Whey Protein Isolate (WPI) is one of the best protein sources, characterized by extremely fast absorption of amino acids. Therefore, it is an ideal choice for consumption after training. Special attention should be paid to the high content of branched-chain amino acids (BCAAs) and essential amino acids (EAAs), which are essential for effective muscle recovery and growth. Whey protein isolate stands out from other protein sources due to ultrafiltration. As a result of this process, the content of fats, carbohydrates, and lactose is significantly reduced, which increases the proportion of pure protein in the product. In addition, whey protein isolate, thanks to its lower lactose content, is also suitable for people with lactose intolerance.