Coffee drinkers have no more risk of getting illnesses such as heart disease or cancer, and are less likely to develop type 2 diabetes, according to a German study involving more than 40,000 people over nearly a decade.
The findings, published in the American Journal of Clinical Nutrition, came in the wake of many previous studies that produced conflicting results, with some tying coffee drinking to an increase in heart disease, cancer, stroke and more.
"Our results suggest that coffee consumption is not harmful for healthy adults in respect of risk of major chronic disease," said Anna Floegel, lead author of the study and an epidemiologist at the German Institute of Human Nutrition Potsdam-Rehbruecke.
The researchers collected information at the beginning of the study on coffee drinking habits, diet, exercise and health from more than 42,000 German adults without any chronic conditions.
For the next nine years, the team followed up on the participants every two or three years to see whether they developed any health problems, particularly cardiovascular disease, stroke, heart attack, diabetes and cancer.
They found that coffee drinkers and non-drinkers were similarly likely to develop one of those illnesses.
For instance, 871 out of 8,689 non-drinkers developed a chronic disease, compared to 1,124 out of 12,137 people who drank more than four cups of caffeinated coffee a day -- about 10 percent in both groups.
On the other hand, the researchers found that coffee drinkers were less likely to develop type 2 diabetes, the form that does not need insulin and is linked with obesity, than those who didn't drink coffee.
Among those who drank four cups a day, 3.2 percent later reported that they had type 2 diabetes, compared to 3.6 percent of people who drank no coffee.
After taking into account factors that could influence diabetes, such as weight and smoking, the researchers determined that frequent coffee drinkers were 23 percent less likely to develop diabetes, a result that squares with other studies.
That doesn't mean that coffee is responsible for preventing type 2 diabetes, but experiments in animals have hinted that certain chemicals found within coffee could positively affect metabolism.
"We do not encourage people to start drinking coffee if they do not enjoy this, but the overall evidence on coffee and health suggests that there is no reason for persons without specific health conditions to reduce their coffee consumption in order to reduce their risk of chronic diseases," said Rob van Damn, a professor at National University of Singapore, who was not involved in the study.