Coffee is also a bit more complex to study than some other food items. Drinking coffee often goes along together with cigarette smoking, and with a lifestyle that’s not very health conscious. For example, people who drink lots of coffee tend to exercise less. They are less likely to use dietary supplements, and they tend to have a less healthful diet. So in the early studies on coffee and health, it was hard to separate the effects of coffee from the effects of smoking or other lifestyle choices.