The Difference Between Whey & Casein

Whey and casein both come from milk. Whole milk contains approximately 80 percent casein and 20 percent whey, according to the Whey Protein Institute. Both forms of dairy protein offer complete protein with all the essential amino acids. Whey and casein come in powdered form for use as a nutritional supplement. The rate of absorption is the main difference between these two forms of dairy protein.

Background

Cheese making results in whey, the liquid left over when milk becomes curds for cheese. Manufacturers filter the whey to produce whey protein. Whey protein isolate contains a minimum of 90 percent protein and little or no fat and lactose, according to the Whey Protein Institute. Whey protein concentrate includes 29 percent to 89 percent protein and higher levels of carbohydrate than whey isolate due to its lactose content. Lactose is a naturally occurring milk sugar.

Research

Both whey and casein result in similar muscle protein synthesis when consumed post-exercise, according to researchers from the University of Texas Medical Branch who published their findings in the December 2004 "Medicine & Science in Sports & Exercise." The researchers concluded that amino acid uptake was similar for casein and whey. A post-workout drinking containing whey, casein or a combination of proteins can help to reduce the risk of muscle breakdown and promote muscle growth.

Benefits

Whey proteins provide the highest biological value, BV, of any protein. Your body absorbs and uses whey protein more effectively than other protein sources, according to dietitian Amy Kosowski at the Natural Health Research Institute. In addition to being a higher quality protein source, it's more soluble than casein, meaning it dissolves better in liquids.

Casein digests more slowly than whey for sustained energy. Because of its slow absorption rate, it serves as a good choice for a bedtime meal or for when you have a long wait for your next meal.

Considerations

The average American consumes enough protein from dietary sources. The Recommended Dietary Allowance for protein is 0.8 g per kilogram of body weight.

Preliminary research indicates that whey protein may help people with AIDS gain weight, MayoClinic.com reports. Because liquid calories are less filling than solid food, shakes and smoothies made with whey, casein or a combination of whey and casein can provide supplemental nutrition for people with poor appetites. People with lactose intolerance or dairy allergies should consult their doctor before consuming whey or casein.