Researchers from Chalmers University of Technology and Umeå University have identified specific molecules, known as biomarkers, to help differentiate between the impact of filtered and boiled coffee on type 2 diabetes risk.
Results “clearly showed” that filtered coffee had a positive effect in terms of reducing the risk of developing type 2 diabetes, but boiled coffee did not have the same effect, said Rikard Landberg, professor in Food Science at Chalmers, and affiliated professor at the Department of Public Health and Clinical Medicine at Umeå University.
Using a technique called metabolomics in combination with classic dietary questionnaires, the researchers were able to show that people who drank two to three cups of filtered coffee a day had a 60% 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.
Researchers said it was unclear whether instant coffee, the most popular type in the UK, would be more similar to filtered or boiled coffee.
Made possible by metabolomics
Metabolomics made 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, according to Lin Shi, postdoctoral researcher and lead author of the study.
“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,” Shi said.
Filtered coffee is the most common method of preparation in many countries, including the US and Scandinavia. All the data used in the research came from a group of Swedish subjects and was collected in the early 1990s.
Many people wrongly believed that coffee had only negative effects on health, Landberg said. This could be because previous studies had shown that boiled coffee increased 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,” he added. “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.”
Researchers conceded, however, they could not be certain that diterpenes also negatively influenced sugar metabolism and were, therefore, the cause of why boiled coffee does not help lower the risk of diabetes, in the way that filter coffee does.
Landberg believed that espresso coffee, brewed without filters, would produce a similar result to boiled coffee in terms of the risk of type 2 diabetes. Coffee made in a cafetière, or French press, is prepared in a similar way to boiled coffee, so it might also not have the positive effect. He was careful to note that no conclusions could yet be drawn on these other preparation methods.
Ultra-processed food diabetes link
Meanwhile, the latest paper to be published from the French NutriNet-Santé cohort study has found that a higher consumption of ultra-processed food (UPF) may be linked to a higher risk of developing type 2 diabetes.
The study, which observed 104,707 adults, showed the absolute amount of UPF consumption (grams per day) was consistently associated with type 2 diabetes risk, even when adjusting for unprocessed or minimally processed food intake.
Gunter Kuhnle, professor of nutrition and food science, University of Reading, said the observed associations were strong enough to justify more research to understand the underlying reasons. However, he cautioned, the current definition of ultra-processed food was “too unspecific” to derive specific dietary recommendations.
Kevin McConway, emeritus professor of applied statistics at The Open University, said the new study did not throw much new light on how ultra-processed food consumption might possibly be a cause of changes in diabetes risk.
“Better evidence on that might increase confidence that the association is one of cause and effect, to some extent at least,” he added.