If milk proteins were siblings, casein would almost certainly suffer from little brother syndrome. Walk into any gym, and the only protein people seem talk about is whey. Walk down most supplement aisles, and nearly every protein tub you’ll see will contain whey. Skim the scientific literature, and almost every study you’ll read will focus on (you guessed it) whey. And there’s a good reason for that: Gram for gram, nothing beats whey when it comes to building muscle. Which begs the question: Should you even consider taking casein?
“The answer is yes, and the reason is simple,” says Nima Alamdari, Ph.D., Beachbody’s executive director of scientific affairs. “There are situations beyond the immediate post-workout period in which casein is a better choice for promoting muscle protein synthesis [AKA muscle growth].”
We’ll explore those situations in a bit. First, lets look at the differences between these two popular milk proteins.
Casein vs. Whey
As with any good discussion of sports nutrition, we must first turn to nursery rhymes. If you’re familiar with Little Miss Muffet, who sat on her tuffet, eating her curds and whey, then you’re familiar with whey and casein. The curds (i.e., the solid portion of Little Miss Muffet’s snack, also known as cottage cheese) are casein, which comprises about 80 percent of the protein in cow’s milk. Whey, the liquid, makes up the other 20 percent.
Like whey, casein is a complete protein, meaning that unlike most plant proteins, it contains all nine essential amino acids (i.e., those your body can’t produce on its own) in sufficient quantities to support bodily functions. Also like whey, there are several variants of casein available to consumers, including calcium caseinate, hydrolyzed casein, and micellar casein, which is the purest form, and generally regarded as the most effective. But that’s where the similarities between the two milk proteins end.
“Whey, which is acid soluble, is digested and absorbed quickly, which is why it’s commonly prescribed for post-workout,” says Francis Stephens, Ph.D., a Beachbody scientific advisor and an associate professor of metabolic and molecular physiology at the University of Nottingham, in England. “Casein, on the other hand, is insoluble, so it digests much more slowly.”
Cottage cheese provides a decent approximation of what happens to casein when it enters your body. Unlike whey proteins, which dissolve quickly in the acidic environment of the stomach, casein proteins gel together, forming clumps known as micelles. “That clumping is what slows its digestion,” says Alamdari. “And while that might seem like a disadvantage, there are certain situations in which a slow rate of digestion is exactly what you want.”
The Best Time to Take Casein
Sleep is one of those situations. “People often talk about the post-workout ‘window of opportunity,’ during which protein ingestion can have a more pronounced effect on protein synthesis,” says Alamdari, adding that there’s a second, even longer ‘window of opportunity’ that many people don’t know about or never consider. “That window occurs during sleep, and the best way to capitalize on it is to ingest a slow-digesting protein, like casein, within one hour of going to bed.”
Many key muscle-building processes occur while you’re in dreamland, including an increase in growth hormone. But one process that doesn’t normally occur efficiently during that time is protein synthesis, and this deficiency is largely due to a lack of available protein.
Unlike fat and glucose, protein is not stored in the body. As a result, you don’t have a stockpile you can tap into during periods of fasting, such as sleep. “When you ingest protein, your body breaks it down into amino acids, which circulate in the blood and are used for various purposes throughout the body, including building muscle,” explains Alamdari. The only way to maintain this circulating “pool” of aminos is by regularly eating protein, and since you don’t normally do that while you sleep, the pool runs dry, and remains depleted until you “break fast” the next morning.
“But if you consume a slow-digesting protein, like casein, before you go to sleep, you can turn this normally catabolic overnight period into an anabolic one,” says Stephens. Translation: Instead of breaking down muscle (or at least putting the brakes on its growth) while you slumber, you actively build it. And the effects can be dramatic, according to a recent study at the University of Maastricht, in the Netherlands. The scientists discovered that participants who combined daily resistance training with a pre-bed casein shake for 12 weeks gained 11 percent more muscle than those who did not.
How Much Casein Should You Take?
The recommendation for casein is the same as that for whey: 20 grams. That’s the amount of protein that researchers at McMaster University, in Canada, found to maximally stimulate protein synthesis in a study published in the American Journal of Clinical Nutrition. “That’s also why we established 20 grams as the optimal serving size for most people for Beachbody Performance Recharge,” says Alamdari. (If you’d like to customize your dose, shoot for .11g to .14g per pound of bodyweight.)
“It’s important to keep in mind, however, that specific protein timing doesn’t matter if you don’t consume adequate daily protein,” says Alamdari. The reason: You don’t just build muscle after a workout and while you sleep. It’s a continuous, 24-hour process. Shoot for .6g of protein per pound of bodyweight per day. And yes, your post-workout and pre-bed shakes count toward that goal.