Improved Postexercise Rehydration With a Milk Permeate-Based Sports Drink

This study evaluated the rehydration efficacy of a commercially available milk permeate-containing sports drink with high osmolality (MPSD) compared with a traditional sports drink (TSD), a high-potassium sports drink (HKSD), and water (W). Twelve young, healthy adults (four women) underwent a 2-hr exercise-induced dehydration protocol in the heat (29.9 °C ± 1.5 °C) until losing 2% of body weight, followed by a 4-hr rehydration period. Participants consumed on four separate occasions one of the following beverages: (a) TSD (Na⁺: 20 mmol/L, K⁺: 3.6 mmol/L, osmolality: 385 mmol/kg); (b) HKSD (Na⁺: 3.6 mmol/L, K⁺: 37.9 mmol/L, osmolality: 364 mmol/kg); (c) MPSD (Na⁺: 21 mmol/L, K⁺: 28.7 mmol/L, osmolality: 576 mmol/kg); or (d) plain water (W). Fluids (150% of body weight loss) were administered in four doses every 15 min during the first hour. Whole-body net fluid balance remained negative, but MPSD resulted in significantly higher net fluid balance at 180 min (−0.38% ± 0.3%) and 240 min (−0.66% ± 0.3%) than in other trials (p < .05). MPSD also led to lower cumulative urine volume (1,268 ± 173 ml) than HKSD (1,796 ± 459 ml), TSD (1,493 ± 211 ml), and W (1,565 ± 501 ml; p < .05). Osmotic excretion in MPSD was significantly higher than in all trials at 120, 180, and 240 min (p < .05), and free water clearance was lower at 180 and 240 min (p < .05). TSD promoted greater plasma volume restoration (1.5% ± 5%) than MPSD (−3.7% ± 6.5%) and HKSD (−5.5% ± 7.8%) at 60 min (p < .05). A milk permeate-based sports drink is more effective for postexercise rehydration than TSD, HKSD, and water when consumed at 150% of the body weight lost.