Ounce for ounce, whey protein has the most natural occurring branch chain amino acids than any other food. So a little goes a long way.
Whey protein comes in two different forms. Whey protein isolate and whey protein concentrate. The main difference between the 2 is that the
isolate form is more pure. Isolate contains 90-98% protein whereas concentrate is 70-85% protein. Most companies combine the two forms. Whey concentrates tend to be higher in fat and lactose content. So if you have a sensitivity/intolerance to lactose, you're better off finding a whey protein isolate or avoiding it all together. Finding a whey protein isolate with less that 0.1g of lactose per tablespoon has been found to be quite tolerable for these individuals.