Carbohydrate hastens hypervolemia achieved through ingestion of aqueous sodium solution in resting euhydrated humans

Ingesting beverages containing a high concentration of sodium under euhydrated conditions induces hypervolemia. Because carbohydrate can enhance interstitial fluid absorption via the sodium–glucose cotransporter and insulin-dependent renal sodium reabsorption, adding carbohydrate to high-sodium beverages may augment the hypervolemic response. To test this hypothesis, we had nine healthy young males ingest 1087 ± 82 mL (16–17 mL per kg body weight) of water or aqueous solution containing 0.7% NaCl, 0.7% NaCl + 6% dextrin, 0.9% NaCl, or 0.9% NaCl + 6% dextrin under euhydrated conditions. Each drink was divided into six equal volumes and ingested at 10-min intervals. During each trial, participants remained resting for 150 min. Measurements were made at baseline and every 30 min thereafter. Plasma osmolality decreased with water ingestion (P ≤ 0.023), which increased urine volume such that there was no elevation in plasma volume from baseline (P ≥ 0.059). The reduction in plasma osmolality did not occur with ingestion of solution containing 0.7% or 0.9% NaCl (P ≥ 0.051). Consequently, urine volume was 176–288 mL smaller than after water ingestion and resulted in plasma volume expansion at 60 min and later times (P ≤ 0.042). In addition, net fluid balance was 211–329 mL greater than after water ingestion (P ≤ 0.028). Adding 6% dextrin to 0.7% or 0.9% NaCl solution resulted in plasma volume expansion within as little as 30 min (P ≤ 0.026), though the magnitudes of the increases in plasma volume were unaffected (P ≥ 0.148). Dextrin mediates an earlier hypervolemic response associated with ingestion of high-sodium solution in resting euhydrated young men. (247/250 words)