Effect of milk protein addition to a carbohydrate-electrolyte rehydration solution ingested after exercise in the heat

Br J Nutr. 2011 Feb;105(3):393-9. doi: 10.1017/S0007114510003545. Epub 2010 Sep 28.


The present study examined the effects of milk protein on rehydration after exercise in the heat, via the comparison of energy- and electrolyte content-matched carbohydrate and carbohydrate-milk protein solutions. Eight male subjects lost 1·9 (SD 0·2) % of their body mass by intermittent exercise in the heat and rehydrated with 150% of their body mass loss with either a 65 g/l carbohydrate solution (trial C) or a 40 g/l carbohydrate, 25 g/l milk protein solution (trial CP). Urine samples were collected before and after exercise and for 4 h after rehydration. Total cumulative urine output after rehydration was greater for trial C (1212 (SD 310) ml) than for trial CP (931 (SD 254) ml) (P < 0·05), and total fluid retention over the study was greater after ingestion of drink CP (55 (SD 12) %) than that after ingestion of drink C (43 (SD 15) %) (P < 0·05). At the end of the study period, whole body net fluid balance (P < 0·05) was less negative for trial CP (-0·26 (SD 0·27) litres) than for trial C (-0·52 (SD 0·30) litres), and although net negative for both the trials, it was only significantly negative after ingestion of drink C (P < 0·05). The results of the present study suggest that when matched for energy density and fat content, as well as for Na and K concentration, and when ingested after exercise-induced dehydration, a carbohydrate-milk protein solution is better retained than a carbohydrate solution. These results suggest that gram-for-gram, milk protein is more effective at augmenting fluid retention than carbohydrate.

Publication types

  • Comparative Study
  • Randomized Controlled Trial

MeSH terms

  • Body Weight
  • Carbohydrates / administration & dosage
  • Carbohydrates / urine
  • Cross-Over Studies
  • Double-Blind Method
  • Electrolytes / administration & dosage
  • Energy Metabolism / physiology
  • Exercise / physiology*
  • Hot Temperature*
  • Humans
  • Male
  • Milk Proteins / administration & dosage
  • Milk Proteins / pharmacology*
  • Rehydration Solutions / administration & dosage
  • Rehydration Solutions / pharmacology*
  • Surveys and Questionnaires
  • Young Adult


  • Carbohydrates
  • Electrolytes
  • Milk Proteins
  • Rehydration Solutions