Drinking five cups of coffee a day could protect against heart disease and stroke a new study has found – but higher doses of caffeine should be avoided. The latest research – published in the journal of the American Heart Association – suggests that black coffee could have a number of heart health benefits. The US researchers found that consuming coffee without sugar, flavours or milk was linked to a lower risk of type 2 diabetes, heart disease, stroke, heart failure and irregular heart rhythms. It's thought that coffee's protective effect could be due to anti-inflammatory compounds in the beans, known as polyphenols. These antioxidant-rich compounds protect against harmful elements in the atmosphere, improve blood vessel function and lower inflammation – a precursor to major diseases including cancer.Caffeine may offer similar benefits, the researchers say, but these vary more dramatically from person to person. However, higher doses of caffeine can overstimulate the heart, triggering sudden spikes in blood pressure, irregular heart beats and even cardiac arrest in healthy adults. 'Caffeine consumed in coffee is a key part of daily life for millions of people,' Dr Gregory Marcus, chief of cardiology for research at the University of California said. Drinking five cups of coffee a day could significantly slash your risk of heart failure 'In our review of the most recent research, for most adults, intake of up to 400mg of caffeine a day [around five cups] without added sugars is safe and does not increase cardiovascular risk.'However high doses of caffeine, such as those found in energy drinks including energy shots, may have harmful effects on the heart and should be avoided.' The new research marks a major shift by comparing how coffee and synthetic caffeine affect blood pressure, cholesterol, diabetes risk and cardiovascular health. The researchers found that drinking around five cups of coffee a day seemed to decrease the risk of high blood pressure, a major killer that affects around one in three Britons.Drinking one to three cups however was found to spike blood pressure levels, which can increase the likelihood of heart attack and stroke. Daily coffee consumption was also linked with a lower risk of atrial fibrillation – a condition that causes heart palpitations, as well as potentially heart failure, blood clots and strokes. It is a common assumption that consuming caffeinated coffee can trigger an elevated heart rate. But, a 2025 study found that 200 patients with persistent irregular heartbeats had a significantly lower risk of the condition recurring if they drank coffee.