When it comes to protein powders, whey gets all the glory. But it’s not the only dairy protein that offers benefits. Casein is just as helpful at building muscle and improving strength. In fact, its specific amino acid profile and slow digestion make it a good addition to any muscle-building diet plan.

Casein vs. Whey

Casein and whey are the two primary proteins found in cow’s milk. A single glass is usually comprised of about 80 percent casein and 20 percent whey. If you’re a visual person, when milk coagulates, casein is the curd, while whey is the liquid.

One of the primary differences between casein and whey is rate of digestion. Whey digests quickly, while casein takes longer. This is one of the primary reasons so many in the athletic world prefer whey protein. It gets to the muscles faster. However, while both are a rich source of all the essential amino acids, which are the amino acids your body must get from food, the body is better at breaking down and absorbing the protein and amino acids from casein than whey. That means casein provides more overall protein to your muscles.

The Benefits of Slow Digestion

While whey protein may be preferred for its fast-acting capabilities after a heavy muscle-building workout, what about the muscle building that happens later? Or when you go too long without eating, and your body uses your own muscle for fuel? As a slower digesting protein, often referred to as an anti-catabolic protein, casein may serve to help both of these scenarios. A 2001 study published in The American Journal of Physiology, Endocrinology and Metabolism found that slower-digesting casein increases long-term post-meal amino acid circulation, which may help promote anabolism of muscle well after you’ve eaten, and prevent catabolism. These protein-building benefits may last up to at least 7 hours, according to researchers.

Forms of Casein

Casein comes in two forms: casein hydrolysate and micellar casein. The hydrolysate form is predigested and absorbs quickly, and is the main protein source in hypoallergenic infant formulas. Micellar casein digests more slowly and is rich in calcium and phosphorus. When looking to supplement with casein powder, you want to look for this type of casein. A good choice includes Ascent Native Fuel ™ Micellar Casein. One rounded scoop of this supplement contains 25 grams of slow-absorbing casein protein.

Does It Work

Like whey, there’s a lot of research that supports the benefits of supplementing with casein. A 2013 study published in the Journal of Sports Medicine and Science compared the effects of casein versus whey supplements taken before and after exercise on body composition in a group of college-age female athletes. The women in the study taking the casein protein powder increased lean body mass, decreased fat mass and improved physical performance. It’s important to note that there was no significant difference between the casein and whey protein group, meaning they were both equally beneficial.

An earlier study published in the Annals of Nutrition and Metabolism comparing the differences in the two milk proteins on body composition in a group of men engaging in regular resistance training found that casein takers lost more fat than the whey takers. Both groups increased muscle mass.

A Word About Glutamine

One thing that separates casein from whey is glutamine. Glutamine is known as a semi-essential amino acid, which means technically your body is able to make it on its own, except under certain circumstances, including exercise related-stress. Low levels of glutamine affect immune health, and for the athlete or anyone involved in regular exercise, may impair performance (or your ability to finish that spin class). Casein, unlike whey, is a natural source of this amino acid. Taking a casein supplement after a workout may help replenish glutamine stores to improve immune health.

Adding Casein to Your Workout Plan


While the post-workout meal may be one of the most important meals, it may not be the best time to take your casein supplement. Unless, of course, it’s a glass of milk or a casein and whey mixed protein supplement. To get the most benefits, consider taking casein before bed to help your body build and repair muscle as you sleep. If you’re not into supplements, milk, along with cottage cheese and yogurt, can help you get more casein in your diet. As a source of protein, and possibly carbs and fat, whether in supplement or food form, casein needs to be included as part of your overall macro count.

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