March 17, 2023 -- Having a higher level of caffeine in your blood could reduce body fat and the risk of type 2 diabetes, according to a new study published in BMJ Medicine.
Although additional research is needed, the findings open possibilities about the role that calorie-free caffeinated drinks could play in lowering the risks for obesity, diabetes, and other conditions.
“Caffeine has been implicated in affecting metabolism and is commonly consumed in drinks. It is therefore important to better understand what causal effect it might have on metabolism,” said senior study author Dipender Gill, PhD, professor of epidemiology at Imperial College London.
“However, we would like to emphasize that individuals should not change their dietary preferences or lifestyle based on the findings of our study alone,” he said. “Further validation in the form of clinical trials is warranted first. Furthermore, too much caffeine can also have harmful effects, so a balance is necessary.”
Previous studies have found that drinking 3-5 cups of coffee per day is associated with a lower risk of type 2 diabetes and heart disease and drinking 100 milligrams of caffeine per day can increase energy expenditure by about 100 calories per day. An average cup of coffee contains about 70-150 milligrams of caffeine.
However, most of the published research has focused on observational studies, which don’t prove cause and effect. Plenty of other factors could be involved, including other ingredients in caffeinated drinks and foods, according to lead author Susanna C. Larsson, PhD, of the Karolinska Institute in Stockholm, Sweden, and colleagues.
Katarina Kos, MD, PhD, a senior lecturer in diabetes and obesity at the University of Exeter, UK, agrees. She said that this genetic study "shows links and potential health benefits for people with certain genes attributed to a faster [caffeine] ... metabolism as a hereditary trait and potentially a better metabolism."
"It does not study or recommend drinking more coffee, which was not the purpose of this research," she told the U.K. Science Media Centre. Kos wasn’t involved with this study.
In the new analysis, the researchers examined data from 10,000 people mainly of European ancestry who participated in six long-term studies.
They examined two specific genetic mutations that have been linked to a slower speed of caffeine metabolism. In general, people with these two common genetic variants will have higher levels of caffeine in their blood after consuming coffee, or other caffeinated drinks, than those with faster caffeine metabolism.
They then looked at how caffeine levels tracked with body fat, risk of type 2 diabetes, and risk of major heart conditions such as coronary artery disease, stroke, heart failure, and irregular heart rhythm.
The two gene variants resulted in "genetically predicted, lifelong, higher plasma caffeine concentrations," the researchers note "and were associated with lower body mass index and fat mass, as well as a lower risk of type 2 diabetes."
There weren’t any strong associations in this study with a lower risk of developing any of the major heart conditions.
They found that weight loss contributed to about 43% of the effect of caffeine on type 2 diabetes risk.
“The finding that higher plasma caffeine levels may reduce bodyweight and risk of type 2 diabetes seems to fit with what is known about its effects on metabolism,” Gill said. “We are now exploring the broader effects of caffeine on health outcomes and potential mechanisms that may be mediating this.”
The researchers noted several limitations, including that they only studied two genetic variants and that the study participants had predominantly European ancestry. They also emphasized caution about drawing strong conclusions or changing behaviors.
Kos agrees. “When considering coffee consumption and caffeine-containing energy drinks, one must be mindful of the potential negative offset by surplus calories in the form of sugar and fat in many of these drinks,” she noted.
“Even for the option of increasing the use of calorie-free caffeine drinks, a benefit has yet to be proven,” Kos said.