New research has found a possible link between having high levels of caffeine in your blood and a reduced risk of high body fat and type 2 diabetes. The authors say that clinical trials should be done to confirm whether calorie-free caffeinated drinks can help prevent these conditions.
Past studies have suggested a positive connection between coffee/caffeine consumption and reduced diabetes risk. But this research has largely relied on observational data, which can only point to a correlation between two factors, not show a direct cause-and-effect link. In this new study from scientists in Sweden and the UK, they decided to take a different approach, using a method called Mendelian randomization. The method tries to test whether having known genetic factors for one thing can directly affect the odds of the second factor.
In this case, the team focused on two common genetic variants that seem to slow down people’s metabolism of caffeine. As a result, these people tend to have higher blood caffeine levels, despite actually drinking less caffeinated beverages on average. Analyzing data from around 10,000 volunteers enrolled in other long-term studies, they tracked whether individuals carrying the variants were less likely to develop type 2 diabetes, cardiovascular disease, and other risk factors linked to both.
Overall, they found that people genetically predisposed to high blood caffeine levels were indeed less likely to have a high body mass index, high body fat, and type 2 diabetes. They also calculated that about 43% of this lower diabetes risk was attributable to being lower weight. However, they didn’t see any strong link between these variants and a changed risk of cardiovascular disease. The team’s findings were published Tuesday in the BMJ.
There are limitations to the findings, the authors acknowledge. For one, the sample comes almost entirely from people of European ancestry. The use of only two caffeine-related variants in the analysis also weakens any conclusions that can be drawn from it. And while Mendelian randomization is generally better at supporting a causal relationship between two factors than other types of studies, it’s still not a smoking gun —some studies using this same method haven’t found strong evidence between coffee consumption itself and lower diabetes risk.
That said, there are plausible mechanisms for how caffeine could lower diabetes risk. Caffeine is a stimulant, for instance, which can have short term effects on people’s appetite, and it might also increase people’s ability to burn fat or expend energy. At the very least, the authors say, it’s worth spending more resources to help settle this question.
“Randomized controlled trials are warranted to assess whether non-caloric caffeine-containing beverages might play a role in reducing the risk of obesity and type 2 diabetes,” they wrote.