Nitrogen balance in older individuals in energy balance depends on timing of protein intake

J Gerontol A Biol Sci Med Sci. 2010 Oct;65(10):1068-76. doi: 10.1093/gerona/glq123. Epub 2010 Jul 9.


To explore whether nitrogen retention can differ on an isonitrogenous diet by changing when protein is consumed, we performed a short-term study in older individuals (64.5 ± 2.0 years) performing daily exercise while in energy balance. Participants consumed an isonitrogenous-isocaloric diet with the timing of a protein or carbohydrate beverage after exercise (protein after exercise [PRO], carbohydrate after exercise [CHO]) versus earlier in the day. Three-day mean energy balance (PRO: 202 ± 36 kcal and CHO: 191 ± 44 kcal; p = .68) did not differ between trials, but 3-day mean nitrogen balance was significantly more positive in the PRO (1.2 ± 0.32 g N) trial than the CHO trial (0.8 ± 0.45 g N; p < .05). Older individuals were better able to maintain nitrogen balance by simply changing when a portion of an identical amount of daily protein was consumed.

Publication types

  • Randomized Controlled Trial
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Cross-Over Studies
  • Dietary Carbohydrates / pharmacology
  • Dietary Proteins / pharmacology*
  • Energy Metabolism / physiology*
  • Exercise / physiology
  • Female
  • Humans
  • Male
  • Middle Aged
  • Nitrogen / metabolism*
  • Nutritional Requirements
  • Time Factors


  • Dietary Carbohydrates
  • Dietary Proteins
  • Nitrogen