After drinking coffee stomach upset is because coffee produces a strong stimulation of the stomach, stomach peristalsis becomes faster, so you will feel uncomfortable stomach. People suffering from stomach problems drink coffee stomach upset symptoms will be more obvious, drinking coffee on the stomach to cause adverse effects will be greater, may aggravate the disease. The cautions for drinking coffee are: 1, do not drink too much coffee every day, 2-3 cups a day can help relieve tension at work. 2, drink coffee to drink some plain water, help get rid of oral odor, drink more water to help avoid fire. 3, gastrointestinal disease patients, cardiovascular disease patients, skin disease patients, pregnant women, insomnia patients and other people are not suitable for drinking coffee, to avoid bringing adverse effects on the body. 4, can not drink coffee on an empty stomach, because coffee will stimulate the stomach to secrete more gastric acid, if there is no food in the stomach, gastric acid will produce strong stimulation of the gastric mucosa leading to gastric discomfort.