Drinking coffee each morning does have several health benefits, but too much can raise your risk of cardiovascular disease.

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New research has pinpointed how many cups of coffee are safe to drink each day. Getty Images

A cup of coffee may be just what you need to get going in the morning.

A second cup is to get out the door, and a third (OK, even a fourth) is likely if you’re especially tired.

But if you frequently have half a dozen cups or more, you could be setting yourself up for some serious health complications, a new study in The American Journal of Clinical Nutrition reports.

Australian researchers found that drinking six or more coffees a day increases a person’s risk of heart disease by as much as 22 percent.

In the United States, nearly half of adults has some form of cardiovascular disease, and it’s responsible for one in every four deaths annually.

Americans are also drinking more coffee than ever, too.

A Reuters survey found that 64 percent of Americans over age 18 drink at least one cup a day. That’s up a few percentage points from the year before, and the highest level in half a decade.

Several previous studies have looked at the potential health benefits for the warm brew — and there are many — but few have endeavored to discover at what point the risks of consuming the caffeinated drink begin to outweigh the rewards.

So that’s exactly what Dr. Ang Zhou and Professor Elina Hyppönen of the University of South Australia did.

In the first study to test the upper limits of safe coffee consumption as related to cardiovascular health, the researchers examined how much coffee 347,077 people between the ages of 37 and 73 consumed. They then compared the coffee totals to cardiovascular disease risk.

What they found suggests that the scales move toward risk when you reach the sixth cup of coffee and beyond.

“In order to maintain a healthy heart and a healthy blood pressure, people must limit their coffees to fewer than six cups a day — based on our data six was the tipping point where caffeine started to negatively affect cardiovascular risk,” Hyppönen said in a statement.

Beyond boosting energy, helping you focus, and even preventing yawns in the middle of a business meeting, research has found a myriad of instances when a coffee habit may have some protective health benefits.

“Coffee is the number one source of antioxidants in the human diet — yes, even over wine and tea,” Vanessa M. Rissetto, MS, RD, CDN told Healthline.

“Aside from the caffeine giving you an early-morning energy buzz, those high levels of antioxidants can help protect your body from damage caused by free radicals, as well as fight off disease,” she said.

And the list of potential diseases and conditions that are less common in coffee drinkers is long.

“Caffeinated coffee is associated with lowering the risks for certain cancers and liver disease,” says Kimbre Zahn, MD, Indiana University Health family medicine and sports medicine physician.

Indeed, a 2011 study from Harvard found that regular coffee consumption lowered a person’s risk for developing prostate cancer.

“Daily consumption of three cups of coffee, whether caffeinated or decaffeinated, was associated with a 17 percent lower risk for all-cause mortality compared to no coffee intake,” Dr. Zahn says.

“Caffeinated coffee also conveyed lower risks for cardiovascular disease and stroke with the highest benefits being seen in those consuming between three to five cups per day.”

But lest you start brewing a carafe every morning for these benefits alone, it’s important to understand that coffee is an outsized source of caffeine in the American diet, which can lead to several unintended problems.

“Coffee can cause insomnia, nervousness, restlessness, upset stomach, nausea, and vomiting, increased heart rate and breathing rate, and other side effects,” Rissetto says. “Consuming large amounts of coffee might also cause headache, anxiety, agitation, ringing in the ears, and irregular heartbeat.”

And now, thanks to the study from Prof Hyppönen and Dr. Zhou, we know caffeine can cause high blood pressure, which is a precursor for cardiovascular disease.

It’s not the caffeine alone that can be harmful to a person either. Many coffee drinkers load their java up with cream, sugar, or sweeteners and flavoring ingredients that add calories and fat, which bring a host of their own potential health issues.

“The many ‘add-ons’ that we put in our coffee can have serious negative impacts on our health,” says Dr. Garth Graham, a former deputy assistant secretary at the U.S. Department of Health and Human Services and current president of Aetna Foundation and Vice President for Community Health & Impact for CVS Health.

“Adding syrupy flavorings plus an additional packet of sugar or artificial sweeter, milk, or cream and then topping it all off with a dollop of whipped cream may be a nice treat once in a while, but those who do this regularly are putting themselves at increased risk related to excess calories,” he said.

Instead of thinking about coffee in terms of cups — yes, one coffee cup is about 8 ounces — think about your consumption in terms of total caffeine.

One cup typically equals about 70 to 140 milligrams of caffeine.

If you pop down to your nearest café and order a medium or large coffee, that’s not always one cup (eight ounces) — that’s likely two or even three, and depending on how strong the roast is, it may be even more.

“Although further studies are needed to identify the best amount, in general, consuming less than or equal to 400 milligrams of caffeine a day, or about four or five cups, is what we’d recommend,” Dr. Zahn says.

You can also use online caffeine calculators to account for any and all caffeine you consume.

Remember, coffee isn’t the only source of the stimulant. You can also find it in tea, soda, and sometimes foods.

You can still have your morning coffee — the potential benefits are still real — but if you’ve needed a reason to cut back, this new study finds it.

Once you drink more than six cups in a day, you’re increasing your risk for cardiovascular disease, which might erase any potential benefit from your first five cups.

“We can’t definitively identify a causal link, and these outcomes may be more related to other lifestyle or behavioral choices by the consumer,” Dr. Zahn says. “Therefore, physicians aren’t recommending coffee for prevention of disease or other health reasons, but we know evidence does support the safety of consuming coffee in most cases.”