Print version

Australian Defence Force Nutritional Requirements in the 21st Century (Version 1).

• Download this publication

Abstract

This report addresses the determinants of military nutritional requirements—that is, the relevant variables that determine the types and quantities of foods necessary to support ADF training and operations—and the current state of knowledge about nutritional requirements. It also includes recommendations on nutritional standards for ADF rationing systems, and suggests areas of research that will help fill the gaps in our knowledge. Nutritional standards are recommended for fresh (i.e. in-barracks or garrison) feeding and for combat ration packs. These standards are based largely on the Nutrient Reference Values recommended by the National Health and Medical Research Council for Australia and New Zealand, but include specific Military Nutrient Reference Values for certain key nutrients.

Executive Summary

This report addresses the determinants of military nutritional requirements—that is, the relevant variables that determine the types and quantities of foods necessary to support ADF training and operations. It also examines the current state of knowledge about nutritional requirements, includes recommendations on nutritional standards for ADF rationing systems, and suggests areas of research that will help fill the gaps in our knowledge. This is the second revision (i.e. the third iteration) of Australian Defence Force Nutritional Requirements in the 21st Century. However, although the two earlier documents were ‘internal reports’, i.e. they were not published in the DSTO Report Series, they were used by the Defence Materiel Organisation (DMO) to set standards for ADF combat ration packs (CRP) and by DSTO to assess the nutritional adequacy of CRP and of fresh-feeding systems. The recent publication by the National Health and Medical Research Council (NHMRC, 2006) of Nutrient Reference Values for Australia and New Zealand provided an incentive and an opportunity to revise and update this report. It is intended to be a ‘living document’—i.e. it will be available only in electronic form and not in hard copy—so it can be updated whenever new information becomes available. The 2009 Defence White Paper (Department of Defence, 2009) imposes on the ADF a need for self-reliance, a high level of mobility, and an ability to operate in all terrains, climatic conditions and social situations. Therefore, there is a need for rationing systems (particularly ration packs) that will sustain troops during short-term, high-intensity operations (e.g. up to 72 hours) and also a need for rationing systems that will support long-term, low-intensity operations (lasting many weeks). In each case, operations could be conducted in the heat, cold and/or at altitude, in rainforest, desert or temperate regions. Physical activity levels and gender are the two major determinants of nutritional requirements of ADF members, with age, stature, climate, altitude, terrain, and individual variation playing relatively minor roles. Each of these determinants exerts its effects predominantly via an influence on energy expenditure. Females have approximately 70– 75% of the energy requirement that males have for the same activity. The only substantial purely gender-related difference in nutritional requirements is a greater need for iron by female ADF members. However, the unique requirements of adolescent ADF members should be taken into account in messes where adolescents constitute a substantial proportion of the ADF population being rationed. Adolescent ADF members have a slightly greater need than adults for energy for growth, and generally also for physical activity. Adolescents also have a significantly greater need than adults of the same gender for some micronutrients, particularly calcium (males and females), phosphorus (males and females) and iron (males only). The nutritional requirements discussed for ADF members in this document will not necessarily apply to each individual. Although the ADF population is relatively homogeneous, there will always be some variation between individuals. This variation comes from two main sources—different body size and composition, and individual genetic variation in metabolism. However, largely because requirements will vary ‘normally’ (in the statistical sense) about the mean, it is considered appropriate to base nutritional standards on the nutritional requirements of average male and average female members of the ADF. The extent of ‘over-nutrition’ (i.e. excess body fat levels) in the ADF needs to be investigated. The Australian Defence Health Status Report (published in 2000) found that 57% of ADF members were above the healthy weight range. Recommendations are made in the present report on how improvements may be made to monitoring and reporting of body fat levels and determining risk of ill-health through the addition of a simple measurement—waist circumference—to existing regular medical examinations. It appears to be a near-universal finding that troops under-eat on operations when rationing is by CRP. When nutrient intake is less than ideal, the nutritional status of a subject prior to the period of low nutrient intake itself becomes a determinant of subsequent nutritional status. There is evidence from the military scientific literature (both Australian and overseas) that young service people are entering military service with suboptimal nutritional status. The potential for this to impact adversely on health and performance can only be overcome by improvements in nutritional quality of diet during service. This implies a strong need for both availability of highly-nutritious food and guidance to ADF members on appropriate food selections to maximise nutritional status. DSTO has conducted studies to determine the energy expenditure (and therefore nutritional requirements) of (predominantly male) ADF members across a wide range of land-based, and a smaller range of sea-based military activities. These results are summarised in Tables 1 and 2 of the present report. Knowledge gaps can be filled by conducting research on ADF groups not previously studied. There is also scope for resuming the development of an expert system that will allow commanders to determine the food and water needed to sustain troops in particular operational situations. It is concluded that for the purposes of setting nutritional standards, the ADF can be divided into four population groups—adult males, adult females, adolescent males and adolescent females. Further, adult male ADF occupations can be conveniently assigned to five distinct categories of energy expenditure, while four categories apply to occupations involving adult females and adolescents. The highest category (Category 5) is believed to be a special case, applying largely to males attempting selection to the Special Air Service Regiment. Therefore, only categories 1–4 are regarded as being of practical significance to the vast majority of ADF rationing. However, further studies on the energy expenditures associated with SF training and operations are needed to confirm or alter this belief. Also, it is suggested that during a period of re-feeding following sustained under-consumption (e.g. when troops have been fed with combat ration packs for more than two weeks while engaging in very vigorous physical activities), Category 5 entitlements are appropriate for the period of re-feeding. Although there is a reasonable correlation between the defined categories of ADF activity levels and those of the NHMRC (2006), they do not correspond exactly. Consequently, it is recommended that DSTO attempt to add a category of energy expenditure (perhaps designated ‘extreme activity’) to the six existing NHMRC physical activity levels. Nutritional quality of the diet of ADF members is critical in ensuring that optimal performance can be maintained as long as possible. This quality is in terms of macronutrients (protein, fat and carbohydrate), micronutrients (vitamins, minerals and trace elements) and dietary fibre. Carbohydrate is considered to be the most important macronutrient for vigorous physical activity, with fat being of value mainly for acceptability. The important role played by protein in recovery from vigorous physical activity has been recognised only relatively recently. It is recommended that the standard for protein be set at 15–20% of total energy for situations involving light physical activity (Category 1), with the range of percentage contributions decreasing linearly as energy expenditure increases (from 14–19% for Category 2 to 11–14% for Category 5). Conversely, the percentage of energy derived from carbohydrate should increase linearly with increasing physical activity from a range of 50–55% (Category 1) to 58–63% (Category 5), at the expense of fat (decreasing linearly from 27–35% (Category 1) to 23–31% (Category 5). The recommended ratios of protein to fat to carbohydrate (P:F:C ratios) are shown in Table 4. As indicated in a footnote to Table 4, the only situation in which it is recommended that carbohydrate should provide more than 63% of energy is when operations are conducted at high altitude—here it is recommended that the P:F:C ratio should be approximately 15:20:65 respectively. There is preliminary evidence that not only the quantity, but also the quality of carbohydrate may impact on both performance and health. Further research is warranted on the potential to enhance nutritional status by varying the glycaemic index and increasing resistant starch in rations (particularly in combat ration packs). There is also scope for conducting research on the impact of combining protein with carbohydrate to enhance recovery from vigorous physical activity. The previous two iterations of this report included Recommended Military Dietary Intakes (RMDIs) for all nutrients that had been assigned Recommended Dietary Intakes (RDIs) in 1991 by the NHMRC. The RMDIs corresponded very closely to the RDIs. In 2006 the NHMRC published Nutrient Reference Values (NRVs) to apply to the population of Australia and New Zealand. These differ, often substantially, from the 1991 recommendations. It is recommended that the RDIs (or Adequate Intake if an RDI has not been established) of the NHMRC (2006) be adopted as Military Recommended Dietary Intakes (MRDIs) for all nutrients other than thiamin, riboflavin, niacin, vitamin B6, protein and sodium, and also for total energy. The reasons for these exceptions are detailed in the body of this report. It is also recommended that MRDIs be defined for carbohydrate, even though NRVs were not published by the NHMRC for carbohydrate. It is recommended that military-specific Estimated Average Requirements (MEAR) be calculated for the Bgroup vitamins thiamin, riboflavin, niacin and vitamin B6 as 70% of the respective MRDIs. Finally, it is argued that nutritional standards should take into account age (adult versus adolescent), gender and activity level. Table 5 shows the MRDIs for adult males for five categories of physical activity; Tables 6–8 show the MRDIs for the adult females, adolescent males and adolescent females of the ADF for four categories of activity. Nutritional standards are recommended for general purpose (i.e. not mission-specific) CRP. These are based on Category 3 requirements for energy (~16 MJ), protein and carbohydrate for adult males and the MRDI that constitutes the ‘worst case’ situation for each micronutrient (i.e. the sub-group that has the greatest requirement for each specific micronutrient) for ADF members working at Category 3 That is, the nutritional requirements of practically all ADF members working at Category 3 will be met by the basic ration pack if it is eaten in its entirety. Table 9 details the recommended nutritional criteria for general purpose ration packs. Further, it is recommended that fortification to three times the MRDI should occur for four key vitamins—thiamin, riboflavin, vitamin B6 and vitamin C—to counteract storage losses and the discarding of ration pack items. It is also recommended that more research be conducted into vitamin stability during storage of ration packs, and on how bioavailability of micronutrients from combat ration packs affects nutritional status of ADF members. It is recommended that a small range of mission-specific ration packs be developed; that consideration be given to adopting a modular, just-in-time process for procuring, packing and distributing CRP; and that investigation be conducted into the need for, and most appropriate form of a group-feeding pack. Recommendations are provided on how entitlements to fresh rations should be determined. Tables 5–8 show the MRDIs that apply for homogeneous groups of ADF members (i.e. all members are of the same gender and age group—adult or adolescent). For a mixed ADF population (a mixture of genders and age groups) the entitlements to energy and macronutrients for fresh feeding should be based on the number to be fed and the MRDIs that apply to the ‘worst case’ situation (i.e. the sub-group that has the greatest requirement for each specific nutrient). Table 10a shows these recommended entitlements. Appendix B provides an example of how the entitlements to total energy can be determined for a mixed ADF population to be fed freshly-cooked food at a mess. In designing ration scales for fresh feeding, it is recommended that a basic scale be devised based on the MRDIs for energy, protein and carbohydrate for adolescent males working at Category 1. For the remaining nutrients, the MRDI that applies to Category 4 physical work output for the population sub-group that constitutes the ‘worst case’ situation should apply. Table 10c shows the recommended nutritional basis of the basic fresh-feeding scale. Allowance should also be made for inevitable food discarding. It is suggested that this allowance be 15%—i.e. food availability should be 15% above the estimated requirement. To feed troops working above Category 1, it is recommended that between-meal snacks be devised in modular form, with each module providing 1–2 MJ. Dietary modelling should be conducted to determine the ability of ‘real world’ diets based on these entitlements to meet the MEARs of ADF members. Table 10b shows the nutritional criteria for this dietary modelling for mixed population groups of ADF members. Table 10d shows the nutritional criteria for modelling the adequacy of the basic ration scale (Category 1, mixed population). In assessing the nutritional adequacy of intake of ADF groups it is also the MEARs that apply. Table 10b applies in relation to assessing the adequacy of intake for mixed population groups; Tables 11–14 apply to the four categories of homogeneous groups of ADF members. When determining the adequacy of nutritional intake of an individual ADF member, it is appropriate to use the MRDIs applicable to that individual’s population group and activity category (Tables 5–8 apply). The recommended entitlements in this report are also considered to be an appropriate basis for the development of military core food groups and a military guide to healthy eating. It is also suggested that the nutritional entitlements supporting ‘hot-boxed meals’ (used for fresh feeding in the field) should be based on the appropriate work category (3 or above) for adult male ADF members. The implications of under-consumption in the field, specifically when feeding is by CRP, are addressed. The origins of ‘negative energy balance’, how this affects military performance, and steps that may be taken in an attempt to overcome any perceived problems are critical factors affecting nutritional status of ADF members. It is concluded that previously well-nourished troops should suffer no decrement to performance for at least 16 days when rationing is solely by CRP. It is also concluded that more research is needed in this area. Following an extended period of negative energy balance, it may be appropriate to aim for a recovery period equal to about half the period of negative energy balance. Until further information is available, it is considered prudent to attempt to limit the rate at which recovery is attained to a maximum of ~8 MJ per day. That is, the tentative recommendation is that the excess of intake over expenditure during the recovery period should be no more than 8 MJ per day. It may also be appropriate to seek advice from military Medical Officers on how recovery feeding can be safely conducted if troops have undergone an extensive period of severe under-consumption.

Back to the top