May 9, 2025, 12:36 pm | Read time: 3 minutes
The daily cup of coffee not only provides a boost of energy but also positively affects insulin levels. One gender seems to benefit particularly from this.
A day without coffee? Unthinkable for many. Fortunately, there are numerous health reasons to maintain the ritual. Previous studies have already found that regular coffee consumption can reduce the risk of type 2 diabetes. But is there a difference between men and women regarding the impact of coffee on insulin levels? Korean researchers have explored this question and discovered remarkable results, now published in the journal “Nutrients.”1
Overview
How the Study on Insulin and Coffee Was Conducted
The coffee study included 7,453 adults aged 19 to 64. Of these, 4,155 were women and 3,298 were men. Participants provided additional information via a questionnaire, including
- gender
- how many cups of coffee they drank in the last 24 hours and in what form (with/without sugar and milk)
- lifestyle, weight, alcohol consumption, education level, physical activity, and marital status
Additionally, researchers measured various markers of the participants’ glucose metabolism, including
- fasting blood sugar
- fasting insulin levels
- HOMA-IR (Homeostasis Model Assessment of Insulin Resistance): A measure of insulin resistance. High values are associated with an increased risk of hypertension and diabetes.
- HOMA-β (Homeostasis Model Assessment of β-cell function): A measure of the function of insulin-producing beta cells. High values may indicate the onset of insulin resistance.
Results of the Analysis
The researchers compared the completed questionnaires with the measured values. It was found that consuming two cups of coffee per day, without milk and sugar, reduces the risk of elevated HOMA-IR values by an average of 23 percent. Thus, a relatively small amount of coffee is sufficient to regulate insulin levels and improve glucose metabolism. Coffee consumption, however, had no interpretable effect on HOMA-β values. The positive effects of coffee on glucose metabolism are, therefore, likely due to improved insulin action.
Coffee Affects Insulin Differently in Men and Women
The evaluation was strictly separated by gender. It was found that women apparently benefit greatly from regular coffee consumption. Two to three cups of black coffee (without milk and sugar) reduced their risk of high HOMA-IR values by 36 percent. With more cups, the effect seemed to increase even further—however, the group of heavy drinkers was too small for a definitive result. In men, on the other hand, the consumption of black coffee showed no significant effect on glucose metabolism in the study.
Explaining the Gender Differences
The researchers suspect that different metabolic processes in men and women influence how they each react to coffee or caffeine. Different hormone levels (estrogen) could play a role in insulin sensitivity. Additionally, the generally healthier lifestyle of women may contribute. The researchers now hope that future studies will clarify the open questions.
The Effect of Black Coffee on Insulin Levels
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Strengths and Weaknesses of the Study
Coffee apparently has a regulatory influence on insulin levels—more pronounced in women than in men. Given the large sample size with many participants, the results can be considered representative. However, it remains an observational study, relying on self-reported data or participants’ memories of their coffee consumption in the 24 hours preceding the survey. The study could not demonstrate a long-term effect of black coffee. Additionally, it cannot conclusively determine how exactly coffee affects glucose metabolism and insulin levels—only that a connection exists.