Athletes at every level are inundated by messages citing the importance of refueling their muscles with protein powder. As a result, the amount of whey protein supplements has exploded in recent years.

Whey proteins vary greatly in quality and – consequently – price. But something that may surprise you is the speed at which different types of whey are digested by the body. Digestion speed is important because it dictates how quickly your body accesses whey protein’s valuable nutrients.

Here are the three different kinds of whey protein and reasons why some are digested quicker than others:

Slowest digestion – Whey protein concentrate

Whey protein concentrate’s purity varies anywhere from 25 to 89 percent and it can contain fat, lactose and other products. This type of protein is generally less expensive than others but is lower quality. “Due to the small amounts of fat and lactose that remain, your body digests whey concentrate more slowly than the other forms of whey,” wrote Richard Choueiri, an ACSM certified personal trainer with exercise science and nutritional science degrees from Rutgers University.

Faster digestion – Whey protein isolate

Whey protein isolate reaches a much higher purity than whey protein concentrate at 90-95 percent. It also largely filters out fat and lactose, which results in a quicker digestion rate.

Fastest digestion – Whey protein hydrolysate

Whey hydrolysate is the only protein that can be absorbed more quickly than isolate. “This type of protein is a result of the splitting of whey isolate into smaller chains of amino acids,” Choueiri wrote.

So, which type of whey protein is best for you? If you don’t want to spend very much money, then finding a whey concentrate that reaches higher purity like 70-80 percent isn’t a bad option. People who want best results and the purest protein should spend the few extra dollars to consume whey protein isolate or whey protein hydrolysate.