Apples contain fruit acid, and people's stomachs are empty when they get up in the morning. Once something is eaten, gastric acid will be secreted faster. When gastric acid is added with fruit acid, people's stomachs will naturally be stimulated by strong acidity, so the stomach wall will feel burning pain, which means stomachache. Therefore, it is best to get up in the morning after eating a little bread and milk, and finally eat fruits such as apples and bananas, which is more in line with the law of nutrient absorption. For people with gastrointestinal diseases, it is generally necessary to abstain from cold food, especially eating apples on an empty stomach in the morning, which may cause stomach discomfort.