It's long been established that coffee is kind of a wonder drink—research links it to a reduced risk of type 2 diabetes, dementia, heart attack, stroke, and liver cancer; and the caffeine in coffee can even help rev your metabolism, potentially spurring weight loss. So you should have no second thoughts about drinking as many cups a day as you want, right? No such luck. Due to its caffeine content, there's a limit to the amount of coffee (and other caffeinated beverages) you can consume if you're concerned about jitters, heartburn, insomnia, anxiety, and other more serious side effects. "In general, the benefits in these studies tend to be capped at five 8-ounce cups a day," says Frances Largeman-Roth, RDN, a nutritionist and author of Eating in Color. That works out to about 400 mg of caffeine per day—the same cap recommended by the USDA in the newest dietary guidelines. But the amount you can safely consume may be a bit higher. Harvard epidemiologist Rob van Dam, PhD, says his research has found no increased risk of death from any cause in people who drank up to six cups daily. Pretty much everyone agrees, however, that you should never surpass (or even get close to) the National Institutes of Health's marker for "excessive" coffee consumption—10 8-ounce cups. Of course, there are exceptions to those general rules (except the 10-cup one; we're pretty adamant about that!): If you have difficulty controlling conditions like high blood pressure, diabetes, anxiety, or gastroesophageal reflux disease (GERD), it may be a good idea to see if cutting back on coffee or switching to decaf helps, experts say. And even if you're healthy, coffee's effect on the body is highly individual. Research has found that people with certain gene variants actually metabolize caffeine faster in the liver; as a result, they can consume more without the unpleasant side effects. This goes in the other direction, too—if you're a slow caffeine metabolizer, just half a cup could leave you feeling jittery. So, if you're one of those people who can drink your fourth iced coffee at 5 p.m. and still sleep soundly, then there's probably no reason to cut back (though you may want to make your own cold brew); and if just one cup makes you bounce off the walls, keep your intake low. For both groups, however, van Dam recommends trying not to exceed your typical daily consumption by much—your body likes consistency. Source
