title: Effects of Supplemental Energy on Protein Balance during 4-d Arctic Military Training.
abstract: Soldiers often experience negative energy balance during military operations that diminish whole-body protein retention, even when dietary protein is consumed within recommended levels (1.5-2.0 g·kg·d).
  
  
  
  The objective of this study is to determine whether providing supplemental nutrition spares whole-body protein by attenuating the level of negative energy balance induced by military training and to assess whether protein balance is differentially influenced by the macronutrient source.
  
  
  
  Soldiers participating in 4-d arctic military training (AMT) (51-km ski march) were randomized to receive three combat rations (CON) (n = 18), three combat rations plus four 250-kcal protein-based bars (PRO, 20 g protein) (n = 28), or three combat rations plus four 250-kcal carbohydrate-based bars daily (CHO, 48 g carbohydrate) (n = 27). Energy expenditure (D2O) and energy intake were measured daily. Nitrogen balance (NBAL) and protein turnover were determined at baseline (BL) and day 3 of AMT using 24-h urine and [N]-glycine.
  
  
  
  Protein and carbohydrate intakes were highest (P < 0.05) for PRO (mean ± SD, 2.0 ± 0.3 g·kg·d) and CHO (5.8 ± 1.3 g·kg·d), but only CHO increased (P < 0.05) energy intake above CON. Energy expenditure (6155 ± 515 kcal·d), energy balance (-3313 ± 776 kcal·d), net protein balance (NET) (-0.24 ± 0.60 g·d), and NBAL (-68.5 ± 94.6 mg·kg·d) during AMT were similar between groups. In the combined cohort, energy intake was associated (P < 0.05) with NET (r = 0.56) and NBAL (r = 0.69), and soldiers with the highest energy intake (3723 ± 359 kcal·d, 2.11 ± 0.45 g protein·kg·d, 6.654 ± 1.16 g carbohydrate·kg·d) achieved net protein balance and NBAL during AMT.
  
  
  
  These data reinforce the importance of consuming sufficient energy during periods of high energy expenditure to mitigate the consequences of negative energy balance and attenuate whole-body protein loss.
authors.affiliation: 1Military Nutrition Division, US Army Research Institute of Environmental Medicine, Natick, MA; 2Norwegian Defence Research Establishment, Kjeller, NORWAY; and 3Thermal Mountain and Medicine Division, US Army Research Institute of Environmental Medicine, Natick, MA.
authors.forename: Lee M
authors.initials: LM
authors.lastname: Margolis
authors.forename: Nancy E
authors.initials: NE
authors.lastname: Murphy
authors.forename: Svein
authors.initials: S
authors.lastname: Martini
authors.forename: Yngvar
authors.initials: Y
authors.lastname: Gundersen
authors.forename: John W
authors.initials: JW
authors.lastname: Castellani
authors.forename: J Philip
authors.initials: JP
authors.lastname: Karl
authors.forename: Christopher T
authors.initials: CT
authors.lastname: Carrigan
authors.forename: Hilde-Kristin
authors.initials: HK
authors.lastname: Teien
authors.forename: Elisabeth-Henie
authors.initials: EH
authors.lastname: Madslien
authors.forename: Scott J
authors.initials: SJ
authors.lastname: Montain
authors.forename: Stefan M
authors.initials: SM
authors.lastname: Pasiakos
mesh_terms: D004040:Dietary Carbohydrates / Q000008:administration & dosage; D004044:Dietary Proteins / Q000008:administration & dosage*; D019587:Dietary Supplements; D002149:Energy Intake; D004734:Energy Metabolism; D015444:Exercise; D005260:Female; D006801:Humans; D008297:Male; D008889:Military Personnel; D064797:Physical Conditioning, Human; D055815:Young Adult
chemical_list: D004040:Dietary Carbohydrates; D004044:Dietary Proteins