There are different types of whey protein available, namely whey protein isolate (WPI), whey protein concentrate (WPC), and casein protein.

“Whey protein isolate is the purest form of protein on a gram-per-gram basis and will be at least 90% pure protein,” says Michael Twyman, MD, board-certified cardiologist at Apollo Cardiology based in Missouri. “WPI is produced by sending milk through a series of filters. The filters will strip out lactose and milk sugar as well as fat. WPI is generally better for those who are lactose intolerant or for people who get gastrointestinal problems from WPC.”

WPI is typically more expensive than WPC due to its purity and reduced fat, sugar, and carbohydrates. “WPC is produced similarly to WPI but the milk will be sent through fewer filters,” says Twyman. “WPC is good for most of the population that can tolerate lactose. Since it has more fat, it will contain certain bioactive peptides3 that can elicit some positive health benefits, Twyman adds.

During the whey manufacturing process, milk is spun then acid is added, which causes the soluble (dissolvable) portion (the WPC) to rise to the top. This WPC is then broken down into more peptides to form WPI.

The insoluble (less dissolvable in acid) casein protein will sink to the bottom during this process. Casein can also be consumed as a protein powder. It has a thicker consistency compared to WPC and WPI, so casein products typically require more water to go down smoothly. Casein doesn’t get digested as quickly as other forms of protein, so those looking to support muscle growth usually take it before sleeping to get amino acids as they recover. There are two types of beta-casein: A1 and A2. 

Though less common, you can also find whey protein hydrolysate, which is formed when WPI is broken down even more into more peptides so that it can be absorbed even faster. The difference between hydrolyzed whey protein and WPI is small, except the hydrolyzed will taste the most bitter of all proteins.