Doctors may never consider coffee a standard recommendation because of individuals' varying susceptibility to side effects, said Hensrud.
Those include headaches, insomnia, heartburn and palpitations, not to mention urinary urgency. People who get fast heartbeats may need to steer clear of caffeinated coffee, too. Others don't drink coffee because it irritates their stomachs.
Famously, coffee got a bad reputation from research in the early 1980s connecting it to pancreatic cancer. But more recent studies have not found the same link, according to the American Cancer Society.
Some studies in the past did not take into account the connection between drinking coffee and smoking cigarettes, which do contain carcinogens, Hensrud said.
Different people metabolize caffeine differently, so some people can have a cup of coffee at night and fall asleep right away, while others need to keep their distance from java for several hours before bedtime to avoid insomnia.
Coffee that's boiled -- popular in Scandinavia, for instance -- will increase bad cholesterol; espresso has the same effect, Hensrud said. But filtering regular coffee reduces those cholesterol-raising substances.
Also, of course, if you don't drink black coffee, cafes will gladly charge you for all kinds of additives to dilute the bitter flavor and strength.
Some milky, sugary coffees may contain upwards of 500 calories -- particularly if they begin with the sound "frap." So, if you think you're doing your body a favor with these treats, health detriments of the added calories and fat may cancel out coffee's magic.
The bottom line
While all the evidence taken together suggests benefits from coffee, the burden of proof still isn't quite strong enough, because these are associations, not a demonstration that coffee causes anything.
"For a public health recommendation, you've got to be pretty darn sure," Hensrud said.
If you don't particularly like coffee but you're thinking about starting to drink it, beware: A sudden change from no consumption can trigger bad consequences, just like doing a really hard workout after you've been a couch potato, Ascherio said. Both situations -- going from nothing to a lot -- can increase risk of heart attack and stroke.
So, if you do feel like trying coffee, start gradually, Ascherio said. It may be that people who experience negative side effects from coffee won't reap the same long-term benefits from it, anyway.
"If you consume coffee, enjoy it," Hensrud said. "But I wouldn't necessarily recommend taking it up if you don't like it."