Could This Popular Protein Supplement Be the Secret to Restful Sleep?

Casein protein is a favorite supplement for athletes' muscle recovery, but health experts also praise its ability to help promote quality sleep.

A young woman makes a protein cocktail in the kitchen at home.
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No matter how it’s consumed, a high-protein diet is essential for anyone hoping to maintain good health. Protein is not just responsible for building muscle mass and making #gainz like Schwarzenegger — it also serves critical roles in the human body, like fostering communication between cells, tissues, and organs, regulating pH levels, and boosting your immune system by increasing antibodies.

Animal-, plant-, and even powder-based protein options all provide value, but there is one particular type of milk-derived protein that experts say may actually encourage more restful, high-quality sleep if taken right before bedtime. Enter casein, the high-calcium, slow-metabolizing supplement that has become a favorite of athletes and insiders.

What is casein?

“Casein, just like whey, are the two proteins found in milk,” explains Kristin G. Kelley, certified health coach of Inner Self Holistic Health. “When looking at cow’s milk, for example, casein makes up 80% of the milk protein and whey makes up the remaining 20%.”

“These animal proteins are pretty special, as they contain all nine essential amino acids we are required to obtain from our diets [to survive and thrive], since our bodies are incapable of producing them [on their own],” she says, adding that only a handful of plant sources like quinoa, buckwheat, hemp seeds, and spirulina are capable of providing the same full protein portfolio.

Casein is also full of beneficial nutrients like bone-strengthening calcium, as well as bioactive peptides that have been shown to lower blood pressure.

Though casein and whey come from the same source, they serve a few different functions and metabolize differently in the body.

“One big difference between casein and whey is that casein takes almost 10 times longer to digest than whey,” reveals Kelley. “This quick metabolization is why people tend to choose whey protein [to satiate] during a meal or right after a workout and why casein may be an attractive option overnight and when we go through a longer fasting period.”

The longer metabolization time of casein means that casein can potentially make you feel full longer and can work to repair and grow muscles over an extended period of time, which makes it even more suitable for consumption prior to sleeping when your body is (hopefully) stationary for eight hours.

How does casein protein help with sleep?

Aside from being a slowly digested protein that assists in muscle recovery and an overall feeling of “fullness,” casein may actually help people fall asleep quicker and stay asleep longer, according to some studies.

“Findings are fairly thin, but casein seems to improve individual perception of sleep,” says sleep specialist and neurologist Dr. Chris Winter. “Research subjects reported increased total sleep time and sleep efficiency, as well as decreased sleep latency — otherwise known as time it takes to fall asleep — and wake after sleep onset (WASO).”

“Actigraphy data showed significantly increased sleep efficiency (time asleep versus time in bed) after continuous use of casein for four weeks,” he says. Winter notes that sleep study findings showed similar trends, though not enough to be statistically significant.

One likely reason casein protein may be helpful to people in falling asleep is that it contains tryptophan, an amino acid that activates the relaxing neurotransmitter 5-HT, which is the precursor to sleep-inducing melatonin. Melatonin is a hormone your brain produces in response to darkness that ultimately regulates your body’s circadian rhythm to help it know when it’s time to fall asleep or wake up, so tryptophan — most famously found in turkey — is essentially an aid for the sleep aid.

While more research is necessary to draw more definitive conclusions, knocking back that casein protein shake before bed shouldn’t hurt unless it’s high in sugar or you already follow certain dietary restrictions.

“Since casein is a dairy product, those who are lactose intolerant or lactose averse should avoid casein and whey and consider vegan options such as soy or pea proteins,” advises Kelley. “Anyone who wants to engage in a vegan lifestyle should also avoid casein, as it is animal-derived.”

Which foods contain casein?

Casein is most readily available and marketed in powder form, with products that actually encourage nighttime use, but the act of chugging a heavy shake before bed can be quite off-putting, especially for picky eaters or those with a sensitive stomach.

As an alternative, because casein is derived from milk, it can be found in lighter dairy products, like cheeses and yogurts.

“Some of the most concentrated sources of casein are cottage cheese and Greek yogurt,” reveals Kelley. “For example, one cup of 2% milk has about 7-8 grams of protein while one cup of cottage cheese has about 27 grams of protein.”

Other high-casein sources include cream, butter, sour cream, and even ice cream, but it is important to keep in mind that any ingredient additions, especially those with sugar, may counter the sleepy effects of these foods in their purest form. It’s best to check with a nutritionist or registered dietician to confirm what makes the most sense and whether or not incorporating certain dairy products will counter any potential health benefits.

What to know about trying casein protein before bed

While casein shows promising signs of enhanced sleep quality, no supplement is a miracle worker.

“We are all unique and with anything, it’s important to remember results vary,” reminds Kelley. “It’s imperative that we learn to listen to our bodies when we try new things and honor what they tell us.”

But many people crave a late-night snack, and casein protein is proving that there is more than just comfort to warm milk before bed — the casein protein in dairy could very well bring on better sleep.

if you’re open to experimenting with a new and low-risk assistant for quality sleep (and let’s face it, a lot of chronically exhausted people are), it’s an option that will potentially yield some great benefits, particularly for those who are active and who eat a well-balanced diet.