The health benefits of coffee are overwhelming, but getting too much caffeine can be harmful. Here's what research says about the perfect daily dose.
The desire to feel like a functioning human is reason enough for most coffee-lovers to consume the drink on the reg. But for anyone who's not sold, research has also linked coffee to health benefits like a longer lifespan, lowered cancer risk, and boosted athletic performance.
Still, it's always possible to have too much of a good thing—even cold brew. After all, while we know coffee is chock-full of disease-fighting antioxidants like quinines and flavonoids, one espresso shot too many can leave you feeling shaky and anxious, and sometimes with an upset stomach. Plus, too much caffeine has been linked to high blood pressure, which ups your risk of heart disease. (Related: Turns Out It's Possible to Die of a Caffeine Overdose)
So how many cups can you get away with before the risks outweigh the benefits? A new coffee study published in The American Journal of Clinical Nutrition provides an answer. Thankfully, the turning point that researchers landed on is pretty high: six cups per day.
To arrive there, researchers analyzed data from more than 347,000 people, which focused on participants' daily coffee intake and whether they had heart disease. They found that compared to people who drink 1–2 cups per day, those who don't drink coffee have an 11 percent higher risk of heart disease, and those who drink more than six daily cups have a 22 percent higher risk.
"In order to maintain a healthy heart and a healthy blood pressure, people must limit their coffees to fewer than six cups a day," study author, Elina Hyppönen, Ph.D., stated in a press release. "Based on our data six was the tipping point where caffeine started to negatively affect cardiovascular risk."
This isn't the first study to provide a java sweet spot. Here's what else science has to say about your coffee habit.
One to Three Cups a Day
This daily dose may slightly elevate your risk of high blood pressure, a 2011 study in the American Journal of Clinical Nutrition finds. But those who drank less than one or more than three cups a day had no increased risk. Plus, another study found that women who drink two cups a day have an 11 percent lower risk of heart failure than those who drink less, while those who gulp down two to three cups are 25 percent less likely to die from heart disease and 18 percent less likely to die from any cause than non-drinkers, according to research in the Annals of Internal Medicine. (The exception: People who are genetically predisposed to metabolize caffeine slowly. For them, 2–3 cups can raise heart attack risk by 36 percent.)
Three to Five Cups a Day
People who knock back three or four mugs daily have a roughly 25 percent lower risk of developing diabetes than those who drink less than two, according to research presented at the 2012 World Congress on Prevention of Diabetes and Its Complications. (But if you already have diabetes, drinking four servings a day can raise your blood sugar levels by 8 percent, which could worsen your symptoms, another study in Diabetes Journal finds.)
There are mental pluses, too: Three to five cups have been shown to reduce your risk of developing Alzheimer's disease by up to 20 percent. And in addition to reducing your risk of melanoma, four cups a day can lower your chances of dying from oral cancer by 49 percent.
The type of coffee you drink matters, though, say researchers from Baylor College of Medicine: French press brews contain cafestol, a cholesterol-raising compound, which explains why research finds that drinking five cups of it daily can boost levels by 6 to 8 percent. In addition, five cups of regular coffee can impair IVF success by roughly 50 percent. (Related: 15 All-Too-Real Struggles of Having a Coffee Addiction)
Six Cups a Day
The latest American Journal of Clinical Nutrition study suggested that people should cap their coffee intake at five cups per day, but research isn't unanimous. In a study in the New England Journal of Medicine, women who drank six or more cups a day seemed to have a 15 percent lower risk of death than non-coffee drinkers. (Note: Decaf counted toward the women's daily totals.)
At first glance, it looks like the good of drinking coffee—even a lot of it—outweighs the bad, barring any preexisting health conditions like diabetes. But to be sure, we asked coffee expert Rob van Dam, Ph.D., assistant professor in the department of nutrition at the Harvard School of Public Health, for the final verdict.
"We haven’t seen a higher risk of death or disease in people with high coffee consumption, even up to six cups a day, as compared to non-consumers," he asserts. If you’re looking to protect your heart and lengthen your lifespan, he says the evidence points to a "sweet spot" of three to five cups a day—but that’s 8 fl. oz. cups, not the Venti vat you might pick up at Starbucks, which at 20 oz. counts for 2.5 cups alone.
The exceptions include pregnant women (caffeine can harm fetal development), as well as people who find that much caffeine makes them jittery or keeps them up at night. For them, van Dam recommends water and tea. Otherwise, drink away.