physiological and psychological effects of combat ration feeding during a 12-day training exercise in the tropics, The

Military Medicine, Jan 2003 by Booth, Christine K

The health and psychological effects of combat ration pack (CRP) feeding during 12 days of military training in a tropical environment were investigated. Three groups of air defence guards (ADGs) received either: freshly prepared foods (fresh group, 15 mega joule (MJ), 3,600 kcal, N = 13), full CRP (15 MJ, 3,600 kcal, N = 10), or one-half CRP (7.5 MJ, 1,800 kcal, N = 10). Underconsumption by the full CRP group resulted in CRP groups experiencing similar weight loss, protein catabolism, and immune suppression (both cell-mediated and humoral), whereas the fresh group maintained their weight and protein balance and cell-mediated immune status. CRP groups reported greater fatigue than the fresh group. All ADGs experienced poor sleep quality and declining folate and iron status. ADGs drank insufficient water to prevent dehydration. In the medium term, ADGs were able to adapt to restricted food consumption and poor sleep quality with no decrement in physical fitness or cognition.

Introduction

Generally, Australian soldiers can expect to be fed with combat ration packs (CRP) until field kitchens are established and fresh feeding can commence. However, recent experience has shown that CRPs are often the only practical means of feeding for extended periods. For example, during the initial Operation Warden deployment (in East Timor), Australian Defence Force members of the International Force, East Timor were supplied with CRP for up to 6 weeks with little or no supplemental fresh foods.

The assumption that a ration is nutritionally adequate and will sustain the soldier indefinitely is debatable. This assumption implies that a soldier will eat the entire CRP under favorable and unfavorable conditions and does not account for the increased metabolic demands associated with extreme environmental conditions and arduous physical and psychological activity. Therefore, the adequacy of the CRP can only be confirmed under realistic field conditions. A review of Australian and international field evaluations of combat rations highlights that few international studies and even fewer Australian trials have documented the effects of long-term ration pack usage.I In fact, there have been no long-term field trials of Australian Ration Packs since the 1960s.2,3

The major outcome of 3 years of deliberation by Action Group 16 of Group Human Resources and Performance of the Technical Cooperation Program is an agreement that Australia will be the lead nation for a series of detailed studies concerning CRP feeding. To this end, a nutritional study was conducted in conjunction with Exercise Northern Awakening, a RAAF exercise conducted at Royal Australian Air Force (RAAF] Base Scherger during April 1999. During the study, the average temperature and humidity mid-afternoon was 33 deg C and 73%, respectively.

The RAAF exercise included training for the second Air Field Defence Squadron in defence of the air field in the form of a 10-day patrol exercise and a 2-day hostage and evacuation drill. The study aimed to assess the nutritional adequacy of Australian CRP and a fresh-food menu for this exercise in terms of dietary, anthropometric, biochemical, physiological, and psychological measures. In particular, the suitability of a lightweight CRP was assessed.

Methods

Subjects

The experimental procedures were approved by the Australian Defence Medical Ethics Committee (Australian Defence Medical Ethics Committee protocol 134/98). Written consent was obtained from each participant after the experimental details were explained. Air field defence guards (ADGs) from RAAF Base Amberley were invited to take part in a nutrition study during Exercise Northern Awakening. Thirty-three ADGs, all men, commenced the study, and two ADGs in the fresh group failed to complete the study due to injury and personal issues. The average age of the ADGs was 22 years with a range from 18 to 32 years.

Study Design

Three treatment groups were set up to compare CRP and fresh feeding and to investigate the effects of a restricted CRP menu. Each rifle flight received a single dietary treatment, either full CRP menu (15 mega joule (MJ), 3,600 kcal, N = 10), one-half CRP menu (7.5 MJ, 1,800 kcal, Nh= 10), or freshly prepared meals (15 MJ, 3,600 kcal, N = 13, fresh group). Although random allocation of diets to ADGs within rifle flights was not possible, allocation of rifle flights to a treatment group was random. Because of the adverse effect of chicken meat on the urinary excretion of 1-methylhistidine, a marker of dietary meat intake used in this study, chicken was excluded from the three menus.4 Each menu was designed to provide a similar breakdown of macronutrients as a percentage of total energy: 54% carbohydrate, 30% fat, and 16% protein. To encourage complete consumption of the CRP, ADGs were able to customize their CRP by making food choices from an exchange menu.5 CRP items included boil-in-the bag (retort), canned, and freeze-dried main meal choices (Table I). ADGs in the fresh group received a hot breakfast meal with a ready-to-eat cereal, toast, and fruit juice, a cold meat salad with bread, fruit, and milk drink for lunch, and a hot evening meal served with pasta or rice, vegetables, and a low-fat desert. In addition they received a ration supplement containing tea, coffee, cheese, condensed milk, fruit, sugar, sports drink, candy, crisp bread, sweet biscuits, and chocolate. This provided on average: 15.1 MJ (3,600 kcal), 200 g of protein, 130 g of fat, and 510 g of carbohydrate.