title: Nitrogen balance in older individuals in energy balance depends on timing of protein intake.
abstract: 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.
authors.affiliation: Department of Health and Exercise Science, Colorado State University, Fort Collins, CO 80523-1582, USA.
authors.forename: Leora Y
authors.initials: LY
authors.lastname: Jordan
authors.forename: Edward L
authors.initials: EL
authors.lastname: Melanson
authors.forename: Christopher L
authors.initials: CL
authors.lastname: Melby
authors.forename: Matthew S
authors.initials: MS
authors.lastname: Hickey
authors.forename: Benjamin F
authors.initials: BF
authors.lastname: Miller
mesh_terms: D000368:Aged; D018592:Cross-Over Studies; D004040:Dietary Carbohydrates / Q000494:pharmacology; D004044:Dietary Proteins / Q000494:pharmacology*; D004734:Energy Metabolism / Q000502:physiology*; D015444:Exercise / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009584:Nitrogen / Q000378:metabolism*; D009751:Nutritional Requirements; D013997:Time Factors
chemical_list: D004040:Dietary Carbohydrates; D004044:Dietary Proteins; D009584:Nitrogen