I have a daughter and a son who are regular consumer of protein shakes. Looks to like a very convenient way of getting one's daily dose of protein as absolutely no cooking and no mess for cleaning up is involved. Just shovel tablespoons of powder into a blender, add water and a bit of soy bean milk and whirl the mixture for a few seconds and presto, meal for the day is ready for consumption.
According to Wikipedia, whey protein is a by product in the manufacture of cheese from cow's milk. Whey is the liquid portion of curdled milk and whey protein are a collection of globular proteins that can be isolated from whey and typically comprises approximately 65% of beta-lactoglobulin, 25% of alpha-lactabumin and 8% of serum albumin. Whey protein is easily digestible, has the highest biological value of all the known proteins and also has disease-fighting abilities. Biological value (BV) is a measure of the proportion of absorbed protein from a food which becomes incorporated into the proteins of the organism's body.
When whey protein is processed to remove fat and lactose, what is left is called Whey Protein Isolates comprising 90% protein. As whey protein isolates are lactose free, they are suitable for consumption by those who have lactose intolerance.