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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 zero-calorie caffeinated beverages may now be warranted, researchers say.
High levels of caffeine in the blood could curb the amount of body fat a person carries and their risk of type 2 diabetes, suggests a study published March 14 in the open-access journal BMJ medicine.
Given their findings, the potential role of zero-calorie caffeinated beverages in reducing the risk of obesity and type 2 diabetes is probably worth investigating now, the researchers say.
Previously published research suggests that drinking 3-5 cups of coffee daily, 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 around 70-150 mg of caffeine.
However, most of the research published to date has involved observational studies that cannot establish reliable causal effects due to the other potential influencing factors involved, the researchers point out.
Additionally, it’s difficult to separate specific effects of caffeine from the other compounds found in caffeinated beverages and foods, they add.
The most popular sources of caffeine in the diet are coffee and tea. According to a survey by the National Coffee Association, 64% of Americans ages 18 and older drink coffee daily, while a survey by the Tea Association of the USA found that 84% of Americans consume tea. Other caffeine sources 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 effects higher blood caffeine levels have on body fat and long-term risks of type 2 diabetes and serious cardiovascular diseases – 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 caffeine levels—to obtain genetic evidence to support a particular outcome—in this study, weight (BMI) and type 2 diabetes risk.
The researchers examined the role of two common genetic variants of the CYP1A2 and AHR genes in nearly 10,000 people, mostly of European descent, who participated in 6 long-term studies. The CYP1A2 and AHR genes are linked to the speed of caffeine metabolism in the body.
People with genetic variants associated with slower caffeine metabolism drink less coffee, on average, but have higher levels of caffeine in their blood than people who metabolize it rapidly to reach or maintain levels needed 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 to what extent caffeine’s effects on type 2 diabetes risk might be primarily due to concomitant weight loss.
Results showed that weight loss accounted for nearly half (43%) of caffeine’s effect on type 2 diabetes risk.
There were no strong associations between genetically predicted blood levels of caffeine and risk of any of the cardiovascular disease outcomes studied.
The researchers acknowledge several limitations to their findings, including using only two genetic variants and including only people of European descent.
But caffeine is known to boost metabolism, increase fat burning and reduce appetite, they explain. And it has been estimated that a daily intake of 100 mg increases energy expenditure by around 100 calories per day, which could consequently reduce the risk of developing obesity.
“Our Mendelian randomization finding suggests that caffeine may at least partially explain the inverse association between coffee consumption and risk of type 2 diabetes,” the researchers write.
“Randomized controlled trials are warranted to assess whether zero-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
