Casein vs. Whey: Which Is Better For You?

Whey protein is one of the major parts of cow’s milk, explains Donald Layman, Ph.D., professor emeritus in the department of food science and human nutrition at the University of Illinois at Urbana-Champaign. “It [whey protein] makes up about 20% [of cow’s milk],” he adds.

Whey protein is naturally found in dairy products like milk, yogurt or cottage cheese. In fact, during cheesemaking, whey protein is found in the watery byproduct that can be dried and turned into whey protein powder.

“Some cheeses have residual amounts of whey in them while other cheeses have little to no whey. Cottage cheese and ricotta contain some whey protein,” explains Marie Spano, registered dietitian nutritionist and Dymatize sports nutrition consultant based in the Atlanta area. Hard cheeses such as Parmesan contain virtually no whey protein, she notes.

Whey protein is ideal for supplements because it’s easily extracted from milk in very pure forms, has a clean taste, mixes easily in water, has very high protein quality and is rapidly digested and absorbed in the intestinal tract, says Dr. Layman.

The two most common forms of whey protein are whey protein isolate and whey protein concentrate, adds Tavis Piattoly, registered dietitian nutritionist and co-founder of My Sports Dietitian based in the greater New Orleans region.

“Whey protein isolate contains a little bit more protein (around 90% protein) where whey protein concentrate—after manufacturing into powder—retains a little more carbohydrate and fat while providing 80% protein by weight,” he clarifies.

Whey protein powder is also used as an ingredient in the food industry in a variety of foods, from baked goods to ice creams, to snack bars and much more, suggests Douglas Kalman, Ph.D., co-founder of The International Society of Sports Nutrition and registered dietitian nutritionist at Nova Southeastern University in Fort Lauderdale, Florida.

Benefits of Whey Protein

“Whey protein is especially high in the amino acid leucine, which research has identified as a unique dietary signal to initiate muscle protein synthesis [the process of producing new muscle protein],” notes Dr. Layman.

Whey protein contains 11% to 12% leucine, while casein contains about 9%, eggs 9%, soy 8%, wheat 6.8% and quinoa 6%, he explains. Muscle protein synthesis requires about 3-4 grams of leucine to stimulate the process, so if a scoop of whey has about 24 grams of protein, that would provide about 3 grams of leucine to get muscle building started.

Because of this high leucine content and quicker digestion than some other protein options, 100% whey protein is frequently recommended by sports dietitians, adds Lauren Link, registered dietitian nutritionist, assistant athletics director for sports nutrition at Purdue University Athletics and vice president of The Collegiate and Professional Sports Dietitians Association.

In fact, some studies suggest that whey protein can stimulate muscle protein synthesis to a greater degree than other proteins such as casein and soy.

To maximize the benefits of whey protein on muscle strength and recovery, experts have moved away from the belief that people need to consume protein within 30 minutes after a workout to speed the recovery process, explains Piattoly.

“New evidence suggests timing may not matter if you consume protein before or after a workout as long as you’re meeting your daily protein requirements for the entire day,” he notes.

Whey protein may also be useful for supporting metabolic health and weight management, suggests Dr. Kalman. Some of its weight management benefits, according to Dr. Kalman and Stuart Phillips, Ph.D., a professor at McMaster University in Ontario, Canada, include:

• Weight loss: Several studies have found that when whey protein is used as part of a reduced calorie diet, it improves the response for weight loss, while also helping to preserve lean body mass.
• Increase feelings of fullness: Whey protein intake has also been validated as a strategy to blunt or reduce appetite in the short and longer durations.
• Markers of metabolic health: Whey protein also appears to positively impact fasting lipids (i.e., cholesterol), along with a positive impact on insulin. Some researchers have found that whey protein may lower blood pressure, but increasing dietary protein overall seems to lower blood pressure, not just whey.

Whey protein also contains bioactive peptides such as β-lactoglobulin and α-lactalbumin.

“These are proteins that may improve your immune system and may also provide antioxidant effects,” adds Piattoly.

Precautions Around Whey Protein

Whey protein is safe and should not cause side effects for the majority of individuals.

“Whey has been used in supplements for over 20 years with no adverse effects observed at any age,” explains Dr. Layman.

But for those who may be sensitive to dairy, ingesting whey protein may lead to bloating, diarrhea, stomach pain and nausea, adds Piattoly.

Whey protein isolate may have a lower lactose content, but usually comes with a higher price point due to having a higher purity rate, he continues.

People who are allergic to dairy should not use whey protein.

Individuals who live with kidney disease or kidney failure may need to limit the amount and frequency of protein, including whey, they consume—depending on their doctor’s recommendations.

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“Casein is the main protein in milk; cow’s milk is 80% casein,” notes Dr. Kalman.

Casein protein is found naturally in dairy foods like cottage cheese or yogurt, but can also be used as a dietary supplement, he adds.

Casein doesn’t mix well with water or acid, such as that found in the stomach.

“It [casein] forms—along with fat—clumps [curds] that are slow to exit the stomach and digest,” says Dr. Phillips. Because of this, casein is commonly referred to as a “slow digesting” protein.

The gel-like substance that forms in the stomach when casein protein is digested is why it takes the body twice as long to break it down compared to whey protein, adds Piattoly.

Benefits of Casein Protein

For the most part, experts point to casein protein having similar health benefits to whey protein. For example, casein can influence muscle gains and body composition in the same way whey protein does, explains Dr. Kalman.

A small 2023 study fed 36 healthy young men either 45 grams of casein protein, 45 grams of whey protein or no protein supplement 30 minutes before sleep after doing some endurance activity. Both proteins supported overnight muscle building and recovery^[1]Trommelen J, et al. Pre-sleep protein ingestion increases mitochondrial protein synthesis rates during overnight recovery from endurance exercise: a randomized controlled trial. Sports Med. 2023;53(7):1445-1455. .

Research suggests that both whey and casein proteins enhance feelings of fullness, but it isn’t entirely clear if one is better for weight loss given there are few studies comparing the two proteins to each other, explains Spano.

A 2020 review suggests that casein may lead to a long-term feeling of fullness over one to two hours, while whey has a short term effect on fullness after 20–30 minutes^[2]Kondrashina A, Brodkorb A, Giblin L. Dairy-derived peptides for satiety. Journal of Functional Foods. 2020;103801. .

There is also some thought that casein protein might help with sleep, notes Dr. Phillips.

A recent review assessing the effects of dairy products on sleep quality, including casein peptides like α-s1 casein tryptic hydrolysate, suggests there is preliminary but limited research in support of this idea and additional longer-term studies are needed^[3]St-Onge MP, Zuraikat FM, Neilson M. Exploring the role of dairy products in sleep quality: from population studies to mechanistic evaluations. Adv Nutr. 2023;14(2):283-294. .

Other bioactive peptides in casein, including β-casein, C12 peptide and lactotripeptides, have been shown to benefit the digestive, immune, and cardiovascular system, suggests Piattoly^[4]Auestad N, Layman DK. Dairy bioactive proteins and peptides: a narrative review. Nutr Rev. 2021;79(Suppl 2):36-47. ^[5]Sun S, et al. Effects of casein phosphopeptides on calcium absorption and metabolism bioactivity in vitro and in vivo. Food Funct. 2018;9(10):5220-5229. ^[6]Townsend R, McFadden CB, Ford V, et alCadee JA. A randomized, double-blind, placebo-controlled trial of casein protein hydrolyste (C12 peptide) in human essential hypertension. Am J Hepertens. 2004;17(11 Pt 1):1056-8. ^[7]Fekete ÁA, Givens DI, Lovegrove JA. Casein-derived lactotripeptides reduce systolic and diastolic blood pressure in a meta-analysis of randomised clinical trials. Nutrients. 2015;7(1):659-81. .

Because casein takes longer to absorb, digest and metabolize than whey protein does, it has been mostly promoted as a protein you consume at nighttime, adds Dr. Kalman.

“The slower digestion can help promote satiety and potentially replace less nutrient-dense snacks, while also providing a slow, steady release of amino acids into the bloodstream during the night,” notes Link. She explains that your body is still hard at work overnight after exercising, rebuilding and recovering.

However, researchers have found that the timing of casein protein, either day or night, does not seem to make a big difference for enhancing the effects of exercise, or benefiting muscle strength and size, notes Dr. Kalman.

Regardless, any protein, whether it be from whey or casein, will help before bed if you haven’t met your total daily protein needs, suggests Spano.

Precautions Around Casein Protein

“There are no known unique contraindications to consuming casein protein,” notes Spano.

However, as with any dairy product, people with sensitivities or intolerance to lactose, or a milk allergy, should use caution or avoid casein protein altogether.

“In addition, a variety of casein products may contain soy as an additive ingredient so those with soy allergies may want to take precautions,” notes Piattoly.

What’s most important is choosing a product that your body can tolerate well based on the nutritional and ingredient profile of the product, he adds.

Here’s an at-a-glance look at some of the similarities and differences between whey and casein protein, from experts.

	WHEY PROTEIN	CASEIN PROTEIN
Made From	Cow’s milk	Cow’s milk
Forms Consumed	Naturally found in all dairy foods Available in supplement form	Naturally found in all dairy foods Available in supplement form, but not as commonly used as whey
Calories Per Serving	Will depend on food or supplement	Will depend on food or supplement
Protein Per Serving	Will depend on food or supplement	Will depend on food or supplement
Cost	Typically more expensive than casein	Typically cheaper than whey
Digestion and Absorption Rate	Fast	Slow
Timing	Anytime, although commonly used for post-workout routines	Anytime, although commonly used for nighttime routines
Mixability (supplement form)	Mixes well with water	Does not mix well with water, thick texture and consistency
High Quality Protein	Yes	Yes
Health Benefit	Generally similar to casein protein. Research points to slight advantage for: • Muscle building	Generally similar to whey protein. Research points to slight advantage for: • Sleep
Who It Might Be Best For	Depends on personal health goals and lifestyle routine	Depends on personal health goals and lifestyle routine
Who Should Limit or Avoid It	People with lactose intolerance, sensitivity or milk allergy	People with lactose intolerance, sensitivity or milk allergy

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“Overall, both proteins are considered high quality,” says Dr. Layman. Piattoly adds that one is not superior to the other when it comes to optimizing health or results in your training program.

That said, determining which may be better for you could depend on the exact health goal you’re trying to accomplish and your lifestyle regiment.

For example, if your goal is to create a convenient, high quality, low calorie, good tasting protein shake, whey is by far the best choice, explains Dr. Layman.

If you are someone who uses protein powder to cook, casein would be great to use to make a high protein pudding, pancakes, or ice cream due to its ability to increase texture and thicken, notes Piattoly.

If you prefer to get your protein from whole food sources, both proteins are found naturally in dairy foods like milk, yogurt or cottage cheese that can keep you satiated for a longer period of time, help build muscle and enhance fat loss, adds Spano.

Many of the ready to drink protein beverages may actually have a combination of whey and casein, explains Dr. Kalman.

He adds that in the long run, it’s the consistency of overall protein intake that matters more than the dietary source for health benefits.

Eating a higher protein diet, at least 1.2 grams of protein per kilogram of bodyweight per day, can help preserve and build muscle, explains Spano.

To answer the question of which is better for you, it seems that consuming a combination of both whey and casein protein in a way that meets your personal taste, budgetary or health needs might be the answer.