Soft drink consumption during and following exercise in the heat elevates biomarkers of acute kidney injury

The purpose of this study was to test the hypothesis that consuming a soft drink (i.e., a high-fructose, caffeinated beverage) during and following exercise in the heat elevates biomarkers of acute kidney injury (AKI) in humans. Twelve healthy adults drank 2 liters of an assigned beverage during 4 h of exercise in the heat 35.1 (0.1)°C, 61 (5)% relative humidity in counterbalanced soft drink and water trials, and ≥1 liter of the same beverage after leaving the laboratory. Stage 1 AKI (i.e., increased serum creatinine ≥0.30 mg/dl) was detected at postexercise in 75% of participants in the Soft Drink trial compared with 8% in Water trial ( P = 0.02). Furthermore, urinary neutrophil gelatinase-associated lipocalin (NGAL), a biomarker of AKI, was higher during an overnight collection period after the Soft Drink trial compared with Water in both absolute concentration 6 (4) ng/dl vs. 5 (4) ng/dl, P < 0.04 and after correcting for urine flow rate 6 (7) (ng/dl)/(ml/min) vs. 4 (4) (ng/dl)/(ml/min), P = 0.03. Changes in serum uric acid from preexercise were greater in the Soft Drink trial than the Water trial at postexercise ( P < 0.01) and 24 h ( P = 0.05). There were greater increases from preexercise in serum copeptin, a stable marker of vasopressin, at postexercise in the Soft Drink trial ( P < 0.02) than the Water trial. These findings indicate that consuming a soft drink during and following exercise in the heat induces AKI, likely via vasopressin-mediated mechanisms.