High levels of caffeine, abundantly found in tea and coffee and consumed by billions across the globe, in the blood may reduce the amount of body fat and reduce their risk of developing diabetes, researchers of a new study said.

The findings of the collaborative study, published in the open-access journal BMJ Medicine recently, the researchers from the United Kingdom and Sweden investigated the potential role of calorie-free caffeinated drinks in lowering the risks of obesity and type 2 diabetes is probably now worth exploring, researchers said.

Though previous studies have linked the reduction of risk of developing diabetes or cardiovascular diseases with caffeine consumption, they could not establish a causal relationship between the two.

Intending to fill that gap, the current research used Mendelian randomisation, a technique that uses genetic variants as proxies for a particular risk factor, to find out what effect higher blood caffeine levels have on body fat and the long-term risks of type 2 diabetes and major cardiovascular diseases, including coronary artery disease, stroke, heart failure, and irregular heart rhythm.

In the current study, the researchers tried to obtain genetic evidence in support of weight (BMI) and type 2 diabetes risk and investigated the role of two common genetic variants of the CYP1A2 and AHR genes associated with the speed of caffeine metabolism in the body, in nearly 10,000 people of predominantly European ancestry, who were taking part in 6 long term studies.

People who carry genetic variants associated with slower caffeine metabolism drink, on average, less coffee, yet have higher levels of caffeine in their blood than people who metabolise it quickly to reach or retain the levels required for its stimulant effects.

According to the researchers, higher genetically predicted blood caffeine levels were associated with lower weight (BMI) and body fat, as well as a lower risk of type 2 diabetes.

The researchers then used Mendelian randomisation to investigate whether any effect of caffeine on type 2 diabetes risk was primarily driven by concurrent weight loss, and their findings revealed that weight loss was responsible for nearly half (43%) of the effect of caffeine on type 2 diabetes risk.

Furthermore, they found no strong associations between genetically predicted blood caffeine levels and the risk of any of the studied cardiovascular disease outcomes.

Admitting that their study had multiple limitations, including being confined to participants of European ancestry and use of only two genetic variants, the researchers wrote, “Because genetic predictors of plasma caffeine  concentrations in people who are not of European ethnicity are not established and our data sources comprised European individuals only, our findings might not be generalisable to populations of non-European ethnicity.”

“This mendelian randomisation study found evidence to support causal associations of higher plasma caffeine concentrations with lower adiposity and risk of type 2 diabetes,” they added.

“Randomised 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,” the researchers concluded.