Drinking just two cups of filtered coffee a day may reduce the risk of type 2 diabetes by 60%, research suggests.
Scientists from the Chalmers University of Technology in Gothenburg looked at biomarkers for boiled or filtered coffee in the blood of more than 800 people.
The found those with more “filtered coffee” markers were less likely to develop the condition over the next seven years. The same was not true for the boiled version of the pick-me-up.
Coffee contains compounds that have been shown to affect the break down of fat, as well as targeting inflammation.
It can also be rich in the molecule diterpene, which negatively influences the metabolism of sugar. This is thought to get caught in filters, preventing it entering coffee prepared this way.
Boiled coffee is typically made by heating a mixture of coarsely ground beans and water, the scientists wrote in the Journal of Internal Medicine.
Filtered coffee starts with finely grounding beans, which are then placed in a filter with water passing through.
When it comes to coffee and health, studies have typically recorded consumption via food questionnaires, which may not specify the brewing method.
To learn more, the scientists looked at participants of the Västerbotten Intervention Programme, aged 40-to-60. They provided blood samples, which were frozen.
The scientists selected 421 of the participants who developed type 2 diabetes around seven years after entering the study. These were matched to 421 healthy “controls”.
The original blood samples were then thawed and checked for coffee biomarkers.
At the same time, an additional 149 diabetic and healthy “pairs” also had their blood assessed.
Results revealed 24 and 32 blood biomarkers associated with boiled or filtered coffee, respectively.
The scientists found an inverse correlation between biomarkers for filtered coffee and type 2 diabetes.
“Our results clearly show 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,” study author Professor Rikard Landberg said.
Drinking just two-to-three cups a day reduced the risk by 60% compared to less than one mug of filtered coffee.
Boiled coffee was found to have no effect, which the scientists put down to diterpene.
“When you filter coffee, the diterpenes are captured in the filter,” Professor Landberg said.
“As a result, you get the health benefits of the many other molecules present. In moderate amounts, caffeine also has positive health effects.”
The scientists predict that due to espresso being brewed without filters, it may have a similar effect to boiled coffee.
The same may also apply to coffee brewed via a cafetière, or French press.
It is unclear whether instant coffee, the most popular in the UK, is more like filtered or boiled varieties, they added.