Coffee intake and the vasopressin system: an epidemiological and experimental study.

Coffee is epidemiologically linked to health benefits and risks. Coffee is thought to be a diuretic. However, it can still contribute to daily fluid intake. Vasopressin is the most important physiological regulator of body fluid balance and diuresis. This study aimed to map the effects of coffee intake on vasopressin concentration. In the population-based cross-sectional Malmö Offspring Study (n = 3,270, age 18-75 years, 47% males) we performed linear regression analyses to investigate the association between coffee intake and plasma concentration of copeptin (a vasopressin surrogate marker). Coffee intake was assessed using a 4-day food record. Moreover, we compared plasma copeptin concentrations after intake of 4 dL of coffee and 10 mL of water (control) in an experimental study (n = 26, age 35-70 years, 15% males). Results showed that higher coffee intake was associated with lower copeptin concentration after adjusting for co-variables, including total fluid intake. In the coffee experiment, the acute intake of 4 dL of coffee significantly decreased copeptin concentration at all time points (every 30 min for 4 h) compared with baseline concentration. A 27% maximum reduction on average was observed within 150 min. Intake of 10 mL of water also resulted in a slight reduction of copeptin concentration within 2 h. These findings suggest that copeptin concentration is lower among individuals with high coffee intake and can be acutely decreased by coffee intake. The mechanisms behind the coffee-induced reduction in copeptin concentration may involve oral and gut reflexes, volume load, and/or specific effects of coffee compounds.