How much coffee is too much for the heart?

For many people, coffee is the magical brew that kickstarts the day, a much-needed pick-me-up in the afternoon, and sometimes even a well-appreciated digestive after dinner. However, how much coffee is too much? A large new study claims to hold the answer.

“What on earth could be more luxurious than a sofa, a book, and a cup of coffee?” So wrote the Victorian writer Anthony Trollope in his 1855 novel The Warden.

Whatever it is that draws people to coffee — be it its taste and aroma or effects as a stimulant — it is undeniable that this is one of the world’s most popular beverages.

In the United States, coffee drinking has even been on the rise. Statistic reports indicate that, in the 2018/2019 fiscal year alone, people in the U.S. have consumed almost 26.5 million 60-kilogram bags of coffee.

According to the same reports, this is significantly more than they consumed during the previous fiscal year.

Other statistics show that for 2018, almost half of young adults (aged 18–24) reported drinking coffee, and approximately three-quarters of older adults reported the same.

Many recent studies have suggested that drinking coffee can bring a number of benefits in addition to enhancing focus and productivity. In fact, researchers have argued that coffee can help maintain brain health, help increase a person’s lifespan, and even slow down prostate cancer.

However, as with any food or beverage — even the most nutritious and healthful ones — there is a limit to how much coffee we can consume.

Not only can drinking too much coffee create ill effects in the short-term — some of the symptoms of overcaffeination are headaches, dizziness, and nausea — but consistently having too much of this drink could increase a person’s risk of developing cardiovascular disease.

How much is “too much” for the heart? This is the question that scientists at the University of South Australia in Adelaide aimed to answer in their new study, the findings of which now appear in The American Journal of Clinical Nutrition.

The researchers build on previous studies indicating that people with a specific variant of the gene CYP1A2, which plays a key role in caffeine metabolism, metabolize this substance less efficiently. This can put them at an increased risk of developing high blood pressure (hypertension) and cardiovascular disease.

In the new study, the investigators wanted to determine how much coffee would increase the cardiovascular risk of people with and without this genetic variant.