Effects of supplemental energy on protein balance during 4-d arctic military training

• Autores: Lee M. Margolis, Nancy Murphy, Svein Martini
• Localización: Medicine & Science in Sports & exercise: Official Journal of the American College of Sports Medicine, ISSN 0195-9131, Vol. 48, Nº. 8, 2016, págs. 1604-1612
• Idioma: inglés
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• Resumen

  • 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−1·d−1).

    Purpose: 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.

    Methods: 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 (D218O) 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 [15N]-glycine.

    Results: Protein and carbohydrate intakes were highest (P < 0.05) for PRO (mean ± SD, 2.0 ± 0.3 g·kg−1·d−1) and CHO (5.8 ± 1.3 g·kg−1·d−1), but only CHO increased (P < 0.05) energy intake above CON. Energy expenditure (6155 ± 515 kcal·d−1), energy balance (−3313 ± 776 kcal·d−1), net protein balance (NET) (−0.24 ± 0.60 g·d−1), and NBAL (−68.5 ± 94.6 mg·kg−1·d−1) 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−1, 2.11 ± 0.45 g protein·kg−1·d−1, 6.654 ± 1.16 g carbohydrate·kg−1·d−1) achieved net protein balance and NBAL during AMT.

    Conclusion: 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.