Foods that commonly cause gas are carbohydrates, while fats and proteins cause very little gas, according to the International Foundation for Functional Gastrointestinal Disorders. Gas is caused by certain sugars found in foods rather than the foods themselves. These sugars include fructose, lactose, sorbitol and raffinose.
Fructose is found in onions, wheat, pears and artichokes, and it is sometimes used as a sweetener in fruit drinks and soft drinks, according to the IFFGD. Sorbitol is naturally found in many fruits, including prunes, peaches and apples, and it is sometimes used as a sweetener in sugar-free candies, gums and other foods. Raffinose is a complex sugar found in Brussels sprouts, asparagus, broccoli and cabbage. Avoiding these foods can help reduce excess gas.
Lactose is found in milk and dairy products, including ice cream and cheese, and it is also an ingredient in many processed foods such as salad dressings, cereals and breads, according to the IFFGD. Many people have a difficult time digesting lactose and may be lactose intolerant. Over time, people who are lactose intolerant may find it harder and harder to digest lactose and, as a result, may experience worsening gas problems when eating foods that contain it.
Carbohydrate-laden, starchy foods are a major source of gas, according to the IFFGD. These foods include noodles, potatoes and corn.