There are benefits to drinking coffee – but only if you’re having fewer than this number of cups per day
“For years, doctors have said to patients with symptoms of heart palpitations that they should avoid caffeinated coffee because it could worsen them,” says Dr Neil Srinivasan, an NHS consultant cardiologist specialising in heart rhythms.
A new study, published in March, probes that orthodoxy. One hundred healthy volunteers were fitted with a wearable monitor to continuously record their heart rhythm, plus a Fitbit to track their daily steps and sleep patterns, and a blood sugar monitor. Next, they were sent daily text messages instructing them to drink or avoid caffeinated coffee on specific days across a fortnight.
It was a heavy-weight study. Dr Gregory Marcus, who led the research, is a world-renowned heart rhythm expert and, says Srinivasan (who was not involved in the research): “This work is published in the New England Journal Of Medicine – an extremely well- regarded medical journal – so we can certainly trust the legitimacy of it.”
Its findings? In essence: “This new study refutes the common advice,” says Srinivasan. Could coffee actually be good for us?
“The take-home message is that coffee does not cause palpitations and does not need to be restricted,” says Srinivasan.
The study, he explains, did show that coffee-drinking resulted in a slightly increased number of premature ventricular contractions – extra heartbeats that might feel like skips or thuds. “They’re common and usually harmless,” says Srinivasan, “though they do predict the development of atrial fibrillation in some patients – that’s an irregular rhythm of the heart, which can lead to strokes and heart failure.”
Not, though, at the extremely low frequency associated with coffee drinking in this study. “We’re talking extremely small numbers of harmless extra beats within the heart, so most people would not even notice them.”
In fact, the study suggests that, in some ways, coffee might actually be boosting our heart health. People took 1,000 extra steps on coffee days, the equivalent of a half-mile walk which, he says, is obviously good for overall physical and cardiovascular health.
The study also suggested caffeine did not cause spikes in glucose, which might increase the risk of long-term illnesses such as diabetes and atherosclerosis (hardening of the heart arteries), as some past studies have suggested.
That said... study participants slept for around 36 fewer minutes on coffee days (when they tended to drink between one to three cups, though a handful downed up to six).
“We know that sleep is beneficial for overall physical and mental health,” says Srinivasan. But there’s more: “Interestingly, people with genetic variants, which make them break down caffeine faster, experienced less of a sleep deficit, while those with variants that lead them to metabolise caffeine more slowly lost more sleep. So it may be sensible to not drink your last cup of coffee in the evening.”
In 2013, a small study suggested that caffeine can still disrupt sleep six hours after drinking it, so stopping at lunch might be a wise policy. But what else do we know, from other studies, about the health impacts of our favourite addiction?
Coffee’s impact on your risk of developing dementia is still unclear. Some studies have suggested that it has a protective effect, lessening your risk. Others have associated it with no effect or even, in large doses, a raised risk.
Dr Sanjiv Chopra, Harvard professor of medicine and author of Coffee! The Magical Elixir, suggests that the effects may be dose dependent: “Drinking two to four cups likely decreases the risk of developing Alzheimer’s, but consuming more than six cups may increase the risk.”
For Alzheimer’s, as for most serious conditions: “Accompanying inflammation is the enemy,” says Chopra. Here again, your morning coffee could come with benefits: “Coffee drinkers have been shown in some studies to have low levels of inflammatory markers in the blood.” Coffee, he points out, contains chlorogenic acid, “one of the richest antioxidants known to man” (and antioxidants regulate inflammation).
Cancer, diabetes, Parkinson’s and gout
Coffee drinking is also associated with a lower risk of seven cancers, including prostate, liver and breast, as well as Type 2 diabetes, Parkinson’s and gout, says Chopra, largely thanks to these anti-inflammatory properties.
A 2014 meta-analysis found that drinking up to four cups of caffeinated coffee a day was associated with a 25 per cent lower risk of developing diabetes (decaf carried a 20 per cent lower risk), while a 2011 review of research suggested that regular coffee drinkers reduced their risk of developing cancer by 13 per cent, compared to those who seldom or never drank it.
“Coffee contains a significantly larger amount of fibre than other common drinks,” says Dr Emily Leeming, senior nutrition scientist at Zoe, the personalised nutrition company based at King’s College London.
Likely, thanks in part, to this fibre-content, “having more than one cup a day is linked to a more diverse microbiome, and higher amounts of potentially helpful types of gut bacteria,” she says. But coffee’s other super power is its high concentration of polyphenols, antioxidants that are believed to be like food for your gut bacteria: “They’re thought to be the reason why coffee is linked to multiple health effects, from better liver health, mental health and lower risk of type two diabetes.”
How about instant, or even decaf?
“It doesn’t matter if the coffee is instant or decaf,” says Leeming. Chopra agrees. In fact, he is often asked the best way to drink coffee: “My answer? With a friend!” Seriously though, it’s OK to add sugar, milk or cream, if one does not have diabetes. There’s only one absolute no-no – artificial sweeteners. These change the gut microbiome.”
The sweet spot?
Any health benefits are associated with drinking about one to four cups a day, says Leeming. And indeed, the latest study suggests that five cups a day or fewer are unlikely to cause harmful heart rhythm abnormalities in healthy young people.
Chopra, meanwhile, has four cups, making sure to down his last before 4pm to avoid insomnia. That said: “Voltaire, the French philosopher, lived to 83 years at a time when life expectancy was at best, 50 years,” he muses. “He is reported to have consumed 40 to 50 cups every day. Sometimes mixed with cocoa.” So there are always exceptions to the rule.