http://www.mindandmuscle.net/articles/colby_vorland/probiotics Good article. Explains why some people have problems digesting even simple things like a scoop or two of protein. I use a multi-enzyme from vitamin shoppe that's around $6 a bottle and worth 100 times that. If you drink a lot of shakes, its good to take digestive enzymes at the same time too. You're body will not respond to digest and use the protein from a shake the same way it does from whole food. Yes you have the benefit of a liquid meal, but bloating and GI distress from shakes is common in people who otherwise have no digestive problems. Using digestive enzymes will mimick the same process your body completes when releasing enzymes to break down a whole food meal...