Researchers at the University of Oulu analyzed information from 2,264 people who were 46 years old and taking part in the Northern Finland Birth Cohort 1966. The team investigated how participants' usual coffee intake related to circulating metabolites, indicators of cardiometabolic risk, and sex hormone levels.

Coffee Drinkers Had Less Fat and More Muscle

People who consumed more coffee tended to have lower levels of both total body fat and visceral fat, along with greater skeletal muscle mass. These differences appeared even though participants with higher and lower coffee intake had a similar body mass index (BMI).

Higher coffee consumption was also associated with lower circulating concentrations of branched-chain amino acids in both men and women. When chronically elevated, these biomarkers have previously been associated with insulin resistance and a greater risk of developing type 2 diabetes.

Coffee Intake Was Linked to Different Hormone Patterns

Some of the clearest differences appeared among men. Greater coffee consumption was associated with a more favorable glucose-insulin profile, higher levels of total and bioavailable testosterone, and greater concentrations of sex hormone-binding globulin (SHBG). However, free testosterone and the free androgen index were modestly lower.

The hormonal associations were less extensive in women. Higher coffee consumption was mainly associated with increased SHBG and lower measures of free androgens.

"Coffee is consumed by millions of people every day, yet we still know surprisingly little about how it relates to our metabolism and hormones. What stood out in our findings was a distinct hormonal signature that didn't disappear even after we took into account BMI and lifestyle factors, with several of these associations differing between men and women," says Luca Verroest, lead author of the study and Doctoral Researcher at the University of Oulu.

Hormones Could Offer a Clue to Coffee's Health Links

The findings raise the possibility that hormonal pathways could help explain some of the previously observed relationship between coffee consumption and metabolic health. Because the research was observational, however, it cannot establish that drinking coffee directly caused any of the biological differences identified in the study.

The setting also makes the research especially relevant. Finland ranks among the world's highest coffee-consuming countries, with average annual consumption of approximately 11.8 kilograms (26 pounds) per person.

Researchers say the results offer a starting point for studies designed to determine whether coffee itself produces these biological changes and, if so, which compounds may be responsible. Scientists are currently investigating these questions using animal models, with the longer-term aim of moving toward human intervention studies.

Additional research will be necessary before the findings can be used to shape dietary recommendations.

The study, "Associations of habitual coffee intake with testosterone and cardiometabolic markers: the Northern Finland Birth Cohort 1966 study," was published in the European Journal of Nutrition.