An analysis showed that higher genetically predicted blood caffeine levels were associated with lower weight (BMI) and body fat. In addition, higher genetically predicted blood caffeine levels were also associated with a lower risk of type 2 diabetes.
Research into the potential role of calorie-free caffeinated beverages may now be warranted, researchers say.
High levels of caffeine in the blood may reduce the amount of body fat a person carries and reduce the risk of type 2 diabetes, suggests research published March 14 in the open access journal BMJ medicine.
In light of their findings, the potential role of calorie-free caffeinated beverages in lowering the risks of obesity and type 2 diabetes is now likely worth investigating, the researchers say.
Previously published research indicates that drinking 3-5 cups of coffee a day, a rich source of caffeine, is associated with a lower risk of type 2 diabetes and cardiovascular disease, the researchers note. An average cup of coffee contains about 70-150 mg of caffeine.
But most of the research published to date has been observational studies, which cannot reliably establish causal effects because of the other potentially influential factors involved, the researchers point out.
What’s more, it’s difficult to distinguish specific effects of caffeine from the other compounds in caffeinated drinks and foods, they add.
The most popular sources of dietary caffeine are coffee and tea. According to a survey by the National Coffee Association, 64% of Americans aged 18 or older drink coffee every day, while a study by the Tea Association of the USA found that 84% of Americans consume tea. Other sources of caffeine such as soft drinks, energy drinks and chocolate products are also popular, but coffee and tea remain the most commonly consumed sources of caffeine.
To solve these problems, the researchers used Mendelian randomization to find out what effect higher blood caffeine levels have on body fat and the long-term risks of type 2 diabetes and serious cardiovascular disease – coronary artery disease, stroke, heart failure and irregular heart rhythm ( atrial fibrillation).
Mendelian randomization is a technique that uses genetic variants as proxies for a particular risk factor – in this case, blood levels of caffeine – to obtain genetic evidence to support a particular outcome – in this study, weight (BMI) and type 2 diabetes risk.
The researchers looked at the role of two common genetic variants of the CYP1A2 and AHR genes in nearly 10,000 people of predominantly European descent, who participated in 6 long-term studies. The CYP1A2 and AHR genes are associated with the rate of caffeine metabolism in the body.
People who carry genetic variants associated with slower caffeine metabolism drink less coffee on average, yet have higher levels of caffeine in their blood than people who metabolize it quickly to reach or maintain the levels necessary for its stimulant effects.
The results of the analysis showed that higher genetically predicted blood caffeine levels were associated with lower weight (BMI) and body fat.
Higher genetically predicted blood caffeine levels were also associated with a lower risk of type 2 diabetes.
The researchers then used Mendelian randomization to further investigate the extent to which an effect of caffeine on the risk of type 2 diabetes may be mainly due to the concomitant weight loss.
The results showed that weight loss accounted for nearly half (43%) of caffeine’s effect on type 2 diabetes.
No strong associations emerged between genetically predicted blood caffeine levels and risk of any of the cardiovascular disease outcomes studied.
The researchers acknowledge several limitations of their findings, including the use of only two genetic variants and the inclusion of only people of European descent.
But caffeine is known to boost metabolism, increase fat burning and reduce appetite, they explain. And it is estimated that a daily intake of 100 mg increases energy expenditure by about 100 calories per day, which could consequently reduce the risk of developing obesity.
“Our mendelian randomization finding suggests that caffeine could explain, at least in part, the inverse association between coffee consumption and risk of type 2 diabetes,” the researchers write.
“Randomized controlled trials are warranted to assess whether no-calorie caffeinated beverages may play a role in reducing the risk of obesity and type 2 diabetes,” they conclude.
Reference: “Assessment of the Causal Effect of[{” attribute=””>plasma caffeine on adiposity, type 2 diabetes, and cardiovascular disease: two sample mendelian randomisation study” by Susanna C Larsson, Benjamin Woolf and Dipender Gill, 14 March 2023, BMJ Medicine.
DOI: 10.1136/bmjmed-2022-000335
Funding: Swedish Research Council for Health, Working Life and Welfare; Swedish Heart Lung Foundation; Swedish Research Council