No one on this planet gets indigestion when they start eating 10 cups of veggies and 4-8oz of meat in every meal coming from a diet high in refined carbs and processed meats (typical american diet).
Actually, Chris, I have to disagree with you there. Tombb seems to be right on this one.
Before I made a concerted effort to clean up my diet, my food intake was the "typical American diet" you're talking about here. Lots and lots of starchy stuff, insane amounts of sugar, and lots and lots of processed meats. When I was used to that diet, I wasn't used to eating veggies - other than maybe highly processed potatoes - at all. Eating just 1 cup of vegetables would make me sick. As in, I'd have nasty stomach cramps (and other results) for the entire next day.
At this point, I try to make sure I have a couple cups of vegetables and a
good source of protein with each of my meals. My stomach is used to that now, so there aren't any weird digestive issues anymore when I eat vegetables, even in large quantities. However, my stomach is no longer used to the stuff I used to eat, so now THAT stuff makes me feel icky and nauseous instead.
Basically, it seems to be a factor of what you're used to. If your diet is fairly homogeneous for long enough, and then you eat a large enough quantity of something your stomach doesn't know how to handle (or at least isn't prepared to handle past a certain quantity), you're going to experience results of one sort or another. The magnitude of the response will, no doubt, vary from person to person, but the same thing will happen no matter WHAT it is that you're used to or not used to.
Me, I'd rather have my body used to eating healthy stuff and unprepared to handle "crap" than the other way around. If nothing else, it's a good deterrent.