The breakdown of foods such as beans and certain fruits and vegetables, combined with the swallowing of air, causes excessive gas in the digestive tract, according to the National Institute of Diabetes and Digestive and Kidney Diseases, or NIDDK. Conditions such as lactose intolerance also cause excessive gas.
Foods that contain carbohydrates can cause gas, though whether the level of gas produced is excessive depends on a person's ability to digest those foods, notes the NIDDK. Beans, along with vegetables such as broccoli, cauliflower, asparagus and cabbage can cause gas, as can fruits such as apples, pears and peaches. Fruit drinks, especially those containing apples and pears, and other drinks that use sweeteners made from corn, also contain the carbohydrates that produce gas. Milk and milk products, as well as foods that contain lactose, such as some salad dressings and breads, can also cause excessive gas. Whole grains such as wheat and bran can also cause excessive gas in the intestinal tracts of those who have difficulty digesting those foods.
Activities such as eating or drinking quickly, smoking, chewing gum and drinking carbonated drinks can lead to an increase in the amount of air swallowed, which in combination with the breakdown of foods containing carbohydrates, can lead to excessive gas, states the NIDDK. People can track the causes of their excessive gas by keeping a list of foods they eat to identify when gas occurs.