Two Cups of Coffee a Day Linked to Lower Heart Risk and Mortality in UK Biobank Study

A study drawing on the health records of more than 400,000 Britons has found that people who drink two to three cups of coffee a day tend to live longer and have fewer heart problems than people who never drink it. The results were presented at an American College of Cardiology meeting in Washington DC.

The international team used data from the UK Biobank, covering people whose intake ranged from up to a cup a day to more than six. They compared those habits against heart rhythm problems, cardiovascular disease, and deaths from all causes and from heart-related causes. The largest group, 382,535 men and women with an average age of 57, had no known heart disease at the start. A second group of 34,279 people already had some form of cardiovascular illness.

The best results appeared at two to three cups a day. Compared with people who never drank coffee, those drinkers had a 10 to 15 per cent lower risk of coronary heart disease, heart failure, a heart rhythm problem, or dying for any reason. Drinking fewer than two cups or more than three did less well. The exception was stroke and heart-related death, where the lowest risk was among people who drank a single cup a day. According to the researchers, the associations held regardless of exercise, alcohol, smoking, diabetes and high blood pressure.

The findings matter most for people who already have heart trouble. Among those with existing cardiovascular disease, two to three cups a day was also linked to lower odds of dying than abstaining. Of 24,111 people in the analysis who had an arrhythmia at the outset, coffee drinking was associated with a lower risk of death. People with atrial fibrillation who drank one cup a day were nearly 20 per cent less likely to die than non-drinkers. Drinking any amount did not raise the risk of rhythm problems, including AFib or atrial flutter.

That last point addresses a long-standing worry. Senior author Professor Peter Kistler of the Baker Heart Institute in Melbourne said coffee can quicken the heart rate, so some people fear it could trigger or worsen certain conditions, and doctors often advise patients with arrhythmias to stop. His reading of the data is that daily coffee should not be discouraged and can be part of a healthy diet for people with or without heart disease. He described the effect as either neutral or beneficial.

Kistler pointed to coffee's more than 100 plant chemicals as a possible explanation. He said they reduce oxidative stress and inflammation, improve insulin sensitivity and metabolism, block fat absorption in the gut, and affect molecules linked to abnormal heart rhythms.

A third analysis compared instant, ground, caffeinated and decaffeinated coffee. Two to three cups a day was again the best intake, and lower death rates appeared across all types. Decaf did not show favourable effects against arrhythmia, though it was associated with lower cardiovascular disease, apart from heart failure. Kistler concluded that caffeinated coffee looks preferable across the board and that there is no benefit in choosing decaf.

The stakes are large: cardiovascular disease kills an estimated 17.9 million people worldwide each year. Coffee has also been linked to lower rates of cancer, dementia, diabetes and depression. The usual advice is to stay under four cups, about 400mg of caffeine, since caffeine is a stimulant that can cause insomnia and muscle tremors.

The study tracked people over time rather than assigning them coffee, and it was presented at a conference. What to watch is whether clinicians who have counselled caution begin to revisit that advice for heart patients.