Effect of sodium in a rehydration beverage when consumed as a fluid or meal

To investigate the impact of fluid compositionon rehydration effectiveness, 30 subjects (15 men and 15 women) werestudied during 2 h of rehydration after a 2.5% body weight loss. In a randomized crossover design, subjects rehydrated with water(H₂O), chicken broth (CB: 109.5 mmol/l Na, 25.3 mmol/l K), a carbohydrate-electrolyte drink (CE: 16.0 mmol/l Na, 3.3 mmol/l K), and chicken noodle soup (Soup: 333.8 mmol/lNa, 13.7 mmol/l K). Subjects ingested 175 ml at the start ofrehydration and 20 min later; H₂Owas given every 20 min thereafter for a total volume equal to bodyweight loss during dehydration. At the end of the rehydration period, plasma volume was not significantly different from predehydration values in the CB (1.6 ± 1.1%) and Soup (1.4 ± 0.9%) trials. In contrast, plasma volume remained significantly(P < 0.01) below predehydrationvalues in the H₂O (5.6 ± 1.1%) and CE (4.2 ± 1.0%) trials after therehydration period. Urine volume was greater in the CE (310 ± 30 ml) than in the CB (188 ± 20 ml) trial. Urine osmolality was higher in the CB and Soup trials than in the CE trial.Urinary sodium concentration was higher in the Soup and CB trials thanin the CE and H₂O trials. Theseresults provide evidence that the inclusion of sodium in rehydrationbeverages, as well as consumption of a sodium-containing liquid meal,increases fluid retention and improves plasma volume restoration.