The Ideal Number of Coffees a Day for a Healthy Heart

Four cups of strong coffee a day might be the recipe for a healthy heart, especially for older adults. A team of German researchers, led by the molecular biologists Judith Haendeler and Joachim Altschmied, thinks it has discovered clues about how coffee works its caffeine-fuelled magic on our heart health and how much caffeine we should drink each day to see the best benefits.

By studying caffeinated lab mice and dosing human tissues with caffeine, the researchers discovered how a jolt of the stimulant could improve the way cells inside our blood vessels work - essentially, by making certain proteins inside older adult cells perform more like young and nimble ones. The study was published Thursday in the journal PLOS Biology.

"When you drink four to five cups of espresso," Altschmied told Business Insider, "that seems to improve the function of the powerhouses of our cells, and therefore seems to be protective." Scientists have for years noticed that people who drink coffee seem to be less likely to die from all sorts of causes, including heart disease, stroke, or diabetes.

Perhaps the best evidence yet for this comes from two massive studies: one of more than 400,000 people in the US by the National Institutes of Health, and another of more than 500,000 Europeans. Both studies found that regular coffee drinkers were less likely to die from any cause than people who don't sip a daily brew.

One caveat: The study wasn't done in humans - only in human tissues and lab mice.