In a good news for coffee lovers, researchers have found that coffee can help reduce the risk of developing type 2 diabetes - but only filtered coffee, rather than boiled coffee.
The study, published in the Journal of Internal Medicine, shows that the choice of preparation method influences the health effects of coffee.
The findings from Chalmers University of Technology and Umea University in Sweden, offer new insight into this connection, using a novel method to help differentiate between the effects of filtered coffee and boiled coffee.
"We have identified specific molecules - 'biomarkers' - in the blood of those taking part in the study, which indicate the intake of different sorts of coffee. These biomarkers are then used for analysis when calculating type 2 diabetes risk," said study researcher Rikard Landberg, Professor at Umea University.
"Our results now clearly show that filtered coffee has a positive effect in terms of reducing the risk of developing type 2 diabetes. But boiled coffee does not have this effect," Landberg added.
With the use of these biomarkers, the researchers were able to show that people who drank two to three cups of filtered coffee a day had a 60 per cent lower risk of developing type 2 diabetes than people who drank less than one cup of filtered coffee a day.
Consumption of boiled coffee had no effect on the diabetes risk in the study.
To differentiate the diabetes risk for boiled and filtered coffee, a new technique called metabolomics was used, in combination with classic dietary questionnaires.
Metabolomics makes it possible to identify the blood concentration of specific molecules from a given food or drink and use that as an objective measurement of intake - instead of simply relying on self-reported intakes from the questionnaires, which are prone to large errors.
"Metabolomics is a fantastic tool, not just for capturing the intake of specific foods and drinks, but also for studying the effects that that intake has on people's metabolism. We can derive important information on the mechanisms behind how certain foods influence disease risk," said study lead author Lin Shi.
According to the researchers, many people wrongly believe that coffee has only negative effects on health.
This could be because previous studies have shown that boiled coffee increases the risk of heart and vascular diseases, due to the presence of diterpenes, a type of molecule found in boiled coffee.
"But it has been shown that when you filter coffee, the diterpenes are captured in the filter. As a result, you get the health benefits of the many other molecules present, such as different phenolic substances. In moderate amounts, caffeine also has positive health effects," Landber said.
Many other types of coffee preparation were not specifically investigated in the study, such as instant, espresso, cafetiere, and percolator coffee.
The study stresses that the health impacts of coffee do not depend solely on if it is filtered or not. They also vary with how the coffee beans, and the drink in general, are managed.
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