If you're interested in the concept, you might want to look into Natural Hygiene, which is a way of eating and living that promotes health (including fasting, nude sunbathing, and colonics, I believe). It's been around for a long time, at least since the 50's. There are charts available that show which food groups supposedly combine for best digestion (they differentiate between differnt types of vegetables, for example). I'm not "into" Natural Hygiene, but when I worked in a food co-op in the 70's, I read alot about all differnt kinds of natural ways of eating.
Several eating programs promote food combining "food for life" and Susanne Sommers Sommersize and two I know of (I think food for life would be more credible).
Of course, humans didn't evolve eating proteins separate from starches, etc., so there's really no need to eat that way. I'd wonder if doing so over the long run would make you less able to digest mixed meals?