Apparently healthy young black adults report lower total fluid intake and exhibit higher plasma copeptin than young White adults

Underhydration is associated with higher plasma copeptin concentration ([copeptin]), an arginine vasopressin surrogate associated with multiple chronic diseases. Middle-aged and older Black individuals are more likely to be underhydrated and exhibit higher [copeptin] than White individuals. However, limited data exists on racial differences in [copeptin] in young adults. Therefore, we tested the hypothesis that apparently healthy young Black adults would report lower fluid intake and exhibit higher plasma [copeptin] than young White adults. Participants (n = 86; sex: 40F/46M; race: White n = 48, Black n = 38; age: 21$\pm$2 years, BMI: 25$\pm$4 kg/m²) completed 3-day food and fluid diaries. We operationalized beverages into 8 categories (water, sugar-sweetened beverages, milk/non-dairy alternatives, juice, nonaloric beverages (eg, diet drinks), coffee or tea (noncaloric), coffee or tea (caloric), and alcohol) and measured plasma [copeptin]. We assessed racial differences in fluid intake and [copeptin] and also examined relations between race, fluid intake, and [copeptin] via regression and correlation analyses. Compared with White adults, Black adults consumed less total fluid (64.0[31.3] vs. 89.7[53.6] oz), water, alcohol, and coffee/tea (noncaloric and caloric) but more juice (ps < .05). Black participants exhibited higher plasma [copeptin] (6.38[4.83] vs. 4.45[2.92] pmol/L, P = .021). In the whole cohort, plasma [copeptin] was negatively correlated with water intake ($\rho$= -0.249, P = .021). However, racial differences in [copeptin] were attenuated by 27% when accounting for total fluid intake. Black young adults reported lower fluid intake and exhibited higher plasma [copeptin] than White young adults. Interventions are needed to address racial disparities in hydration practices, potentially attenuating racial differences in [copeptin] and related health disparities.