Submitted by Thomas E. Sather, CAsP (1) , Conrad L. Woolsey (2), Fred Cromartie (3), Marion W. Evans (4)
(1) Naval Aerospace Medical Institute, Pensacola, FL
(2) Logan University, St. Louis, MO
(3) United States Sports Academy, Daphne, AL
(4) University of Western States, Portland, OR
*Corresponding Author – Thomas E. Sather, CAsP
Aviation is an inherently dangerous endeavor. Pilots and aircrew are often directly responsible for aviation mishaps. Moreover, the added stressors such as air combat and fast paced operational tempo further complicate air safety. Due to the intense training and demands of the profession, military aviators are tactical athletes. Military aviation requires special levels of kinesthetic awareness, strength, endurance, eye-hand coordination, and timing. Similar to other highly competitive athletes, aviators often turn to nutritional supplements in attempts to enhance performance. This article reviews the safety and effectiveness of nutritional supplements. Additionally, civilian and military regulations related to the use of supplements in aviation are addressed.
KEYWORDS: Aerospace Physiology, Nutritional Supplements, Energy Beverages
In the world of warfare, being athletic is important from an operational and tactical perspective. Pilots are categorized as athletes due to the fitness and performance standards they must meet on a biannual basis. In the military, the human body is considered as part of the operational weapons system. Whether pulling a trigger or engaging in hand-to-hand combat, the person is an intricate part of the system. Similar to how professional athletes use their bodies to perform in sport and to earn a living, military personnel train their bodies and minds for optimal performance and to survive and even thrive in combat.
Military personnel were once only trained to pass a general physical fitness test twice per year, but are now routinely trained for their job specific duties on a weekly basis. The Navy Operational Fitness and Fueling Series (NOFFS) is one example of new specialized functional training based on a specific skill sets needed. This paradigm shift in thinking marks the emphasis on functional training and the armed forces striving to improve their overall preparedness.
Aviation is inherently dangerous. Pilots are routinely involved in risky situations from take-offs to landings, to flying through thunderstorms. In civilian aviation, there are 16 fatal accidents per every million hours of general aviation, making flying about10 times as dangerous per mile travelled (1). Military pilots fly missions that may involve air-to-air combat (dogfighting), support of ground forces with strategic, low-level bombing or strafing runs, or even searching out enemy missile defenses. In the case of Naval Aviation, aviators must also take off and land on an aircraft carrier at sea, in various environmental conditions.
Military aviators are routinely subjected to environmental stressors as a consequence of mission requirements, airframe, and duty locations. Long duration missions crossing multiple time zones, unusual duty hours, barometric pressure changes, temperature extremes, vibration, noise and G-forces also contribute to increased levels of physical and mental fatigue/stress. Deployed military members often attempt to cope by using energy enhancing supplements to address these actual and perceived reductions in mental and physical performance (2).
Military pilots and aircrew are “tactical” athletes and as such need to be specifically trained to combat the hostile environment they work in. In technical terms, aviators need to be able to perform under environmental conditions that are a combination of high-Gravity force (G-force), low-level (altitude) maneuvers, and conventional 3-dimensional car racing. In NASCAR, drivers experience a maximum of 3 G’s (a measurement of acceleration felt as weight) travelling at over 200 miles per hour; whereas pilots may be subjected to over 12 G’s and travel at speeds faster than the speed of sound. They must also make split-second decisions that mean the difference between life and death. As a result, aircrew must maintain adequate levels of physical fitness. Moreover, the combined effects of a shrinking military force and the expansion of individual operational duties, flight personnel are often over extended with training, deployments, job requirements, and family duties. The cumulative stress of this balancing act can negatively impact performance as well as the safety of missions.
AIRCREW SUPPLEMENT USE
One of the biggest mistakes athletes make is overtraining. Overtraining can lead to injury, staleness, burnout, and ineffective performances. Often the outdated philosophy of ‘more is better’ is incorrectly implemented in training. Rather than taking needed breaks and getting adequate rest, athletes often turn to nutritional supplements with beliefs/hopes that supplements will prevent or minimize the effects of not getting adequate rest.
It appears that the use of nutritional supplements by military members follows trends from the general population. In the United States, research suggests that over half of the adult population (aged 20 years or older) uses or has used supplements (3). Self-reported surveys on various military groups indicate that between 60-85% use or have used supplements (4). Moreover, in surveys administered to deployed personnel, 47% reported using at least one type of supplement and 22% reported using multiple supplements (2). Additionally, research indicates greater use of energy enhancing supplements among deployed military members. This finding is not surprising given that it is relatively common for combat troops to be sleep deprived and given the operational tempo they are expected to maintain. This is especially concerning as military members often work in extreme environments and supplements can interfere with normal physical and mental performance.
In the aviation environment, commonly used supplements can have unforeseen effects. These effects, which would not be an issue for personnel working on the ground, could potentially have catastrophic consequences. For example, as a result of supplement use, a Navy pilot has temporarily blacked out before during ‘final approach’. In this incident, the pilot had recently started a vitamin regimen which contained vitamin B-3 (niacin) and Coenzyme Q10 (a commonly used antioxidant). It was later discovered that the combination of niacin and Coenzyme Q10 can cause a drop in the blood pressure and peripheral vascular resistance, which resulted in reduced G-force tolerance. This unexpected drop in G-tolerance may well have caused a crash had the pilot not aborted landing at the last minute (5).
Military Regulations on Supplement Use
A cursory review of regulations on the use of nutritional supplements has revealed a fragmented approach. The Federal Aviation Administration (FAA) places no limitations on the use of supplements as they are not treated as medications to be regulated (6).
Within the Department of Defense (DOD), regulations on the use of over-the-counter (OTC) supplements vary from service to service. The United States (US) Coast Guard ascribes to limitations set by the Food and Drug Administration (FDA) and National Collegiate Athletic Association (NCAA). In the US Air Force, the decision on which supplements are allowable is left to the discretion of the flight surgeon (7).
The US Army and Navy both place more limits on the use of supplements on pilots and aircrew. The US Army requires that all pilots report any supplement use to their flight surgeon. The Army also classifies nutritional supplements as falling within one of three categories (i.e., Class 1, 2, or 3) with specific limitations for use associated with each. Class 1 supplements can be used without approval of a flight surgeon. These supplements include single daily multivitamin/minerals, vitamin C, E, B6, B12 (oral), calcium, folate, protein supplementation, including shakes, capsules, and nutritional bars. Pilots must declare the use of all Class 1 supplements in writing on the Flying Duty Medical Examination (FDME) / Flying Duty Health Screen (FDHS). Class 2 supplements include vitamins A, K, D, niacin, riboflavin, thiamine, magnesium, zinc, chromium, selenium, copper, glucosamine with or without chrondroitin, echinacea, saw palmetto, creatine, and ginseng. These substances can be used only with approval of a flight surgeon and must be declared on the FDME/FDHS. Class 3 supplements are any other supplements that are not previously listed and are not authorized for use.
The US Navy provides the most extensive guidelines for nutritional supplement use. However, the Department of the Navy does not have a specific policy on the use of supplements. Navy and Marine Corps aviation is controlled by the Chief of Naval Operations and Instructions 3710.7U which states, “Use of nutritional/dietary and other OTC supplements/products by flight personnel except those approved by BUMED is prohibited. Flight Surgeons shall be consulted to assist with making informed decisions regarding nutritional supplements. The use of nutritional supplements of all types shall be reported to the flight surgeons and recorded during every periodic physical examination or physical health assessment (PHA).” Therefore, flight surgeons defer to the Aeromedical Reference and Waiver Guide (ARWG) to determine which supplements are authorized for use by pilots and aircrew (8). The US Navy ARWG is published by the Naval Aerospace Medical Institute and classifies nutritional supplements as belonging to one of three categories similar to that of the Army. Class A supplements are authorized for use by aviation personnel without restriction as long as they are disclosed during the physical. These include sports drinks, multivitamins, protein supplements, and tonic water. Class B supplements are more restrictive and require a positive diagnosis of a medical condition prior to clearance for use. The supplements in this category are glucosamine with or without chondroitin for arthritis, and saw palmetto for benign prostate hyperplasia. Anything else that is not explicitly permitted is classified as a Class C supplement and is not authorized for use. Personnel taking these substances should be removed from aviation duty for a minimum of 24 hours after the last dose of the substance.
In reviewing the supplements authorized for use by flight crews, there are three general groups of supplements that are commonly used by aviators. The first are general nutritional supplements that include traditional multi-vitamins, minerals, and essential nutrients. The second list includes nutritional derivatives of protein and carbohydrates. The third are herbs or other “natural” compounds that are advertised to impart some type of physiological enhancement such as more energy, speed in healing, or boost in immune functions.
From a safety perspective, there appears to be no limit as to the quantity or quality of vitamins and mineral supplementation. While generally regarded as safe (GRAS), this overly permissive policy is one area of concern. The unregulated use of vitamins and minerals may lead to occurrences of hypervitaminosis as individuals consume supplements with high quantities of vitamins in the hopes of either enhancing endurance or improving energy levels. One nutritional supplement that contains massive doses of vitamins is energy shots. Some energy shots have in excess of 8000% of the RDA for certain B vitamins per two ounce bottle.
Protein and carbohydrate supplementation has been studied by sports researchers for decades. Both macronutrients have been proven safe and useful in optimizing physical performance in athletes. Since aviators typically use both protein and carbohydrate supplements, it is warranted that these products be adequately evaluated for safety.
Proteins are made up of individual amino acids and are used to make up most biologically active tissues. There are nine amino acids that that body cannot produce and therefore must be consumed daily. The body can combine different amino acids with carbohydrates, fats, and ammonia in different configurations to create what it needs. Some animal and human studies even present several plausible mechanisms through which specific amino acids may decrease the risk of diseases such as coronary heart disease (9). Literature reviews indicate that protein intake at the levels set by the FDA seem insufficient for athletes to maintain a positive nitrogen balance. This balance is important as it serves as an indirect measure of whether the body is repairing and building muscle (anabolism) or tearing it down (catabolism). For an athlete, it is imperative that they maintain a positive nitrogen balance as this ensures the body is adequately repairing itself and building verses breaking down its natural resources for energy.
Protein, when taken in large quantities, could be detrimental to the human body. Theoretically, ingestion of large amounts of protein stresses the liver and kidneys and could lead to pathological changes in kidney function as a result of the deamination of proteins and disposal of the extra nitrogenous waste (10). It has been suggested that excessive protein intake leads to a progressive impairment of kidney functions (11). These findings are applicable when dealing with a patient population with kidney disease or dysfunction; however, evidence does not support these findings in healthy populations (12). While experts have not determined the upper limits of safe protein intake, caution is warranted when exceeding the 2.0 gram per kilogram per day intake level (13).
Phosphocreatine is a naturally occurring compound that could potentially enhance training by increasing energy storage. Creatine has the ability to increase energy transport by acting as a phosphate donor. By donating a phosphate to the active muscle, adenosine diphosphate can be synthesized into adenosine triphosphate (ATP). ATP is used for muscle contractions. The extra reserve of energy can allow for a longer and harder training session as long as the athlete stays fully hydrated. These ergogenic effects in turn can allow for improvements in strength and body mass (14). Creatine may not be beneficial for every type of training. While strength athletes have made good gains by using creatine, the same cannot be said for endurance athletes such as marathon runners or cyclists (15).
Sports drinks consist of water, carbohydrates, and electrolytes and are relatively safe to use. They have been shown to help performance during continuous activity lasting longer than 90 minutes because they are absorbed faster than water. They also contain electrolytes, which stimulate thirst and help retain water (16).
To ensure that the muscles have enough fuel to perform a task, carbohydrate replacement products can be consumed at periodic intervals. Research suggests that in endurance type sports, the optimal blend of carbohydrates is a mixture of the different types of sugars (17). Once those fuels are used up, it is imperative to refuel. Carbohydrates are the easiest for the body to use and digest. Research has shown that the optimal window to resupply muscles with carbohydrates is soon after exercise. This helps with restoring our glycogen stores. Additionally, the recovery process and metabolic absorption of protein is improved with carbohydrate intake directly after exercise (18). This is an especially important for athletes that are on a low carbohydrate or calorie restricted diet.
One of the most contested categories of nutritional supplements used by aviators is herbs and natural compounds. The premise behind this category of supplements is that these substances will impart some sort of physiological enhancement. Most herbal supplements that can stimulate the body are not authorized for use by aviators. Herbal stimulants such as ephedrine and 1,3-dimethylamylamine (AKA: DMAA, methylhexanamine, or geranium extract) have been removed from the market due to numerous health issues associated with the use of these products. One exception to the prohibition of herbal stimulants is caffeine.
Caffeine is classified as a methylxanthine and stimulates the nervous and cardiac systems while at the same time relaxing smooth muscle cells. Xanthene use is not unusual in civilized society and is one of the most commonly used drugs on a daily basis (19). These chemicals are routinely consumed by the general population and are relatively safe if used in moderation. In some populations, xanthenes may contribute to anxiety (20). Methylxanthines are also used by asthma and pulmonary patients as a bronchodilator (21). Caffeine has been researched substantially and has been shown to be a potent ergogenic that can enhance endurance with restricted use. Recent research even suggests that caffeine has antioxidant effects and may help protect people from diseases such as Alzheimer’s when consumed in moderate amounts (22). While caffeine is generally regarded as safe, mixing with other ingredients or consuming rapidly can be dangerous.
Energy drinks have become popular and contain large amounts of vitamins, amino acids, and caffeine. While not authorized for use by flight personnel, their presence in convenience stores and military commissaries is concerning. With the introduction of these products, caffeine poisoning or overdose has become more common in the civilian sector (23). Caffeine toxicity can mimic amphetamine poisoning and lead to seizures, psychosis, cardiac arrhythmias and potentially death. According to research conducted in Australia, a majority of the emergency calls involving energy drinks were received between 5pm and 3am with the consumer drinking an average of five energy drinks (24). Ironically, this happens to be the time when party-goers and study-crammers likely seek the advertised ‘energy boost’ of these drinks.
SUMMARY & CONCLUSION
Research shows that supplement use by aviation personnel follows the same usage patterns seen in the general population. In combat deployed troops, there are a number of findings regarding the use of nutritional supplements that make logical sense. The finding that more deployed military members used energy enhancing supplements is not surprising given the operational tempo typical of combat duty. It is relatively common amongst combat troops to be sleep deprived. Additionally, the use of protein supplementation by deployed personnel was also not alarming given that combat personnel must maintain strength for carrying equipment, body armor and personnel supplies.
In the realm of military aviation, it is not surprising that there variations in standards related to the use of supplements. Divided into four service branches, each has different policies governing the use of supplements. As supplements are not well regulated by the federal government as is drugs, it falls to each service branch to establish policies. Additionally, since supplement products often rapidly change, it is almost impossible for any federal agency to survey new products and determine efficacy. The branch medical chiefs seem more comfortable in deferring to policies of outside agencies such as the NCAA or even the United States Olympic Committee in order to survey product safety. While this is a good start, it does not explore the special aeromedical concerns such as effects at altitude, G-forces, and other aspects of military readiness in aviation personnel. It will take continued effort by military medical officers to tackle this issue given the continuous advancements in sports nutrition and the billion dollar marketing efforts of the supplement industry.
Since nutritional supplements cannot be regulated as drugs, efforts must be focused to educate pilots and aircrew while continuing to research the physiological effects of supplements. It is important to realize that there will never be a way to regulate human behavior, dietary habits, and the use of nutritional supplements without major changes in governmental legislation. However, through health education and regulations, we can influence the behavior of service personnel thereby potentially reducing the adverse risks of supplementation while optimizing health and wellbeing.
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