Higher habitual coffee consumption was associated with a distinct metabolic and hormonal profile, including lower concentrations of branched-chain amino acids (BCAAs), which have been linked to insulin resistance and future type 2 diabetes risk, according to a population-based study of middle-aged adults.
Researchers analyzed data from 2264 participants in the Northern Finland Birth Cohort 1966, all aged 46 years. The cross-sectional study, published in The European Journal of Nutrition, combined reported coffee consumption with clinical measurements, hormone testing, and nuclear magnetic resonance metabolomics. The metabolomics platform quantified 164 lipid and metabolite measures.
Greater coffee consumption was associated with lower levels of circulating BCAAs, including leucine in both sexes and isoleucine and valine in men. Although the correlations were generally small, several remained statistically significant after correction for multiple comparisons. Elevated circulating BCAAs have previously been associated with insulin resistance and can precede development of type 2 diabetes, making the finding potentially relevant to efforts to identify metabolic risk before overt disease develops.
The findings also suggest that interpretation of metabolic biomarkers may need to account for sex. Among men, greater coffee consumption was associated with lower fasting insulin and measures of insulin resistance and with higher insulin sensitivity. Hormonal testing showed higher total and bioavailable testosterone and sex hormone–binding globulin (SHBG), but lower free testosterone and free androgen index with increasing coffee intake. Among women, associations were more limited, with higher SHBG and lower free testosterone and free androgen index.
Higher coffee intake was additionally associated with lower total and visceral fat and greater skeletal muscle mass despite similar body mass index across consumption groups.
Lead researcher Luca Verroest said, "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."
The study highlights habitual coffee intake as a potential contributor to variation in metabolic and endocrine biomarker profiles. However, the findings do not establish that coffee causes these changes. Coffee intake was self-reported, biomarkers were measured at a single time point, and the Finnish cohort may not represent populations with different coffee-drinking patterns. Longitudinal and intervention studies will be needed before the observed signatures can inform individual diagnostic or risk-assessment decisions.
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