At the bottom of page 240 of "How to Brew", in his discussion on the two unfermentables in beer that contribute to body, namely unfermentable sugars and proteins, Palmer mentions that dextrins (carbohydrates that are long chain sugars) are suspected by some brewers to be the leading cause of beer farts.
It makes sense to me that mashing lower to create a more fermentable wort could solve the problem, or is worth trying, so that the beer's sugars are broken down in your stomach rather than in your intestines.