Here's an excerpt from the article:
The theory is that many people with IBS have trouble absorbing certain carbohydrates in their small intestines. Large molecules of those foods travel to the colon, where they are attacked by bacteria and ferment, creating the telltale IBS symptoms of gas, bloating, constipation or diarrhea.
A long list of foods—including dairy products, some fruits and vegetables, wheat, rye, corn syrup and artificial sweeteners—can potentially create such problems in susceptible people. Collectively, they're known as Fodmaps, an acronym that for stands for Fermentable Oligosaccharides, Disaccharides, Monosaccharides and Polyols.
The general theories behind this aren't anything new. In fact, they are very similar to the Specific Carbohydrate Diet in some ways. But if you look at what's "legal" vs. "illegal", there are some serious contradictions between the diets. I suppose that's not necessarily surprising, though, as IBS and IBD are different. But just interesting that one diet doesn't address both. I wonder if that hints to the cause at all?
At any rate, here's the graphic from the WSJ article that covers some of the low and high FODMAP foods:
