Foods that cause the most gas include beans, cheese and whole grains. Additionally, vegetables such as Brussels sprouts and broccoli, and fruits such as apples and prunes cause gas. Processed foods that contain a variety of ingredients also cause gas.
Beans commonly cause gas because they contain raffinose, a complex sugar that is hard to digest. When raffinose passes into the large intestine, it is broken down by bacteria causing the production of hydrogen, methane and carbon dioxide gas. Whole grains contain raffinose in addition to fiber and starch that must also be broken down by intestinal bacteria. Other gas-causing foods that contain raffinose include vegetables such as cabbage, asparagus and cauliflower.
Cheese contains the simple sugar lactose. Lactose is difficult to digest if the body does not produce the enzyme lactase. Lactose intolerance is caused by a deficiency in lactase and commonly results in gas production. Most dairy foods contain lactose, including milk and ice cream.
Fruits cause gas because the body has difficulty digesting the sugar alcohol sorbitol and the simple sugar fructose. Pears, peaches and apples are types of fruit that contain both sorbitol and fructose. Additionally, the soluble fiber in fruits passes into the large intestine along with sorbitol and is broken down by bacteria causing gas production.