Where it comes from: Casein protein powder is simply the dehydrated, supplemental form of casein. Caseins are phosphorus-containing proteins and make up 80 percent of the protein in cow's milk (the other 20 percent of protein is made up of whey proteins). "So even though cow's milk contains both casein and whey, casein is often called milk protein," explains Sarah Currie, RD and personal trainer for New York City-based Physical Equilibrium LLC. Casein as a powder is used to make workout protein shakes and comes in a variety of flavors.
What it'll do for you: "There aren't necessarily benefits of casein protein powder," cautions Currie, "especially since most people's protein needs can be met with food alone." However, some people think casein is a superior protein supplement and a handful of studies could sway the jury:
- Helps build muscle mass
In a recent study, 17 men drank two protein shakes a day—either right before and after their workout sessions or at least five hours after their training. When measured 10 weeks into the study, the men who flanked their workouts with shakes built almost twice as muscle than the other men. Another study, this time performed at Baylor University, found that men who drank a casein protein shake (blended with whey) for 10 weeks gained significantly more muscle mass than the subjects who consumed a whey protein shake without casein.
- Speeds up muscle recovery time
Casein powder moves through the digestive tract slower than whey protein and can take up to seven hours to fully digest. Since the majority of muscle repair and regrowth happens when the body is asleep—and casein powder has such a long digestion time—it's ideal to take the powder before bed and is known as a "night time" protein. This way, the body gets a slow release of protein throughout the night and can aid in muscle recovery.
Suggested intake: "Rarely is protein supplementation necessary in a healthy diet," notes Currie. "Amino acids supplied by protein supplements offer no special benefits beyond what food can supply." Currie insists that eating extra protein to promote muscle growth is a myth: "For muscles to grow, they must be stimulated physically and receive adequate protein, not excessive. Any macronutrient (protein, fat, carbohydrate) in excess will be stored as fat."
Currie (along with many other experts we've talked to) recommends getting your casein dosage by eating food. It's found in milk and any foods which contain milk such as butter, cheese, ice cream and yogurt.
"When people have a hard time meeting their protein needs with food (the critically ill, strict vegetarians, body builders, pregnant women in their third trimester, etc) then a protein supplement may be necessary, but that's usually on a case-by-case basis," says Currie. If you fall in that category—or want to take casein protein powder supplements anyway—make sure you're buying a label from a reputable company. Assuming the supplement is legit, casein protein powder shouldn't be different than how it's found in its natural form in milk.
Associated risks/scrutiny: Over-consumption of casein and proteins can strain kidney function and lead to dehydration, slowed digestion and fat storage—the body will convert excess protein to fat if it can't use it.
Casein allergies are common but are not to be confused with a lactose intolerance. Minor casein allergy symptoms include rashes, stomach cramps, bloating, hives and stomach pains.