Higher genetically predicted blood caffeine levels are associated with lower body weight (BMI) and body fat, an analysis suggests. In addition, higher genetically predicted blood caffeine levels were also associated with lower risk of type 2 diabetes.
The potential role of calorie-free caffeinated beverages may now need to be explored, the researchers said.
High blood caffeine levels may curb the amount of fat the body carries and the risk of type 2 diabetes, suggests a study published March 14 in the open access journal British Medical Journal.
Based on their findings, the researchers say it may now be worth exploring the potential role of calorie-free caffeinated beverages in reducing the risk of obesity and type 2 diabetes.
The researchers point to previously published studies showing that drinking 3-5 cups of caffeinated coffee per day is associated with a lower risk of type 2 diabetes and cardiovascular disease. An average cup of coffee contains about 70-150 mg of caffeine.
But the researchers note that most of the studies published so far have involved observational studies, which cannot reliably establish cause and effect due to the involvement of other potentially influential factors.
Additionally, they add, it can be difficult to separate any specific effects of caffeine from other compounds in caffeinated beverages and foods.
The most popular sources of caffeine in the diet are coffee and tea. According to a survey by the Coffee Association of America, 64 percent of Americans age 18 or older drink coffee daily, while a survey by the Tea Association of America found that 84 percent of Americans drink tea. Other sources of caffeine, such as soft drinks, energy drinks and chocolate products, are also popular, but coffee and tea remain the most widely consumed sources of caffeine.
To try and overcome these issues, the researchers used Mendelian randomization to find out the effect of higher blood caffeine levels on body fat as well as type 2 diabetes and major cardiovascular diseases (coronary artery disease, stroke, heart failure and heart failure) long-term risks. Irregular heartbeat (atrial fibrillation).
Mendelian randomization is a technique that uses genetic variation as a proxy for a particular risk factor (in this case caffeine blood levels) to obtain genetic evidence supporting a particular outcome, in this study body weight (BMI) and Type 2 diabetes risk.
Researchers studied the role of two common genetic variants in the CYP1A2 and AHR genes in nearly 10,000 people of predominantly European descent who participated in six long-term studies. The CYP1A2 and AHR genes are involved in how quickly caffeine is metabolized in the body.
People who carried the genetic variant associated with slower caffeine metabolism drank less coffee on average but had higher levels of caffeine in their blood than those who metabolized caffeine rapidly to achieve or maintain its stimulant effects.
Results of the analysis showed that higher genetically predicted blood caffeine levels were associated with lower body mass (BMI) and body fat.
Higher genetically predicted blood caffeine levels were also associated with lower risk of type 2 diabetes.
The researchers then used Mendelian randomization to further explore the extent to which any effect of caffeine on type 2 diabetes risk was primarily driven by concurrent weight loss.
The results showed that nearly half (43%) of the effect of caffeine on type 2 diabetes risk was due to weight loss.
There was no strong association between genetically predicted blood caffeine levels and risk for any of the cardiovascular disease outcomes studied.
The researchers acknowledge various limitations to their findings, including using only two genetic variants and including only people of European ancestry.
But they explain that caffeine can boost metabolism, increase fat burning and reduce appetite. It is estimated that a daily intake of 100 mg increases energy expenditure by approximately 100 calories per day, thereby reducing the risk of obesity.
“Our Mendelian randomization findings suggest that caffeine may at least partially explain the inverse association between coffee consumption and type 2 diabetes risk,” the researchers wrote.
“Randomized controlled trials are warranted to assess whether calorie-free caffeinated beverages may play a role in reducing the risk of obesity and type 2 diabetes,” they concluded.
Reference: “Assessing causality[{” 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
