Here's a pretty complete answer from my in-house supplement expert, Rick Mull. He is a trainer, moto guy and all around cool dude at my personal training studio in Austin, TX called Pinnacle Elite Fitness:
Here is how it works. Protein is broken down into their purest forms, amino acids. The most concentrated amino in the body is L-Glutamine, which make up some 60% of muscle. Hardcore athletes will take this pure form of amino to help prevent muscle breakdown. While helpful, this is not necessary for the average “athlete”. Beyond aminos, you have protein in various forms including milk, eggs, chicken, whey(which come from dairy products, etc. They are all rated with a BV or biological value which is a rating of how much of the protein is actually converted to muscle. We used to think eggs whites were the gold standard, so we gave them a grade of 100. Milk products are in the 80’s, poultry is in the 60’s. Then science came along and it was discovered that whey was actually higher than eggs at 109. Then, before they could break it down much further, they mixed some other forms of protein like milk and egg back in and called this a concentrate, with a BV of 129. At around the same time, the white coats figured out how to break down the whey into the smallest, isolated molecule usable by the body. Whey isolate averages around 159. Id this important when it comes to muscle breakdown…absolutely. What it means is that a whey isolate is almost twice as likely to be converted to muscle as a piece of chicken. Is this healthy all of the time, not sure. Is it costly, yes. If you’re having trouble meeting your protein need through 5 squares, than I would recommend a protein shake. Isolates can be found fairly cheap these days so if you can find one that meets your budget, get it. If not, go with a concentrate. I myself use an isolate made by the Nutrition Depot. It’s their own in-house product so they make it cheaper than the rest. It runs about $48 for a 4lb can which is $12 per pound. That’s the best you can do for the money. Hope this helps.