When it comes to protein, whey rules the marketplace, and with good reason: It’s a powerful, well-researched and proven muscle-building nutrient. But if you’re a smart bodybuilder looking for every nutritional edge you can get, it shouldn’t be your only protein source.
Enter casein. Like whey, it’s derived from milk, and it’s a “complete” protein, meaning it contains all the essential amino acids. That makes it key for athletes engaged in resistance training, an endeavor that essentially breaks down muscle tissue — the amino acids serve as the building blocks to reconstruct that muscle during periods of rest and recovery.
Casein, again like whey (as well as soy and egg proteins), is effective in promoting positive protein balance in the body, and studies support its use before, during and after exercise for building mass and improving performance. Here’s more on this underrated supplement.
Steady as She Goes
One of casein’s key attributes is that it is digested slowly, compared to the more popular milk protein, whey. Researchers know this because the two proteins have different effects in the body after they’re ingested — namely, whey causes a quick spike in amino-acid concentrations in the blood, while casein produces an extended plateau.
Biologically, all protein is broken down into composite amino acids during digestion. Researchers can measure these amino acids using metabolic tracers, which are used to pinpoint specific aminos, like leucine or phenylalanine. It’s the unique properties of the different proteins that determine how they’re digested.
“Because of the properties of the casein, when it hits your gut, it curdles,” explains Kevin Tipton, Ph.D., a senior lecturer in the School of Sport and Exercise Sciences at the University of Birmingham in England. “In digestion, when a protein hits the stomach, it starts hydrolyzing the bonds of the amino acids in the polypeptide chain of the protein. [Casein] slows that down by causing the curdling, where the protein folds up on itself, so the amino acids come off more slowly.”
Not only does casein differ from whey during digestion, but also different forms of casein are digested differently. Micellar casein, calcium caseinate and sodium caseinate are “intact” casein proteins, and therefore digest gradually. Comparatively, hydrolyzed casein (aka casein hydrolysate) is processed to make it easier to digest. This was illustrated in the July 2009 American Journal of Clinical Nutrition. Researchers compared intact casein to casein hydrolysate and found that the hydrolyzed protein speeds up digestion, improves amino-acid availability, and increases the rate dietary amino acids are incorporated into skeletal muscle protein.
Preworkout Protein Boost
Despite the digestive differences between proteins, it’s accepted that protein itself is key if the goal is bulking up. Taking casein as part of a preworkout regimen has proved to improve muscle protein synthesis, a measure researchers use to estimate the rate of muscle growth.
“If [muscle protein synthesis] is higher, that means you’re building muscle faster,” Tipton explains. “Let’s say there are two conditions that we’re looking at, like casein versus another protein after exercise. Then we can compare the rates of synthesis, and the one with the higher rate, we interpret that to mean you’ll build muscle faster.”
Taking a protein supplement one hour before, as well as one hour after, training was shown to improve muscle protein synthesis in a 2007 issue of Amino Acids. For the study, researchers had 19 men participate in a 10-week resistance-training program and take either a protein supplement with 14 grams of combined casein and whey plus 6 grams of amino acids or a placebo on exercise days. During the study period, the guys taking the supplement gained more total body mass, fat-free mass, thigh mass and muscle strength than the men who took the placebo.
Fueling up before exercise has its obvious advantages, but using protein supplements during exercise has rewards of its own. In fact, adding a protein-carb supplement midworkout was shown to promote muscle protein synthesis in research published in the November 2008 Journal of Nutrition. The study showed that taking 0.15 grams of hydrolyzed casein per kilogram of bodyweight and an equal amount of carbs each hour during a two-hour training session, and then 30 and 90 minutes after exercise, increased whole-body protein synthesis by 40 percent in the three hours immediately postworkout.
Taking casein hydrolysate midworkout also may improve endurance, according to a report in the April 2009 International Journal of Sport Nutrition and Exercise Metabolism. The study of 13 male cyclists showed that the guys who took 200 milliliters of a carb-protein drink every 5 kilometers on a 20-kilometer course had better performance toward the end of the race than the cyclists who had a carb-only drink. The cyclists also took 500 milliliters of the drinks immediately after the race, which the researchers said helped prevent muscle soreness after exercise.
Refueling after a workout is a notably high priority in sports, particularly for boosting muscle mass. In fact, researchers reporting in a 2007 issue of Sports Medicine noted that muscle growth requires an après-exercise meal and that protein specifically is paramount for promoting a positive protein balance.
The type of protein may not actually make that big of a difference, according to a head-to-head comparison of casein and whey that Tipton and his colleagues published in the December 2004 Medicine & Science in Sports & Exercise. In their study, groups of healthy volunteers took 20 grams of casein, whey or a placebo one hour after doing leg-extension exercises. In looking at various measurements, the researchers found that both proteins promoted positive net amino-acid balance, although they didn’t do it exactly the same way. Despite the differences, the researchers concluded that casein and whey resulted in net muscle protein synthesis.
Another study showed that taking a daily dose of 70 grams of protein (82 percent casein) split into two portions at different times in the day helps enhance the benefits of resistance training. The study, which appeared in the June 2009 issue of Nutrition Research, involved a group of young men who participated in a 16-week training program. For the first eight weeks, they took 35 grams of protein in the morning and another 35 grams immediately before an afternoon training session. For the second eight weeks, they took 35 grams of protein in the morning and another 35 grams in the evening five hours after exercising. Although the guys only gained mass in the second half of the study, they got notably stronger during both regimens.
The Time Is Now
The research shows that taking casein before, during and after exercise — or anytime, really — effectively supports muscle protein synthesis and also boosts endurance and strength gains. In many cases, timing is everything, but in the case of casein, the only thing that seems to matter is actually taking it.