produces a slightly stronger effect than casein because of the rapid increase in essential amino acids that stimulate a robust increase in muscle protein synthesis. However, according to results of a recently published study, the role of digestion rate may be altered if protein supplements are sipped rather than consumed in a single bolus.

Healthy subjects were studied over a 5 hour period during which time they consumed 30 grams of either whey or casein. The protein drinks were sipped every 20 min during the study period (14 ingestions). Subjects also performed cycle exercise for 20 min on two occasions during the five hour protocol. Blood levels of branched chain amino acids were approximately 10% higher curing casein than whey. Measures of net whole body protein synthesis were consistently about 2-fold higher during the casein than the whey.

These interesting results suggest that the way protein drinks are ingested may alter how they are processed. Specifically, when sipping protein supplements, casein has a greater anabolic effect over whey. 

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