Published in European Journal of Nutritionthese results concern more than 2,200 Finns aged 46. They do not prove that coffee transforms the figure or hormones, but open a new avenue for understanding the biological effects of this drink consumed daily by millions of people.
Pound for pound, coffee lovers seem to have different bodies
In Finland, coffee is almost an institution. With approximately
11.8 kilos consumed per person per yearthe country is among the greatest amateurs in the world.
The team from the University of Oulu relied on data from
2,264 participants aged 46from the Northern Finland Birth Cohort 1966. The researchers compared their usual coffee consumption with different metabolic markers, body composition and sex hormones.
First observation: Comparable BMIparticipants who drank the most coffee had less total fat mass and less visceral fat, the fat accumulated around the organs and associated with metabolic disorders. They also had more skeletal muscle mass.
Two people with the same weight could therefore have a different distribution between fat and muscle.
However, the measurement was based on bio-impedancemetry, an indirect method. This result should therefore be considered an interesting signal rather than definitive proof.
Another clue: in both men and women, greater coffee consumption was associated with lower blood levels of
BCAA — leucine, isoleucine and valine in particular. Sustainedly elevated concentrations of these amino acids have previously been associated with insulin resistance and an increased risk of type 2 diabetes.
In men, an astonishing hormonal signature
This is the most original result of the study.
In men who consumed more coffee, researchers observed a more favorable glycemic and insulin profile, but also higher concentrations of
total and bioavailable testosterone as well as an increase in SHBG, a protein that carries sex hormones in the blood.
At the same time, the free testosterone and free androgen index were slightly lower.
This result may seem paradoxical. An increase in total testosterone does not necessarily mean that more of the hormone is available to act on tissues, particularly because some of it circulates bound to proteins like SHBG.
In women, the associations were more discreet: the researchers mainly observed a Higher SHBG and lower levels of free androgenswith no net increase in total or bioavailable testosterone.
“Coffee is consumed by millions of people every day, yet we still know surprisingly little about its relationship to our metabolism and hormones. What stood out in our results was a distinct hormonal signature that did not disappear even after we took into account BMI and lifestyle factors, with several of these associations differing between men and women.”explains Luca Verroest, researcher and lead author of the study.
An intriguing result, but not a reason to increase the number of coffees
These observations must, however, be interpreted with caution. The study is observational : it highlights associations, but does not demonstrate that coffee is directly responsible for the differences observed. The researchers did not ask the participants to modify their consumption in order to then measure the consequences.
Other lifestyle habits could therefore contribute to the results, despite the statistical adjustments made by the team. Coffee consumption was also declared by the participants and body composition was estimated by bio-impedancemetry.
It would therefore be premature to advise drinking more coffee to lose fat, gain muscle or change your hormonal balance.
The interest of the study lies elsewhere: it provides a new avenue to understand why coffee consumption is regularly associated with certain metabolic benefits.
Researchers now want to determine whether coffee actually causes these changes and which compounds might be involved. Work is underway on the biological mechanisms, before possible intervention studies in humans.
One thing is already certain: behind a drink as familiar as a cup of coffee lies a chemistry much more complex than it seems. And research is only beginning to understand how it might interact with our metabolism and hormones.