Enzyme deficiencies
When your intestines lack enzymes to metabolize specific foods like milk or grains or beans, the food remains undigested, so you start feeding your intestines’ ravenous bacteria. The result: lots of intestinal dilation and more gas than a Hummer fuel tank. The most common of these is lactose intolerance (the lack of GI agreement with dairy products), and a close second is an allergy to the protein gluten from wheat (and rye and barley; nutritional good guys). As an example, when you lack the enzyme lactase, the sugar lactose in the milk reaching your intestine is not metabolized, so it’s presented to your intestinal bacteria, which metabolize the lactose in your intestines, producing a lot of gas.