What Casein Protein Powder Does

Build muscle ... overnight?

YOU'VE LIKELY HEARD about whey protein (the stuff is everywhere) and maybe even pea protein (the plant-based up-and-comer), but there's another protein that's popular among the fitness community: casein.

Casein shares more in common with whey than it does with peas, but casein is also distinctly different from both—and has unique benefits.

"There are two different types of protein in cow's, goat's and sheep's milk—casein and whey," says Kim Yawitz, R.D., a gym owner in St. Louis, MO.

"About 80 percent of the protein in cow's milk is casein, and about 20 percent of it is whey, according to a study in the Iranian Journal of Pharmaceutical Research," says Amy Gorin, M.S., R.D.N., an inclusive plant-based dietitian in Stamford, CT and owner of Plant Based with Amy. "Whey and casein are both complete proteins and are different in several ways. For one, whey protein is digested more quickly than casein protein."

Ahead, the scoop on all things casein protein.

To recap, casein is one of two major proteins found in dairy products. "It's also used to make protein supplements," says Yawitz, noting that such supplements come in two forms: micellar casein and casein hydrolysate. "Micellar casein is slow-digesting, while casein hydrolysate is predigested for faster absorption."

Because casein protein contains all the amino acids required by the human body, it's a complete protein, says Gorin. "It's also more slowly digestible than whey protein and is released into the body more slowly, which means that it keeps you fuller for longer periods of time."

Plus, as Gorin points out, "research has found casein to offer many health benefits, including potential cancer-fighting properties." Of course, more research is needed to verify these findings, but the possible health benefits of casein protein seem encouraging.

As you’ve likely gathered, dairy is the best source of casein protein. "Casein is mostly found in dairy products—milk, hard cheese, cottage cheese, and yogurt," says Yawitz. "There's no specific recommendation for how much casein men need in a day (and you won't find grams of casein listed on a food label, so it can be difficult to know exactly how much you’re getting from the diet)."

If you don't eat a ton of dairy, should you take a supplement? Probably not. "You don't necessarily need to use a casein supplement, especially if you get plenty of protein throughout the day," says Yawitz, sharing that a typical dose for men who choose to use casein supplements is 20 to 40 grams daily.

If you’re all about bulking up, casein protein may be particularly beneficial.

"Assuming you lift weights or perform other resistance exercises regularly, casein protein can help you build muscle and recover faster," says Yawitz. "Most importantly, casein supplements can help you get enough protein for muscle repair and growth."

As Yawitz highlights, studies suggest that daily protein intakes ranging from 0.73 to 1 gram per pound of body weight can help maximize resistance training-induced muscle growth. "And getting that much protein is often easier said than done, especially if your schedule is hectic or you tend to get full quickly when eating high-protein foods," she says.

Casein supplements typically contain around 25 grams of protein per scoop, says Yawitz, commenting that they are quite convenient to consume, making it one reason why they’re so popular with bodybuilders and other fitness enthusiasts.

"Even if you get enough protein throughout the day, there may be some added benefit to taking casein supplements (or eating casein-rich foods) before bed," adds Yawitz. "Going to bed with an empty stomach can increase the likelihood that your body will break down muscle proteins for energy and nutrients, making it more challenging to repair and build muscle. Casein takes several hours to digest and absorb, so taking it before bed could help spare muscle proteins, allowing your muscles to recover better and possibly even grow."

Yawitz points to one study where muscle protein synthesis was 22 percent greater in subjects who took a casein supplement before bed, compared to those who took a placebo.

Still, it's worth flagging that casein probably isn't the top choice if you’re looking for a post-workout protein supplement. "Whey protein is digested and absorbed much more quickly than casein, so your body can get straight to work repairing and building muscle," says Yawitz.

It may be obvious, but it bears stating: If you’ve been diagnosed with a milk allergy avoid casein rich-foods and supplements.

"I’m often asked about casein for those with lactose intolerance. With lactose intolerance, the sugar in milk is problematic rather than the casein or whey," elaborates Yawitz. "Most lactose-free dairy products still contain casein, so those are great options if you have a diagnosed intolerance," she continues, adding that casein powders can be tricky, as they sometimes contain trace amounts of lactose, so it's best to proceed with caution.

And another word for the wise: Always check supplements’ labels and look for products that undergo third-party testing—you can confirm this via an insignia on the product packaging—since the FDA doesn't regulate most nutritional supplements, which leaves a lot of room for inaccuracy on product and nutrition labels, says Yawitz. "Supplements that have undergone third-party testing are evaluated by an objective party to ensure that the labeling is accurate."

Perri is a New York City-born and -based writer; she holds a bachelor's in psychology from Columbia University and is also a culinary school graduate of the plant-based Natural Gourmet Institute, which is now the Natural Gourmet Center at the Institute of Culinary Education. Her work has appeared in the New York Post, Men's Journal, Rolling Stone, Oprah Daily, Insider.com, Architectural Digest, Southern Living, and more. She's probably seen Dave Matthews Band in your hometown, and she'll never turn down a bloody mary. Learn more at VeganWhenSober.com.

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