What’s the Difference Between Casein and Whey?

July 06, 2016

You’re probably familiar with the fact that milk has high-quality protein. But did you know milk actually has two main types of protein?

Approximately 80 percent of the protein in milk is casein protein, while the other 20 percent is whey protein.

Both whey and casein are high-quality, complete proteins. However subtle differences in amino acid composition and rate of digestion might impact how and when you decide to use them.

Casein is often referred to as a “slow” protein due to its slower rate of digestion which results in a more gradual and prolonged release of amino acids to muscle. Recently, scientists have hypothesized that taking casein before bed may help maximize muscle rebuilding, repair and recovery after exercise as its slow release of amino acids may be advantageous for the overnight period where the next meal may be 8-12 hours away. To date, two studies in healthy young men performing resistance exercise have shown improved recovery (muscle protein synthesis) and greater gains in muscle mass when casein was provided prior to sleep compared to no protein after exercise. While protein is important for athletes post-exercise (ACSM/AND position statement 2016), more research is needed on the timing of protein consumption and muscle benefits.

Whey protein, typically available as whey protein concentrate 80 (WPC 80) or whey protein isolate (WPI) is often referred to as a “fast” protein due to its rapid, more transient (compared to casein) release of amino acids to the muscle. WPC 80 contains 80 percent protein by dry weight, while WPI typically contains 90-93 percent protein by dry weight.

Given its one of the most concentrated sources of leucine (a key amino acid in promoting muscle protein synthesis) among protein containing foods (providing about 2.5 grams of leucine per 20 grams of protein) along with its rapid digestibility, some experts have noted whey as the protein of choice right after a tough workout. Additionally WPI can contain minimal amounts of lactose, depending on which product is used, so some brands of WPI  may be a good option for lactose intolerant individuals.* 

These proteins can be removed from milk, dried into a powder and used as an ingredient providing high-quality protein to a number of food and beverages. A growing body of research supports benefits of higher-protein diets for athletes and highly active adults, weight management and to foster healthy aging.

In addition to using these dairy proteins in their powdered form, you can also enjoy them in dairy foods.

As people look for ways to add high-quality protein to their diets, protein powders are becoming more mainstream. Once thought of simply as a muscle building supplement to have post workout, people are beginning to embrace the versatility and convenience of protein powders as an ingredient to increase the protein content of some of their favorite dishes.


* As FDA specifications for WPI allow for up to 6 percent lactose


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