What is the healthiest way to brew a fresh cup of coffee? A new study investigating the links between methods of brewing coffee and risks of heart attacks and death has concluded that filtered coffee is the safest.
“Our study provides strong and compelling evidence of a link between coffee brewing methods, heart attacks and longevity,” said Professor Dag S. Thelle, author of the study at the University of Gothenburg, Sweden. “Unfiltered coffee contains substances that increase the cholesterol level in the blood. Using a filter removes them and makes heart attacks and premature death less likely.”
Coffee is one of the most popular beverages and the most widely used stimulant worldwide. About 30 years ago, Professor Thelle found that drinking coffee was associated with elevated total cholesterol and "bad" LDL cholesterol — to such an extent that it was likely to have adverse effects on heart health. Experiments identified the culprits in coffee and found that they could be removed with a filter. A cup of unfiltered coffee contains about 30 times the concentration of the lipid-boosting substances compared to filtered coffee.
He said:“We wondered if this effect on cholesterol would lead to more heart attacks and death from heart disease. But it was unethical to do a trial where people were randomized to drink coffee or not. That is why we set up a large population survey and we report the results several decades later.”
Between 1985 and 2003, the study included a representative sample of the Norwegian population:508,747 healthy men and women aged 20 to 79. Participants completed a questionnaire about the amount and type of coffee consumed. Data was also collected on variables that can influence both coffee consumption and heart disease so that they could be factored into the analysis. For example, smoking, education, exercise, height, weight, blood pressure and cholesterol.
Participants were followed for an average of 20 years. In total, 46,341 participants died. Of those, 12,621 deaths were due to cardiovascular disease. Of the cardiovascular deaths, 6,202 were caused by a heart attack.
In general, drinking coffee was not a dangerous habit. Drinking filtered coffee was even safer than no coffee at all. Compared to no coffee, filtered coffee was associated with a 15% reduced risk of death from any cause during follow-up. For death from cardiovascular disease, filtered coffee was associated with a 12% reduced risk of death in men and a 20% reduced risk of death in women compared to no coffee. The lowest mortality was among consumers of 1 to 4 cups of filtered coffee per day.
Professor Thelle said:“The finding that those who drank the filtered drink did slightly better than those who drank no coffee at all could not be explained by any other variable, such as age, gender or lifestyle habits. So we think this observation is true.”
Filtered coffee was also less risky than the unfiltered for death from any cause, death from cardiovascular disease, and death from heart attacks. "Our analysis shows that this was partly due to the cholesterol-raising effect of unfiltered coffee," says Professor Thelle.
Professor Thelle noted that unfiltered coffee did not increase the risk of death compared to coffee abstinence – except in men aged 60 and older, where unfiltered coffee was associated with increased cardiovascular mortality.
He said:“We only had one measure of coffee consumption, but we know that brewing habits in Norway changed during the follow-up period. We think that some women and younger men who drink unfiltered coffee switched to filtered, reducing the strength of the association with cardiovascular mortality, while older men were less likely to change their habits.”
Professor Thelle emphasized that these are observational data, but if public health authorities asked him for advice it would be:"For people who know they have high cholesterol and want to do something about it, stay away from unfiltered brew, including coffee made with a cafetiere. And for everyone else, drink coffee with a clear conscience and go for filtered.”