Effect of Preexercise Soup Ingestion on Water Intake and Fluid Balance During Exercise in the Heat

Purpose: To determine whether chicken noodle soup before exercise increases ad libitum water intake, fluid balance, and physical and cognitive performance compared with water. Methods: Nine trained men (age 25 +/- 3 yr, VO2peak 54.2 +/- 5.1 ml . kg(-1) . min(-1); M +/- SD) performed cycle exercise in the heat (wet bulb globe temperature = 25.9 +/- 0.4 degrees C) for 90 mm at 50% VO2peak, 45 min after ingesting 355 ml of either commercially available bottled water (WATER) or chicken noodle soup (SOUP). The same bottled water was allowed ad libitum throughout both trials. Participants then completed a time trial to finish a given amount of work (10 min at 90% VO2peak; n = 8). Cognitive performance was evaluated by the Stroop color-word task before, every 30 min during, and immediately after the time trial. Results: Ad libitum water intake throughout steady-state exercise was greater in SOUP than with WATER (1,435 +/- 593 vs. 1,163 +/- 427 g, respectively; p < .03). Total urine volume was similar in both trials (p = .13), resulting in a trend for greater water retention in SOUP than in WATER (87.7% +/- 7.6% vs. 74.9% +/- 21.7%, respectively; p = .09), possibly due to a change in free water clearance (-0.32 +/- 1.22 vs. 0.51 +/- 1.06 ml/min, respectively; p = .07). Fluid balance tended to be improved with SOUP (-106 +/- 603 vs. -478 +/- 594 g, p = .05). Likewise, change in plasma volume tended to be reduced in SOUP compared with WATER (p = .06). Only mild dehydration was achieved (<1%), and physical performance was not different between treatments (p = .77). The number of errors in the Stroop color-word task was lower in SOUP throughout the entire trial (treatment effect; p = .04). Conclusion: SOUP before exercise increased ad libitum water intake and may alter kidney function.