Whey is a powdered food source. There is no upper threshold of how much protein you should get from shakes, but you should be sensible about balancing solid food with shakes. It’s best to think of protein powders as compliments to an already varied diet – supplemental. The one serious consideration is that when you are dieting, hunger will be your enemy at some point, so it's best to limit the calories you drink in favor of real food to help.