Common causes of upper intestinal gas include drinking, chewing gum and swallowing more air than usual while eating, while lower intestinal gas is a natural occurrence resulting from the breakdown of food, states the Mayo Clinic. Other causes of gas are some foods and digestive disorders, such as lactose intolerance.
Some specific foods that cause gas are beans, lentils, lactose-based dairy products, fructose and sorbitol, explains the Mayo Clinic. This occurs because these foods are broken down and metabolized into simple substances in the lower intestine or colon, leading to gas. People who have excessive gas more than 20 times per day may have a digestive disorder such as irritable bowel syndrome, dumping syndrome, celiac disease, gastroparesis or a peptic ulcer.
Without the presence of other symptoms, gas is most often not a sign of a serious condition, according to the Mayo Clinic. Normally, gas is simply an indication that a person's digestive system is functioning as it should. Sometimes, dietary changes can help people who feel embarrassed or bothered by gas. It is best to see a physician for gas that is severe or accompanied by symptoms such as vomiting, heartburn, blood in the stool, constipation or weight loss that is not intentional.