You should not drink coffee when you are menstruating because individual differences and changes in hormone levels in the body can lead to insomnia or emotional changes during menstruation. The caffeine in coffee has a stimulating effect and can aggravate insomnia, so you should not drink coffee when you have your period. In addition, during menstruation, there are some foods that you should not eat, such as winter melon, barley, pears, bananas, watermelon, etc. These cold foods, if eaten, may cause menstrual cramps. You should also not eat food with lower temperature during menstruation, such as food taken out of the refrigerator, which may stimulate cause vasoconstriction after consumption, and may clinically lead to the possibility of dysmenorrhea. So menstruation is a physiological period for women, but it can also cause serious clinical consequences if you are not careful.