Whey vs Casein Protein: What's the Difference?

By Mark Barroso

By: Mark Barroso, NSCA-CPT


Protein is made of amino acids, which increase protein synthesis and help prevent muscle breakdown. In other words, protein helps athletes recover from workouts without losing muscle mass.

When you lift weights or do cardio, your body burns through its stored carbs and fat first, then starts to break down protein (like that in your muscles) for energy.

If you want to build muscle, you need your body to build up more protein than it breaks down.


Whey protein is one of two proteins found in cow’s milk, the other being casein protein. When a coagulant or solid-making substance is added to milk, the casein, and whey separate.

“If the goal in the factory is whey production, the first thing they’ll do is spin milk so the fat is on the top then they get rid of the fat,” says Layne Norton, Ph.D. Nutritional Sciences, and owner of Biolayne.com. “Then, they add acid to the protein fraction that’s left over which precipitates the insoluble casein causing it to sink down. The whey concentrate fraction is soluble in acid and will be the clear liquid on top. If you evaporate the liquid and make it powder, you’re left with whey protein concentrate powder.” 

Essentially, the fat is removed from milk, then acid is added to the protein to separate it into concentrate and casein. Whey protein isolate is processed even more. 

“If you take whey concentrate through some type of filtration you can get whey protein isolate which is usually very low in fat, lactose, and carbohydrates,” adds Norton. “Whey isolate is usually better for people who have digestive issues with lactose.”


If you take the processing a step further, you can chop up the isolate whey peptides into shorter fractions creating whey hydrolysate.

“Whey hydrolysate has been theorized to absorb faster and be hypoallergenic so even people who have alpha and beta lactalbumin (the two major fractions in whey) sensitivity, won’t have an allergic reaction,” explains Norton. “The lactalbumin fractions gets chopped up so that person won’t have an allergic response. The hydrolysis process typically makes it taste a bit bitter.”

Hydrolysate is the most expensive of all proteins and typically don’t come in a variety of flavors.


Whey concentrate is less expensive than isolate and hydrolysate. Norton says there is one purported benefit of concentrate over isolate.

“I believe there are higher levels of glutathione in whey concentrate and it’s been proposed that there may be immune system benefits you’d get with concentrate that you wouldn’t get from an isolate,” says Norton. 

Cellucor’s COR-Performance Whey and Whey Sport Protein Powder contain a blend of isolate and concentrate. This provides the best of both worlds from a taste, health and macronutrient standpoint. Plus, a whey blend is more affordable than just an isolate. In fact, pure isolate is about 30% more expensive than concentrate, according to Norton.

“A good number of people can’t tolerate 100% whey protein concentrate and have at least some sensitivity to lactalbumin,” says Norton. “People may not have a straight-up allergy but are a bit sensitive and can tolerate a whey/isolate blend. If you’re using a blend of isolate and concentrate, the isolate brings the fat and carb content down. It makes the macros more friendly to the user.”


Casein protein is the fraction that’s left over after the acid is added during the processing of whey. 

“I’m not exactly sure of the next steps in terms of specifics, but they probably just purify it and make it a powder from there,” said Norton. “From a physiological perspective, your stomach is also very acidic. Whey is soluble in stomach acid and can be suspended in fluid whereas casein will precipitate and be a solid.”

Casein protein tends to move through the gastrointestinal tract more slowly. It tends to gel in the stomach and its release into the small intestine is very slow so you can get a sustained release of amino acids. Bodybuilders often take casein protein before they go to sleep so this “amino acid drip” occurs in bed.

Casein protein has a much thicker consistency compared to any type of whey so it requires more water to be palatable. That said some casein protein powders taste great and are just as thin as other whey blends.

Finding the casein that agrees with your digestive system will be key to unlocking those long-lasting muscle building benefits.  


I’m an NSCA-CPT, Spartan SGX Coach, and obstacle course racing athlete who has been lifting weights since age 16. My journey with protein supplements started at age 16 when I decided to build muscle and lift weights to get better at high school football.

Between ages 16-18, I didn’t really know the difference between isolate and concentrate. Admittedly, the focus for me wasn’t the macronutrients or “lean gains,” it was more about gains at all costs. Freshman year of high school I wrestled at 130 pounds and by the end of senior year, I was entering The College of New Jersey at 190 pounds. I never had a personal trainer or strength coach—all my lifting and nutrition was done on my own. 

A synchronous combination of a growth spurt, starting to lift weights, and drinking protein shakes, almost daily, attributed for 60 pounds of muscle gained in high school, half of which occurred in a little over a year. I would wake up, make a protein shake in a blender, then go to the weight room as my gym period.

Once college came around, it was time to try and get even bigger since I was fighting for playing time on TCNJ’s varsity football team. I experimented with weight gainers and more whey concentrate/isolate/hydrolysate blends but in the end, football practice would burn all the calories I was gaining.

In the offseason, I wasn’t doing too much to get better and football wound up not being for me after two years. I continued to lift weights and my protein knowledge increased after I started working for a major fitness magazine. Fast forward four years and I’ve tried pretty much every protein on the shelf.

These days, I fluctuate between 195-200 pounds and I mostly drink protein shakes in the morning as a “pre” breakfast. For example, if I have a 6am or 7am client, I’ll drink a protein shake and eat a banana, train the person, then make or buy breakfast.

I don’t have a favorite protein source per say and I often actually mix whey protein and plant-based protein in the same drink. I do enjoy flavored protein powder over unflavored, even if the unflavored is grass-fed. If it tastes like I’m drinking milk with no sugar, then it’s not fun for me. I grew up on drinking the shakes for their flavor not just what they can do. Cellucor’s COR-Performance Whey tastes amazing. I love chocolate so the molten chocolate meets my needs and the cookies and cream has actual cookie bits which is a huge plus in a shaker cup. 

Overall, I think I’ll always take protein powder after some hard weightlifting workouts and long runs. I just so happen to eat a decent amount of protein in my diet so I don’t need powder every day to maintain my frame. If I were to try to gain mass quickly, I’d increase my protein intake to at least 1-2 scoops every day for 4-8 weeks.

Protein supplements can make a big difference in a lifter’s physique if they are consistent with their dosages.

Looking for a Grass-Fed whey option? Try the new IsoPro Grass-Fed Native Whey!

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