Caffeine has many known health benefits. Now a new study shows that a lower risk of developing specific diseases is associated with high blood caffeine levels.
Researchers have confirmed numerous times that drinking coffee and is healthy, and caffeine is a key part of this health-promoting effect.
However, researchers have now nuanced this narrative by examining how the blood caffeine level is associated with the risk of developing specific diseases.
The researchers investigated the blood caffeine level rather than the volume of caffeinated beverages drunk during the day, since people metabolise caffeine differently and drinking more coffee can often end up lowering the circulating caffeine level.
“Usually this type of research asks numerous people how many cups of tea or coffee they drink per day. But this does not tell us how much caffeine they have in their blood. This type of question can also lead to error, because people may also add cream or milk and sugar to their coffee, since these can also affect health and reduce the actual amount of coffee consumed. Therefore, we instead investigated the health benefits in relation to how the body metabolises caffeine,” explains a researcher behind the study, Héléne Toinét Cronjé, Postdoctoral Fellow, Section of Epidemiology, Department of Public Health, University of Copenhagen, Denmark.
The research has been published in BMC Medicine.
Genes influencing caffeine metabolism
Instead of investigating the effect of a given quantity of coffee consumed, the researchers used genetically predicted variation in caffeine metabolism as a proxy for the quantity of caffeine in the blood. Previous studies by the same researchers showed that specific genetic variants are associated with blood caffeine levels.
The research also showed that this method combined with large quantities of genetic data can create insight into caffeine metabolism and thereby the blood caffeine levels at the population level.
“Our previous research also showed that higher caffeine metabolism actually drives coffee intake. The higher a person’s caffeine metabolism, the more coffee they drink,” says Héléne Toinét Cronjé.
Associations in data for more than 500,000 people
The researchers used data for more than 500,000 people 40–60 years old from the UK Biobank, including genetic data and information on 988 clinical traits.
This enabled the researchers to link the genetics behind caffeine metabolism, as a proxy for blood caffeine levels, with the risk of developing various diseases.
Specifically, the researchers investigated the significance of genetic variants of the metabolising protein gene, CYP1A2, and its transcriptional regulator, AHR, which determine 90% of how people metabolise caffeine.
The researchers validated their findings in another clinical data set.
High caffeine levels associated with protection against osteoarthrosis and osteoarthritis
The results show very clearly that genetically predicted higher blood caffeine levels are associated with a lower risk of developing overweight, obesity, osteoarthrosis and osteoarthritis.
Héléne Toinét Cronjé says that the associations with overweight and obesity were already known but that the associations with osteoarthritis and osteoarthrosis are new knowledge.
The researchers found the same associations in the second data set, and this was reinforced by the fact that researchers in another study did not find any association among participants who did not drink coffee.
Benefits of caffeine
Finally, the researchers also investigated whether the association between genetically predicted blood caffeine levels and the risk of developing osteoarthrosis and osteoarthritis resulted from the genetic association between osteoarthritis and obesity.
Being overweight or obese because of the genetic association with blood caffeine levels could strain joints more.
This part of the study found that high body mass index mediated only 33% of the association between caffeine metabolism and risk of osteoarthritis. The remainder results from a direct association or a different factor the researchers have not yet identified.
“The conclusion is that people with higher genetically predicted caffeine metabolism have a lower risk of developing osteoarthritis, and only one third of this association can be explained by people with high genetically predicted blood caffeine levels also weighing less,” explains Héléne Toinét Cronjé, who adds that the researchers are not saying that people should drink more coffee.
Instead, she would like the results to be used to increase research on the benefits of having caffeine in the body and how this improves people’s health.
“Our study isolates how blood caffeine levels affect people’s health,” concludes Héléne Toinét Cronjé.
