Woman Drinking Protein Powder

The Ins and Outs of Casein Protein

Education Objectives:

  • Protein and its impact on health and performance
  • Protein types and how to make sound decisions surrounding protein types

What is Protein and Why Is it Important?

Macronutrients are key nutrients needed by our body in large amounts (macro is a prefix that means ’large’) and include carbohydrate, proteins, and fats. Of these, protein is the only macronutrient that isn’t stored across our body and instead is utilized by all of our cells to build and rebuild parts of new cells, tissues, etc.

Several types of protein exist and when ranked using traditional rating schema, animal proteins, such as beef, chicken, turkey, fish, eggs, milk, and other ‘flesh proteins’, routinely rank as the highest quality. While animal proteins are key parts of many meals across a typical American diet, milk contains two proteins that are highly regarded as well: whey and casein.

Did you know that traditional bovine (cow) milk, if separated, is composed of 80% casein and 20% whey…a natural blend of two different animal proteins (more on that later).

What is Casein?

Casein protein is a relatively high-quality source of protein with a healthy supply of amino acids, including the critically important essential amino acids.

While this sounds encouraging, in many aspects of dairy production, casein is a waste product. Discarded. Thrown away. Talk about a ‘yin’ and a ‘yang’ perspective on something.

This may get you thinking, if casein is a waste product to some people, why should I care about it? Nutrition researchers for 20+ years now have researched how casein behaves after we consume it in comparison to whey protein and stark, yet meaningful differences have been well documented.

For example, in the late 1990s, Yves Boire et al. (1) and Dangin and colleagues (2, 3) couple of research studies that have since changed the way in which we talk about both whey and casein protein.

For starters, whey and casein protein exhibited different protein digestion rates largely due to differences in how soluble they are in the acidic environment of the stomach. Put simply whey protein digestion occurs at a faster rate while casein protein digests slower.

One of the key outcomes that results from knowing that whey and casein digest at different rates is their resulting impact on muscle protein synthesis and breakdown (4). While whey protein is viewed favorably for its powerful anabolic response upon ingestion, one must remember that casein protein still causes sharp and significant increases in muscle protein synthesis.

A key point, however, that most people overlook is that casein does a much better job of preventing increases in muscle protein breakdown when compared to whey protein. When viewed over the course of several hours, casein protein promotes a longer and greater anabolic profile when compared to whey protein (2, 3).

How and Where Does Casein Fit?

So where and how should someone integrate casein protein into their regimen? My first recommendation is to focus less on what type of protein you are consuming and more on the total amount of protein you are consuming while also making sure you are getting an number of calories that meets your exercise goals. While this topic is a popular one and one worth addressing, it is a bit beyond the scope of this article.

News flash: one gram of protein per pound of body mass is a great goal for most people to strive to hit each day and this recommendation falls in line with guidelines from the International Society of Sports Nutrition (5) and other key professional organizations (6).

From here, I will point to two examples where some scientific approaches have solidified our understanding of how casein can be a part of a daily goal of reducing body fat and improving strength and function of our body.

Practical Application #1 – The Power of Blending Whey and Casein

The first example outlines a research study I helped to conduct during my master’s degree at the University of Memphis.

We conducted a 10-week resistance study where we recruited healthy men and women who were already regularly resistance training and had them all follow a 4 day per week resistance training program that was split into two upper-body workouts and two lower-body workouts (7).

We assessed strength, endurance, power, and body composition (muscle mass and fat mass) before and at the end of the 10-week study. The cool part was that we also split all study participants up into three groups and had one group supplement with 48 grams of carbohydrate (this was our placebo group), 40 grams of whey protein and 8 grams of casein protein (this was our protein control group), and 40 grams of whey, 5 grams of glutamine, and 3 grams of branched-chain amino acids (this was our experimental group).

Consider closely that all groups supplemented with the same amount of calories and the two groups that received protein were given the same amount of protein (48 grams). The study was designed to ideally demonstrate the superior benefits of the whey + glutamine + BCAA group, but instead we found that the protein control group (the blend of whey and casein) was responsible for the greatest improvements in fat-free mass, body fat percentage, and strength outcomes.

Why did this happen? We hypothesized that the combination of whey and casein led to a favorable combination of fast and slow proteins that created an ideal environment for positive changes.

In other words, this group provided just enough of the favorable properties of casein that helped to prevent muscle breakdown while also providing enough whey protein to stimulate increases in protein growth. What does a pretty good job of matching this combination?

Mixing a whey protein powder with low-fat milk. So before you think you are doing yourself a favor by only mixing your whey protein with water because you are maximizing delivery of highly anabolic whey protein, consider that providing a little milk will also deliver valuable casein protein that may help to prevent muscle protein breakdown.

Practical Application Example #2 - Casein Protein and Night-Time Feeding

Currently, the most advocated area for casein protein is during the night-time period. While not traditionally viewed as a key time to consider strategic feeding, several studies have recently demonstrated that eating a small meal (200 – 300 kcals) that is nearly exclusively casein protein may help promote recovery from exercise and can also serve as an excellent to time to meet daily protein needs.

One of the first studies in this space indicated that regular ingestion of protein before sleep in comparison to consuming a noncaloric placebo increases muscle mass and strength after several weeks. While a definite shortcoming of this study was the differences in energy intake and protein intake between the groups, these initial findings sparked excitement that eating protein before bed could indeed boost training outcomes.

From there, a key finding demonstrated that night-time feeding of a 40-50 gram dose of protein does not change overnight rates of fat production (8), an often cited fear of eating late at night. In addition, other studies have indicated that a dose of pre-sleep protein may improve overnight recovery (9) and may augment exercise training adaptations (10).

Wrapping It Up

So where does that leave us? First, protein is a key nutrient that exercising people need more of and is a challenge for some to get in appropriate amounts.

Casein is a high-quality protein found in milk that digests slow and does a good job of promoting increases rates of muscle protein growth, but is exceptional at preventing increases in muscle protein breakdown, which overall creates a favorable balance of muscle protein metabolism.

Casein is found in high amounts in dairy such as milk and cottage cheese. Consuming a healthy dose of casein (40-50 grams) or other high-quality protein sources before bed while dieting and/or training may help one to achieve their daily protein goal and promote optimal muscle growth and recovery.

About the Author

Chad Kerksick is currently an Associate Professor of Exercise Science and Director of the Exercise and Performance Nutrition Laboratory at Lindenwood University. Dr. Kerksick earned his PhD in Exercise, Nutrition, and Preventive Health in 2006. Since that time has worked as a university professor teaching classes and conducting research in areas related to exercise and nutrition. His laboratory, the Exercise and Performance Nutrition Laboratory (www.lindenwood.edu/EPNL), conducts rigorous, high-quality research investigations devoted to examining the impact of exercise and nutritional interventions of health, performance, and recovery of a large number of populations. Chad has worked with 1st Phorm since 2010 providing educational content in multiple formats, assisting with educational events, and providing feedback for formulations and labeling.


1. Boirie Y, Dangin M, Gachon P, Vasson MP, Maubois JL, Beaufrere B. Slow and fast dietary proteins differently modulate postprandial protein accretion. Proc Natl Acad Sci U S A. 1997;94(26):14930-5.

2. Dangin M, Boirie Y, Garcia-Rodenas C, Gachon P, Fauquant J, Callier P, et al. The digestion rate of protein is an independent regulating factor of postprandial protein retention. Am J Physiol Endocrinol Metab. 2001;280(2):E340-8.

3. Dangin M, Boirie Y, Guillet C, Beaufrere B. Influence of the protein digestion rate on protein turnover in young and elderly subjects. J Nutr. 2002;132(10):3228S-33S.

4. Tang JE, Moore DR, Kujbida GW, Tarnopolsky MA, Phillips SM. Ingestion of whey hydrolysate, casein, or soy protein isolate: effects on mixed muscle protein synthesis at rest and following resistance exercise in young men. J Appl Physiol. 2009;107(3):987-92.

5. Jager R, Kerksick CM, Campbell BI, Cribb PJ, Wells SD, Skwiat TM, et al. International Society of Sports Nutrition Position Stand: protein and exercise. J Int Soc Sports Nutr. 2017;14:20.

6. Thomas DT, Erdman KA, Burke LM. Position of the academy of nutrition and dietetics, dietitians of Canada, and the American college of sports medicine: nutrition and athletic performance. Journal of the Academy of Nutrition and Dietetics. 2016;116.

7. Kerksick CM, Rasmussen CJ, Lancaster SL, Magu B, Smith P, Melton C, et al. The effects of protein and amino acid supplementation on performance and training adaptations during ten weeks of resistance training. J Strength Cond Res. 2006;20(3):643-53.

8. Allman BR, Morrissey MC, Kim JS, Panton LB, Contreras RJ, Hickner RC, et al. Lipolysis and Fat Oxidation Are Not Altered with Presleep Compared with Daytime Casein Protein Intake in Resistance-Trained Women. J Nutr. 2020;150(1):47-54.

9. Costa JV, Michel JM, Madzima TA. The Acute Effects of a Relative Dose of Pre-Sleep Protein on Recovery Following Evening Resistance Exercise in Active Young Men. Sports (Basel). 2021;9(4).

10. Trommelen J, van Loon LJ. Pre-Sleep Protein Ingestion to Improve the Skeletal Muscle Adaptive Response to Exercise Training. Nutrients. 2016;8(12).