Whey protein concentrate is a byproduct of cheese manufacturing, and it is the liquid that is left over after the milk has been processed. WPC consists of approximately 80% protein, with minimal, but slightly higher levels of carbohydrates and fats than the other whey protein, whey protein isolate (WPI). WPC also has more lactose, this is why those who have sensitivities to lactose often choose WPI as their protein source. WPC has a full amino acid profile, making it one of the best protein sources on the planet.