Coffee drinkers can now rejoice - drinking coffee has been associated with a reduced risk of death from various causes, including stroke and digestive diseases. Scientists found that this was the case in 10 European countries.
Worldwide, many people consume coffee. It is estimated that more than 2 billion cups of coffee are drunk worldwide every day.
Many studies have shown that the beverage had a beneficial impact on the health, with higher consumption linked to lower levels of inflammation and to a lower risk of diabetes. There has also be some indication that coffee could reduce the risk of liver disease and Parkinson's disease.
However, the published data has at times been confusing especially when scientists investigated the relationship between coffee drinking and risk of death. Studies that have hinted that a higher consumption of coffee is related to a lower risk for all-cause death have often been limited in size and inconsistent.
The research now published in the Annals of Internal Medicine is the largest and one of the most robust to date to address this question. It looks at the coffee consumption of 521,330 people enrolled in a large European cohort study known as the European Prospective Investigation into cancer and nutrition (EPIC).
"Large US and Japanese studies have previously found that drinking more coffee was related with a lower risk of death. However, in European populations, where coffee consumption and preparation methods are variable, the relationship was less certain as relatively small studies had previously been conducted," study co-lead author Neil Murphy, from the Section of Nutrition and Metabolism at the International Agency for Research on Cancer, told IBTimes UK.
Different coffee habits
The participants included in the study came from 10 European countries. They filled in questionnaires regarding their lifestyle and diets, including coffee consumption. They were followed up for 16 years during which almost 42,000 of them died from a range of conditions including cancer, circulatory diseases, heart failure and stroke.
The scientists analysed the data, and after statistical adjustment to take into account lifestyle factors such as diet and smoking, they established that the group with the highest consumption of coffee had a lower risk for all causes of death, compared to those who did not drink coffee. This effect was not only seen with coffee that contained a lot of caffeine - decaffeinated coffee had a similar effect.
Drinking coffee also appeared to reduce the risk of death from specific causes, including digestive diseases, circulatory diseases and liver cancer. However, higher coffee intake was also linked to a higher risk of ovarian cancer.
The fact that Europeans have different coffee habits from one country to the next allowed the researchers to check that it was coffee in itself, and not the way it is prepared, which was having an impact on people's health.
"We found that higher coffee consumption was associated with a lower risk of death from any cause, circulatory diseases, and digestive diseases. Importantly, these results were similar across all of the 10 European countries, with variable coffee drinking habits and customs," Murphy added.
The benefits of drinking coffee
These findings do not mean that people should rush to drink litres of coffee everyday. This is an observational study and it is not able to demonstrate that coffee is responsible for a reduced risk of death - it merely highlights a strong correlation.
Furthermore, it is still unclear how coffee acts on the body to improve people's health. More experimental research will be needed in coming years to shed light on the chemical compounds in coffee that are exerting a protective effect.
Scientists are similarly unsure why a higher risk of ovarian cancer was observed among coffee drinkers in this analysis.
"We do not fully understand the possible mechanisms underlying the coffee and mortality association. Coffee contains numerous chemical compounds, such as polyphenols which have antioxidant effects and other health promoting properties," Murphy explained.
"In our study we observed that compared to non-coffee drinkers, those drinking coffee had healthier liver enzyme profiles, lower inflammation, and better glucose control so it's possible that coffee could be having beneficial effects by impacting on these pathways. However, I would stress that more research is needed."
Although we are not yet at the stage where clinicians should recommend that people include more coffee into their diets, the study suggests that drinking coffee everyday is not necessarily detrimental to the health.
"This study is a careful analysis that factors in potential confounders in the statistical analysis. However, this is an observational study, and coffee intake was only measured once at baseline - so we do not know if this remains the same over time or not," said Clare Collins, Professor in Nutrition & Dietetics at the University of Newcastle (Australia), who was not involved in the study.
"However, the findings suggest that for many people, drinking coffee is fine, and they do not need to stop drinking it with some exception, which may include women at risk of ovarian cancer. For those who like coffee but are sensitive to caffeine, or have heart conditions or high blood pressure, they can use decaffeinated coffee."
To reduce the risk of cancer, digestive disease and heart and circulatory disease, the best evidence-based advice to date remains to stop smoking, improve our diets, treat cholesterol and blood pressure, and exercise more.