Coffee is generally recommended to be consumed about half an hour after breakfast. It may generally work better when consumed after the morning meal. Because the main component of coffee is caffeine, there are some sugar, fat, protein, fiber and some acidic substances. These substances can stimulate the secretion of stomach acid, especially caffeine. Morning gastrointestinal function is not fully in a functional state, drinking coffee on an empty stomach may cause stomach discomfort. Drinking after a meal can reduce the secretion of stomach acid, while promoting the absorption of other nutrients, playing a synergistic role, but also to refresh the brain and improve efficiency, but need to be careful not to drink too much. Coffee is generally not recommended to drink before bedtime or under stressful conditions, because caffeine has a stimulating effect on the central nervous system, which may lead to insomnia or accelerate anxiety symptoms.