Coffee science is confusing at best. In May 2019, a study published in the journal Heart made headlines after suggesting that drinking up to 25 cups of coffee in a day doesn’t have an impact on the stiffness of your arteries.

But all that caffeine could have other consequences, like increased blood pressure, nausea, stomach issues, and headaches. Another study from the University of Southern Australia, published in March 2019 in The American Journal of Clinical Nutrition, puts a much lower limit on the safe daily dose for coffee. That number is six cups of coffee.

Both studies used data from the UK Biobank, which contains information like medical history, genetic profile, diet, exercise patterns, and coffee drinking habits from hundreds of thousands of people. In the March study, the scientists from the University of Southern Australia looked at more than 340,000 people in the database and compared their risk of cardiovascular disease to the amount of coffee they drink every day.

Watch the video above to learn why excess coffee might impact your heart health.

The researchers found that people who drank up to six cups every day were pretty healthy. But the people who drank more than six cups daily had a 22 percent higher risk of heart disease or stroke.

The caffeine in coffee makes your body release adrenaline, the “fight or flight” hormone. That’s why after you drink coffee, you get jittery, nauseous, and sweaty. Your blood pressure also spikes, but after just a few cups, your blood pressure can return to normal levels.

But the scientists found that people who drink more than six cups of coffee every day tended to have a higher average blood pressure than those who did not — and higher blood pressure means higher risk for heart disease.

So if you need a cup of joe — or two, or even five — to get through the day, don’t worry about it. But 25 cups might be a bad idea.

Correction 7/2/19: In this video and in an earlier version of the article, we said high blood pressure is part of the reason coffee drinkers feel jittery, sweaty, and nauseated. High blood pressure does not directly lead to these symptoms. Caffeine causes the body to release adrenaline, which causes the blood pressure to spike and also causes the jitters, lack of concentration, perspiration, and nausea associated with too much coffee consumption.