For this reason, coffee use by diabetics must be carefully monitored. Coffee is also tough on people who carry a lot of stress in their lives, because the jangle of life and its natural challenges can be made more acute by a caffeine load. Many long and restless nights result from coffee consumption. Ulcers in the intestine are aggravated by coffee ingestion, as gastric acid goes up after coffee consumption. Not surprisingly, many bellyaches have been helped merely by the restriction of coffee intake.
Coffee also acts as a diuretic.
Not only does coffee provide a fluid load, but caffeine acts to increase blood flow to the kidneys, thereby increasing fluid loss even more. As you age, and try to minimize fluctuations in your fluid balance, this feature is of substantial importance. It is the cardiovascular system that has been most studied with regard to coffee drinking. Ten years or so ago, a number of scientific reports seemed to indicate that coffee drinking increases serum cholesterol levels and causes heart trouble, and so it was considered to be a risk factor for coronary disease. These studies have not been confirmed, however.