The Multifaceted Benefits of Coffee
At this point, it should come as no surprise that coffee is much more than just a morning beverage. Its composition encompasses hundreds of bioactive substances capable of interacting with various processes within the body. It can alter gut flora, elevate mood, reduce the risk of dementia, and even protect the heart—provided it is not consumed at excessively high temperatures. However, numerous mysteries remain regarding the relationship between habitual coffee consumption, metabolism, cardiovascular health indicators, and potentially, sexual hormones.
A recent study published in the European Journal of Nutrition sheds light on these aspects, offering new insights that may fall under the category of “coffee benefits.” Researchers from the University of Oulu in Finland—one of the highest coffee-consuming countries globally—analysed data from a cohort of 2,264 adults with an average age of 46.
The findings unveiled some surprising associations that varied by sex. Notably, men who consumed higher amounts of coffee exhibited elevated levels of total testosterone, while both genders displayed links between coffee intake and specific metabolic indicators.
Body Composition Insights
The researchers categorised participants into four groups based on their coffee consumption: non-drinkers, those who consumed between one and two cups per day, those who drank three to four, and those who indulged in five or more cups.
Differences in body composition were particularly striking. Participants with higher habitual coffee consumption tended to have a lower percentage of body fat, reduced fat mass, diminished visceral fat (the type that accumulates around internal organs), and increased skeletal muscle mass. Yet, measures such as body mass index (BMI), waist circumference, and waist-to-hip ratios were similar across all groups, suggesting that BMI alone does not encapsulate the differences observed in body composition.
Insights from Blood Metabolites
Another significant finding emerged from the analysis of blood metabolites—molecules involved in the body’s chemical processes. In both men and women, higher coffee consumption correlated with lower circulating levels of three branched-chain amino acids: leucine, isoleucine, and valine. These BCAAs are crucial for various metabolic functions, and their elevated blood concentrations have been associated with insulin sensitivity issues and an increased risk of type 2 diabetes.
The metabolic patterns were more pronounced in men. For this group, coffee consumption was also linked to more favourable indicators of glucose and insulin regulation. In contrast, women’s associations were fewer and primarily focused on other markers related to metabolism and body composition.
Exploring Hormonal Connections
One of the most intriguing hormonal findings was the association between coffee consumption and different forms of testosterone in men. After adjusting for factors such as BMI, education level, smoking, physical activity, and alcohol consumption, researchers found that each additional cup per day was associated with a 0.29 nanomoles per litre increase in total testosterone.
A positive association was also noted with bioavailable testosterone and sex hormone-binding globulin (SHBG), a protein that binds to these hormones and aids in their transport in the bloodstream. However, it is important to note that these findings do not imply that coffee elevates all forms of testosterone. Some inverse associations were observed, particularly regarding free testosterone and the free androgen index, a calculated measure derived from hormonal concentrations.
For women, the pattern was different; coffee consumption was linked to increased SHBG levels and lower values of free testosterone and the free androgen index, but no significant associations were found with total or bioavailable testosterone.
The Need for Further Research
“Millions of people drink coffee daily, yet we know surprisingly little about its relationship with our metabolism and hormones,” stated Luca Verroest, the lead author of the study and a doctoral researcher at the University of Oulu. “What stood out in our findings was a distinct hormonal footprint that persisted even after accounting for BMI and lifestyle factors, with several associations differing between men and women.”
Nevertheless, these results should be interpreted cautiously. The study was cross-sectional, meaning it analysed data collected at a single point in time, thereby limiting the ability to establish causality. While associations exist, it remains unclear whether coffee consumption is the driving force behind the observed differences.
Moreover, consumption was assessed through questionnaires without accounting for variables such as cup size, coffee bean variety, roast degree, or preparation methods. Hormone measurements were not taken at different time points to observe variations over time.
Regardless, this research provides a more comprehensive overview of coffee and its effects on human physiology. The beverage is now linked to variations in body composition, certain metabolites, and sex-specific hormonal profiles. Determining whether these associations translate into tangible health benefits will require further rigorous testing and extensive trials.