The bad rep: Coffee can make you super-jittery, interfere with your sleep and, well, it’s just not good for you.
The good news: Studies show that compounds in coffee—including but not limited to caffeine—may reduce the risk of dementia, diabetes and liver cancer. Most benefits are associated with drinking 2 to 4 (8-ounce) cups a day. That said, coffee can make some people jittery—and if this is true for you, you should cut back. You should also limit caffeine if you’re pregnant—The American Congress of Obstetrics and Gynecology advises no more than two cups a day while expecting—or nursing.