What causes indigestion?   Some people believe that too much acid in the stomach causes indigestion. However, people with indigestion do not actually produce more acid. It is also commonly believed that too much food or the wrong type of food can cause indigestion. But there is not enough proof that certain foods are the cause of indigestion. Modern research suggests that an important cause of indigestion is food remaining in the stomach discomfort with the feeling of bloatedness and fullness. Indigestion can happen when the stomach is "slow" and cannot empty its contents properly. It can also happen when the stomach is overloaded with a heavy meal. These variety of factors can also contribute to indigestion. This includes stress, lifestyle habits (eg cigarette smoking, alcohol consumption) and the use of certain medicines.