Only whey protein isolate can ensure that one gets enough protein while still providing the great taste needed to make the supplement edible. There are lots of alternatives that fit the classic pattern of health food that tastes blasé at best and downright horrible at worst. Sticking to milk based examples is the only way to ensure that one can actually enjoy the flavor of a protein supplement.
That's large because milk can make just about anything taste good, but also because it contains the most valuable proteins in terms of nutritional value of any naturally occurring food – its first purpose, after all, is to nourish young and growing bodies. When it's refined to make whey protein isolate, the resulting supplement is a very pure source of these precious proteins, so that the benefits are available in high quantities.
That makes it a lot easier to mix them in effect with whatever one wants to make more nutritious. They blend in well with any food that can take milk, dramatically increasing the nutritional value and, if the flavor options are well coordinated, transforming that meal into an exquisite treat. However, whey protein isolate is most commonly noted for how effectively it mixes with water or milk to make an outstanding protein shake.
As a result, it's easy to understand why whey protein isolate is such a popular option for people trying to improve their diets. It provides one of the most vital ingredients of daily nutrition while still enjoying an agreeable taste. That's something worthy of a lot more respect than people normally afford for health food.