By contrast, fats and proteins cause little gas. Foods that can cause gas include: Sugars: The sugars that cause gas are raffinose, lactose, fructose, and sorbitol. Raffinose: Beans contain large amounts of this complex sugar. Smaller amounts are found in cabbage, brussels sprouts, broccoli, asparagus, other vegetables, and whole grains. Lactose: Lactose is the natural sugar in milk.