You can usually reduce the discomforts resulting from the expansion of trapped gases by slowing your rate of ascent. If they persist, descend to a lower altitude where the atmosphere is denser. Most of the gas in the intestines is swallowed air, but some is formed by the digestive process. The amount of gas varies with the individual and with the type of food eaten. If you expect to fly at high altitude, the following "Diet Don'ts" may help to minimize abdominal gas