Nutrition For Military Fitness

Introduction

Few people would be aware that one of the more significant recent applications of science and technology to military operations was the invention of food canning. Nicholas Appert - a French inventor of the early 19^th Century - was awarded a substantial prize by Napoleon Bonaparte for inventing the canning process. This is because the availability of canned food allowed the French Army to march long distances, carrying their own food, rather than having to rely on finding food along the way. One result of this was greater mobility, often allowing Napoleon’s Army to reach the battlefield ahead of the enemy, engage in surprise attacks and to be frequently in better physical condition than the enemy. Although it does not command the same headlines as the acquisition of military platforms such as Collins Class submarines, FA-18 Hornet fighters or new tanks, research and development (R&D) into food and nutrition is still considered to be vital today in helping to ‘bring out the best’ in Australian Defence Force (ADF) members. Of the major focus areas that are being subjected to intense scientific R&D - lethality, sustainability, mobility - the potential for beneficial impact from the application of new knowledge in food science is greatest in the area of sustainability of operations.

All Australian R&D on military aspects of food science is conducted by the Defence Science and Technology Organisation (DSTO) at its Defence Nutrition Research Centre (DNRC). This is a small laboratory tucked away among the green and lush pastures of rural northern Tasmania. DNRC is a laboratory of DSTO’s Combatant Protection and Nutrition Branch (CPNB). DNRC exists to determine the nutritional requirements of members of the ADF and to ensure that ADF feeding systems keep our soldiers, sailors and airmen literally ‘fighting fit’.

Determining and meeting nutritional requirements

Energy expenditure studies - Army

Using a state-of-the-art technique (based on the stable isotopes deuterium and oxygen-18), we have determined the energy expended by soldiers across a wide range of military activities. Because females are not permitted in direct combat positions such as infantry, these studies involved mainly male soldiers. Energy expenditure levels varied from a mean of 12 megajoules (MJ) per man per day for sedentary soldiers (engaged in a clerical course) to 28 MJ/day for soldiers attempting selection to the Special Air Service Regiment (SASR). Soldiers engaged in typical field exercises had mean expenditure of approximately 15 MJ/day; Army recruits expended ~16 MJ/day; while training for jungle warfare led to a mean daily expenditure of ~19 MJ. The energy cost of parachute training was surprisingly high; at nearly 17 MJ/day it was greater than the energy expended by Army recruits despite a seemingly lower physical workload on the part of the parachutists. We speculated that the stress of taking part in a potentially life-threatening activity may have led to increased metabolic rate and hence to greater energy expenditure.

Meeting demonstrated nutritional needs

From these results we categorised military activities into five levels according to energy expenditure. The results were also used to determine ‘Recommended Military Dietary Intakes’ (RMDI). The RMDI are the levels of energy and essential nutrients that are recommended for each of the five categories of military activities. Four tables of RMDI were determined, one for each of the following groups of ADF members: Servicemen, Servicewomen, Adolescent (16-18 years) Servicemen, and Adolescent (16-18 years) Servicewomen. Table 1 shows representative military activities and the RMDI for energy for two of the groups (Servicemen and Servicewomen) for each of the five categories.

In addition to total energy and essential nutrients, the mix of protein, fat and carbohydrate in the soldier's diet is important in ensuring that nutritional status promotes optimal military performance. Because carbohydrate is the preferred fuel for muscular work, soldiers' rations should be high in carbohydrate and relatively low in fat. However, this must be balanced against the requirement to minimise weight and bulk of rations, particularly in light of Australia's continuing emphasis on land operations involving foot soldiers carrying heavy loads. The Army’s soldier modernisation program (Project 'Wundurra' - an Aboriginal word for ‘warrior’) also has the potential to impact on soldier mobility (another focus area). Soldiers in the 'enhanced' condition were each carrying more than 40 kg of equipment at the 1998 Soldier Combat System Evaluation Study (98SCSES) which evaluated potential enhancements such as combat body armour, thermal weapon sights, GPS navigation and night vision goggles.

As a compromise between the conflicting requirements of nutrition and load carriage, we recommend that carbohydrate in ration packs provide in the range 56-59% of total energy, with no more than 29% of energy being derived from fat. These percentages contrast with the current average Australian civilian intakes of ~33% of energy from fat and ~50% from carbohydrate.

New generation ration packs are being designed that are nutrient- and energy-dense, provide 15 MJ of energy per ADF member per day, contain light-weight packaging, and provide adequate nutrients to meet the nutritional requirements of nearly all soldiers (regardless of gender) engaged in typical field operations. Thus for example, while the requirement for energy is set at 15 MJ (based on the energy expenditure of male soldiers), the recommendation for iron is 16 mg (the upper level of the RMDI for females). This is despite the RMDI for iron for males being only 7 mg. Table 2 shows the contents of one menu (from a total of five) of the recently introduced Combat Ration (Five Man). This pack provides 15 MJ per person per day and meets (or exceeds) the RMDI for all essential nutrients.

We also recommend that the freshly cooked food provided to ADF members in barracks, and (when the operational situation permits) in the field, be relatively low in fat and high in carbohydrate. The draft ADF Catering Manual (ADF CATMAN - currently being written by the ADF Catering Section) stresses the importance of having reduced fat alternative foods available. Examples include low-fat and reduced-fat milk as alternatives to full-cream milk, a variety of breakfast cereals (both low and high fibre), salads (with self-serve dressings), a variety of fresh fruit, and the use of low-fat cooking methods.

Future studies

Although ration packs are designed to meet or exceed the RMDI for all known nutrients, it is known that ADF members habitually discard a significant proportion of their ration pack food. The effects of this on operational fitness are unknown. Australia is the lead nation in an international collaborative study that is being conducted in a hot/wet area (RAAF Scherger, in northern Australia) in April 1999 to determine the effects of long-term feeding with ration packs on physical fitness, clinical/nutritional, physiological, psychological and immunological status of ADF members.

Energy expenditure studies - Navy

Studies of energy expenditure (and hence nutritional requirements) have also been conducted across a range of Naval occupations, with some unexpected results. For example, sailors with apparently relatively sedentary occupations, on board a Fremantle Class patrol boat, had energy expenditure levels that were higher than the mean result for Army recruits and not much lower than that for soldiers training for jungle warfare. At 18 MJ/day, the sailors’ energy requirements were ~50% greater than those of sailors conducting similar activities at a large shore establishment (HMAS Albatross). The most probable explanation for this is that sailors on a small ship must continually shift their centre of gravity to maintain balance on a constantly moving platform as the ship pitches, rolls and yaws. The small muscular contractions required for this evidently lead to a significant increase in daily energy expenditure.

Hydration requirements

Effects of heat on hydration status

As well as nutritional requirements of soldiers and sailors, DNRC contributes to studies of the physiological effects of the environment (especially heat) on military performance. Mention was briefly made above of the soldier modernisation program - Project Wundurra. Of particular interest to CPNB is the thermal stress imposed on soldiers who are engaged in operations in the heat. Last year, a study was conducted to determine the heat strain experienced by soldiers when in the enhanced mode compared to the basic mode (current uniform and equipment).

One of the major protective factors against heat illness is the maintenance of normal body water levels (that is, maintaining euhydration). Hypohydration (a state of lower-than-normal body water) will adversely affect performance when hard work is conducted in the heat. The more severe the hypohydration (which is achieved by the process known as ‘dehydration’) the more severe are the symptoms. This occurs across a continuum, until, at high levels of hypohydration, heat-related illness (including life-threatening heat stroke) becomes inevitable.

DNRC’s contribution in this study was to investigate the effects of heat on hydration status of soldiers in basic mode versus enhanced mode). This required measuring parameters such as water intake, sweat rate, efficiency of sweating and rate of dehydration during short-term patrols in the heat.

98SCSES was conducted in far north Queensland in February 1998. This month was chosen to maximise the heat stress on soldiers. It was conducted at two locations and in two contrasting climatic conditions. High Range Training Area (HRTA), near Townsville, was chosen as a ‘hot/dry’ environment, while Land Command Battle School (LCBS) at Tully was chosen as a ‘hot/wet’ area. Sweat rates were high (1.0-1.5 L/h) in both areas, but sweating efficiency was much lower at LCBS (43%) than at HRTA (82%). Sweating efficiency is a measure of the proportion of sweat that actually evaporates. Any sweat that does not evaporate (drips as liquid from the soldier, or is retained as liquid in his clothing or equipment) represents wasted water: sweating leads to cooling only if the sweat evaporates. The reason for the lower efficiency of sweating at LCBS is that the air was saturated with water vapour (relative humidity was close to 100% for all of the study period). Therefore, soldiers engaged in operations in a hot/wet area such as LCBS will sweat profusely, but most of that sweat will be wasted and body temperatures will rise more quickly than in a hot/dry area, where a higher proportion of sweat evaporates.

Although each patrol conducted at 98SCSES was not long enough for marked hypohydration to be achieved, dehydration did occur, despite the availability of adequate water. It is a common finding that many soldiers (and ground troops in general) do not voluntarily drink enough to maintain a state of euhydration. This phenomenon is known as ‘voluntary dehydration’. In our report we stressed to the ADF that commanders must schedule regular drinking times and check that their troops are drinking at appropriate rates to avoid becoming hypohydrated.

Water carriage and delivery

Also at 98SCSES the opportunity was taken to determine the effects of a new system of water carriage and delivery on soldiers’ hydration status. Currently, the Army relies mainly on water bottles for this purpose. These do not allow soldiers to drink water while moving and do not allow drinking to be hands-free. Commercially available systems now exist, consisting of plastic tanks with tubes, that do allow such drinking. In theory, such water tanks should encourage the soldier to drink more water because he no longer has to stop, lay down his weapon and direct has gaze away from his primary aid - looking for signs of the enemy - in order to drink. A water tank with tube was compared with water bottles in this study to determine the effects on hydration status attributable to water delivery system.

Although a consistent trend to improved hydration status was associated with the use of the tank/tube, the treatment effect did not reach statistical significance for any individual parameter. Similarly, while there was a trend toward less cardiovascular strain (indicative of reduced severity of dehydration), overall, there were no significant differences in thermal strain indices (heart rate, or core or skin temperatures). However, the results of a questionnaire survey showed that in this small sample (ten soldiers) there was universal preference for the tank/tube.

It was concluded that the tank/tube system has operational advantages over water bottles, is more acceptable to soldiers, and does not adversely affect hydration status or thermal strain.

Ergogenic aids

DNRC also has an interest in, and small research program on ‘ergogenic aids’ (EA). EA are substances or techniques that lead to an improvement in one or more component(s) of physical fitness.

The idea that eating particular diets or taking special substances may improve physical fitness is as probably as old as war itself. In 450 BC, Dromeus of Stymphalus (Ancient Greece) recommended that muscle meat be eaten to improve muscular strength. Aztec warriors ate the hearts of particularly brave adversaries in the hope that their courage would be transferred to the victors of the battle. Similarly, for hundreds (if not thousands) of years, athletes have sought a winning edge through the use of reputed EA. In relatively recent times, practices such as water deprivation, leeching, blood letting and the use of enemas have all been tried as potential EA. Of course, these techniques are now known to be extremely unlikely to have any effect other than a detrimental one on physical performance.

More recently, many athletes have tried substances such as desiccated liver, royal jelly, bee pollen, ginseng, B group vitamins, chromium picolinate and a host of other purported EA. The evidence for ergogenic effects is not strong for many of these purported EA. But some substances and techniques are believed to be effective in improving athletic performance; so effective, in fact, that some of them have been banned by the International Olympic Committee because they give an unfair advantage to the user. If these substances/techniques are genuinely effective for athletes, might they also provide a ‘winning edge’ to ADF members engaged in military operations that require physical fitness?

Although a level playing field is essential for athletics, such considerations do not apply in the military context. Any EA that is safe and effective, and gives our troops an advantage over a potential adversary, is worthy of consideration. At this point in the discussion, I should pre-empt any possible misunderstanding about this: no research is being conducted or even considered on harmful or controversial substances such as anabolic steroids. The ADF has a policy that steroids are not to be used by ADF members and research is not planned on these or related substances.

International collaborative and co-operative research on ea

Because there are so many purported EA, Australia could not conduct all the R&D that was necessary with our relatively limited resources. Through membership of a technical panel in The Technical Cooperation Program (TTCP), Australia is involved in international co-operative research into EA (with the UK, US, Canada and New Zealand). The main interest is currently in EA that exert their effects within seven days of application. This is because EA are seen as being of particular value in special operations - activities that must often be conducted with a warning time of only one week or even less. Recently, the panel’s terms of reference were extended to include conventional as well as special operations. Reference to effects of EA on cognitive (mental) performance was also added to the terms of reference.

Compendium of ergogenic aids

The first major output of this panel was a compendium of all substances and techniques whose athletic ergogenic effectiveness is supported by anecdotal or scientific evidence. The compendium (which exists in electronic form for ease of updating) contains about 50 purported EA. For each EA there is a one-page entry, summarising current knowledge of likely ergogenic effects, any potential dangers associated with its use, and whether or not further research needs to be conducted to determine if the EA is likely to be of military value.

From this compendium a list of promising EA was drawn up and a research program (involving international collaborative and co-operative research) was devised. The most promising EA (from the military viewpoint) were considered to include:

Caffeine – this is a stimulant that occurs naturally in tea, coffee and cocoa products. The panel accepts that caffeine has been shown to induce a significant improvement in endurance performance.

Carbohydrate Loading – this is a technique that has been used by marathon runners and triathletes for many years to improve endurance performance.

Creatine – a component of muscle that provides ‘instant energy’ and is believed to reduce recovery time between repeated bouts of anaerobic activity (for example, sprinting).

Blood Loading – a technique that involves taking a quantity (for example, 1 litre) of blood from a soldier, freezing it, and then reinfusing it shortly before the operation; this leads to elevated haemoglobin levels and hence improved aerobic performance.

Rehydration – methods of water delivery or formulations of beverage powder that encourage drinking, increase the rate of water absorption and retention within the body show promise as a means of improving endurance capacity.

Carbohydrate Supplementation – because of the importance of carbohydrate as the preferred fuel for muscular exercise, feeding supplementary carbohydrate to soldiers shows much promise as an effective method for extending the time to fatigue during arduous operations.

While all of the above may have application for the ADF, perhaps the three EA of greatest value in Australia’s (generally) hot climate are rehydration, carbohydrate loading and carbohydrate supplementation. Australia has conducted a study on the effects of carbohydrate loading on military physical performance of Special Operations soldiers and (as described above) has investigated rehydration. Studies are also planned to investigate the most effective carbohydrate/electrolyte beverage powder for use by the military (as opposed to the commercially-available ‘sports drinks’ designed for short-term use by athletes).

Application guidelines

More recently, the panel has developed recommended ‘application guidelines’ for the safe and effective military use of five confirmed EA - blood loading, carbohydrate loading, carbohydrate supplementation, creatine and rehydration. The recommendations are directed to commanders and medical officers. It is stressed in the application guidelines that EA should never be used by individual ADF members without command approval or command knowledge.

These recommended application guidelines have been sent to the Surgeon General of the ADF (SGADF), who is currently devising a policy on EA usage by the ADF. Table 3 shows summaries of two of the five application guidelines that have been sent to SGADF for consideration for application with the ADF. In addition to the completed application guidelines, papers are currently being written on caffeine and heat acclimation as EA of confirmed potential value to the Services.

Among other potential EA that are, or will soon be subject to research, the following two show great promise:

• Modafinil. This chemical was developed to treat a sleep disorder (narcolepsy). It shows considerable potential as an alternative to amphetamines for people engaged in sustained activities that involve sleep deprivation.
• Caffeine + ephedrine. Ephedrine is a naturally occurring stimulant derived from a Chinese plant (of the genus Ephedra). A combination of these two EA seems to have additive (or even synergistic) ergogenic effects on endurance capacity.

Conclusion

In summary, the Defence Nutrition Research Centre of DSTO conducts R&D to determine the nutritional needs of ADF members and ensures that those needs are satisfied by ADF feeding systems. Energy expenditure levels have been shown to vary from 12 MJ to 28 MJ per man per day. ADF ration packs and other feeding systems are being revised to ensure that they satisfy demonstrated nutritional requirements. A study will be conducted to investigate the effects on a wide range of physical and mental parameters (relevant to military performance) of long-term feeding with ration packs. Studies are also being conducted to determine hydration requirements of ADF members and to investigate possible applications of technology to increase water intake and improve hydration status. DNRC is also collaborating with allied nations to determine the potential for improving military physical and cognitive performance through the application of substances and techniques that have been shown to be effective in enhancing athletic performance.

The ultimate aim of all this research is to provide ADF members and those of allied forces with ‘a winning edge’.

Author

Chris Forbes-Ewan has 27 years experience in Defence food science, the last 14 as Senior Nutritionist at DSTO’s Defence Nutrition Research Centre. His main research interest is in the relationship between nutritional and hydration status and military physical performance. Outside Defence nutrition, he has extensive involvement with professional nutrition organisations, particularly education of the general public on the relationships between nutrition, fitness and health.