Coffee Drinking Not Linked to Chronic Illnesses

Coffee Drinking Not Linked to Chronic Illnesses

By Kerry Grens

NEW YORK (Reuters Health) Mar 01 - Studies of coffee's links to myriad diseases have provided conflicting results, but a new paper finds coffee drinkers have no higher risk of heart disease, stroke or cancer, and they are less likely to develop type 2 diabetes.

"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 Dr. Rob van Dam of the National University of Singapore, who was not involved in this study.

In some studies, coffee drinking has been tied to an increase in heart disease, cancer, stroke and more. In others, coffee drinking appears benign or even linked to better outcomes.

"There have been conflicting results from previous studies regarding coffee's effect on chronic disease risk depending on the type of disease," said Dr. Anna Floegel, the lead author of the study and an epidemiologist at the German Institute of Human Nutrition Potsdam-Rehbruecke. "That is why we decided to look at different diseases at the same time to estimate the overall health effect of coffee consumption."

The researchers, who published their findings online February 15 in the American Journal of Clinical Nutrition, collected information on coffee drinking habits, diet, exercise and health from more than 42,000 German adults without any chronic conditions.

Nine years later, they found that coffee drinkers and non-drinkers were similarly likely to develop heart disease, stroke, diabetes and cancer.

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% in both groups.

"Our results suggest that coffee consumption is not harmful for healthy adults in respect of risk of major chronic diseases," Dr. Floegel told Reuters Health by email.

On the other hand, coffee drinkers were less likely to develop type 2 diabetes. Among those who consumed four cups a day at baseline, 3.2% developed type 2 diabetes, compared to 3.6% of people who drank no coffee. After adjustment for diabetes risk factors, the researchers determined that frequent coffee drinkers were 23% less likely to develop diabetes.

That squares with other studies. "Higher coffee consumption has been consistently associated with a lower risk of type 2 diabetes in many prospective studies across the world," Dr. van Dam said by email (see Reuters Health report of December 14, 2009).

This doesn't mean that coffee is responsible for preventing type 2 diabetes, however. Although the researchers tried to account for other known diabetes risk factors, there could be inaccuracies in measuring these factors and there could be other, unknown influences too, Dr. van Dam said.

However, experiments in animals have hinted that certain chemicals found within coffee could positively affect metabolism, he noted.

The most notorious component of coffee -- caffeine -- is likely uninvolved, because Dr. Floegel's group found that frequent decaf drinkers also had a lower risk of developing diabetes than people who didn't drink any coffee.

Dr. Floegel said she'd like to see future studies dig down into the possible biological explanations for coffee's role in diabetes, and how people who already have diabetes respond to coffee.

Am J Clin Nutr 2012.