By Stark, Aliza H Weis, Neta; Chapnik, Leah; Barenboim, Erez; Reifen, Ram
ABSTRACT The purpose of this study was to evaluate the dietary intake of pilots in me Israeli Air Force and to determine whether reported consumption met the Military Dietary Reference Intakes. Thirty-one pilots completed a 24-hour dietary recall and physical activity questionnaire. Blood parameter values were collected from medical records. Results showed that energy-adjusted sample mean intakes of nutrients met the military recommendations with the exceptions of dietary fiber (53% of the recommended level) and calcium (84% of the recommended level). Macronutrient distribution of energy was 17% from protein, 47% from carbohydrate, and 36% from fat. Although saturated fat consumption was not more than 10% of energy, cholesterol consumption was well above the 300 mg/d presently recommended. For all pilots, blood parameter values were in the normal range. Overall, the diet of Israeli pilots was found to be well balanced, but negative dietary patterns (i.e., high cholesterol intake and low fiber intake) characteristic of the general population were observed in this group. INTRODUCTION
Air Force pilots, because of the nature of their work, are selected and monitored to ensure that they are in excellent physical condition. Aircraft flying involves high levels of concentration and attentiveness and quick response times. Outstanding physical performance and mental performance are dependent on many factors, including proper nutrition. To guarantee that personnel receive a well-balanced diet, the U.S. military has established daily nutritional recommendations for healthy, 17- to 50-year-old, physically active, military men. These recommendations, commonly called Military Dietary Reference Intakes (MDRIs), are used as the basis for formulation of garrison and operational meals and rations and can be used for evaluations of the adequacy of food intake.1
It is well known that nutrient deficiencies can adversely affect physical and cognitive performance, as well as immune function and injury recovery.26 In the long term, a healthy diet is associated with lower risks of heart disease, stroke, obesity, and certain cancers.7-11 Therefore, to ensure that Air Force pilots are in the best of health, it is important to evaluate dietary intake and to make recommendations to improve rations if necessary.
Along with assessment of food consumption, numerous parameters can be used to determine overall physical condition and lifestyle patterns. Body weight within recommended limits is assumed to reflect good health.12 Blood parameters can also be used to assess physical condition. Lifestyle is considered to be an important factor in maintaining health. Therefore, nutritional data, physical activity practices, and breakfast consumption were evaluated to provide information regarding lifestyle.
Although several studies have been conducted in combat units, very few studies have assessed the dietary intake of Air Force pilots. The primary objective of this study was to evaluate the dietary intake of pilots in the Israeli Air Force and to determine whether reported consumption met MDRIs.
METHODS
Study Protocol
Interviews and questionnaires were completed either during scheduled annual physical examinations or at the squadron headquarters at various Air Force bases. Pilots were asked to volunteer for the study, and those who agreed to participate filled out a short questionnaire (self-report), followed by a 20-minute interview. The data were collected noninvasively over a 6-month period in 2004, during work hours, by using anonymous questionnaires.
Subjects
Thirty-one Israeli pilots, representing more than five different squadrons, volunteered for this study. The sample included jet fighter pilots, helicopter pilots, and military transport pilots. The study was approved by the internal medical review board of the Israeli Air Force Aeromedicai Center.
Interview
Individual interviews were conducted by a single interviewer with the aid of a questionnaire developed in collaboration witii the Israel Center for Disease Control and the Ministry of Health. The instrument was previously used in the First Israeli National Health and Nutrition Survey and included a validated 24-hour food consumption questionnaire. An atlas of photographs and measuring cups and spoons were used as aids for reporting portion sizes. Additional questions dealt with physical activity and personal preferences regarding foods served in the mess hall on each army base. The use of a single interviewer minimized variability in data collection.
Laboratory and Anthropometric Values
Data such as body weight and height and laboratory blood values were obtained from medical records from recent annual physical examinations. All blood parameters were determined in samples obtained after an overnight fast.
Data Analyses
Data are presented as mean +- SE. Daily nutrient consumption was computed with the aid of Tzemert 1 software (Israeli Ministry of Health), which was designed to calculate >30 nutrients and was developed specifically for use in Israel. The program includes a wide range of local products, with data from manufacturers or data calculated by using the U.S. Department of Agriculture Nutrient Database.13 Sample energy and nutrient means were compared with the MDRIs.1
RESULTS
Anthropometric and Laboratory Data
Table I summarizes descriptive data and biochemical parameters for the 31 male participants in this study. The majority (74%) of pilots had body mass index (BMI) values of
Evaluation of 24-Hour Recall of Food Consumption
The analysis of 24-hour dietary recall data appears in Table II. Self-reported energy intake was lower than calculated energy expenditure for this group of the population. The macronutrient composition of the diet was 17% of energy from protein, 36% of energy from fat, and 48% of energy from carbohydrate. Fatty acid intake was close to recommended values of up to 10% of energy from saturated fatty acids, at least 10% of energy from monounsaturated fatty acids, and ~10% of energy from saturated fats.15 Certain micronutrients were consumed in large quantities and, despite under- reporting, it was clear that these components of the diet were consumed in sufficient quantities (vitamin C, iron, and vitamin B12) or even in excess (cholesterol). To compensate for under-reporting, data were adjusted to energy intake (Table III). Energy-adjusted data showed that calcium and dietary fiber were consumed at levels significantly lower than recommended. Zinc consumption reached only 89% of the recommended value. The majority of the pilots reported that they did not take any dietary supplements; only two reported taking multivitamins, and another two reported taking vitamin C.
Physical Activity
Pilots reported their physical activity and energy expenditure by completing questionnaires regarding specific activities carried out at work and during leisure time. Pilots spent between 5 and 10 h/wk flying, depending on their specific jobs (e.g., helicopter pilot or military transport pilot). Eighty-one percent reported that, aside from actual flying time, the majority of the workday was spent sitting. Two pilots (6%) reported spending most of the workday standing, whereas four pilots (13%) described spending much of the workday walking. During leisure time, 84% of the participants habitually participated in sports, whereas 16% reported no regular physical activity.
Breakfast Frequency
Seventy-four percent of the pilots interviewed regularly ate breakfast in the squadron dining room. However, the energy content of the meal was commonly
DISCUSSION
The purpose of this study was to evaluate the dietary intake of pilots in the Israeli Air Force, to determine whether reported consumption met the MDRIs. It was hypothesized that pilots consumed a healthy diet, but dietary assessment was necessary to confirm or to dispute this assumption. Overall, adjusted sample means indicated that the pilots were consuming an adequate diet, with the exceptions of dietary fiber (53% of MDRI) and calcium (84% of MDRI). Cholesterol consumption was well above recommended levels. Results of blood parameters were in the normal range, and 84% of the participants reported regular physical activity. For the most part, the diet of Israeli pilots was found to be well balanced; however, some dietary habits could be improved. Recommendations include increasing consumption of dietary fiber and calcium, decreasing cholesterol intake, and including breakfast in the daily routine.
Participation in this survey was voluntary, and pilots were self- selected; therefore, a possibility for bias exists. However, the study did reach every branch of pilots in several squadrons and provides meaningful insights concerning the daily eating habits and nutrient consumption in the study population. It should be noted that very few studies have evaluated the nutritional status of Air Force pilots, and this article provides data that are not available elsewhere. As a group, the pilots were found to have optimal body weight, although 26% had BMI values greater than recommended values, with the highest value being 27 kg/m^sup 2^. It must be noted that using the BMI cutoff values for overweight can be problematic when individuals with high muscle mass are being assessed.18-20 A BMI value consistent with overweight does not always indicate that an individual has excess fat mass.
Averages of blood parameters indicated normal values for the Israeli Air Force pilots. In a similar study carried out in the Polish Air Force,21 78% of the 229 fighter pilots participating in the study were reported to have mild, moderate, or severe hyperlipidemia. It should be noted that the mean age for pilots in the Polish study was 36.0 +- 5.2 years, in contrast to the considerably younger pilots in this study. Data for U.S. fighter pilots indicated the average total cholesterol level to be 218 mg/ dL for the 30 men included in the study.22
Reported total energy consumption (2,657 +-168 kcal/d) was significantly lower than both recommended and calculated values for this group. It is well known that underestimation of food intake is pervasive when 24-hour recall methods are used.23,24 Under- reporting by pilots was also found in the work of Copp and Green,22 where an average of 2,585 kcal/d was reported, significantly lower than the recommended range of 2,800 to 3,600 kcal/d. Evaluation of diet adequacy was carried out by using energy-adjusted data, to compensate for under-reporting (Table III).
Macronutrient distribution was 17% of energy from protein, 47% from carbohydrate, and 36% from fat. Almost-identical data were collected in a study of fighter pilots in the U.S. Air Force; mean proportions of energy derived from carbohydrate, protein, and fat were 48.3%, 16.1%, and 34.2%, respectively.22 The MDRI system does not set specific recommendations for macronutrient content of the diet or cholesterol intake but suggests that 10% to 15% of energy be provided by protein, up to 30% of energy be provided by fat, and the remaining 55% to 60% of energy be provided by carbohydrate.1 More- recent standards for the general population have been set by the Institute of Medicine.15 These standards, known as the Dietary Reference Intakes (DRIs), were established in 2004 and set an acceptable range of dietary fat consumption for adults as 20% to 35% of energy intake, with
Evaluation of other dietary nutrients showed that, overall, the diet of fighter pilots provided close to 100% of the recommended values. With the exception of dietary fiber, calcium, zinc, and cholesterol, the consumption of nutrients was between 90% and 200% of the MDRI. According to the First Israeli National Health and Nutrition Survey carried out in 1999-2001,26 the average consumption of dietary fiber for Israeli men 25 to 29 years of age was ~18 g/d, almost identical with the amount reported by the pilots. After adjustment for energy intake, consumption values for dietary fiber were still only 53% of recommended levels.
Calcium consumption for pilots was 84% of recommended levels. This was significantly better than the national average for this age group, which was reported to be 535 mg/d, ~45% of the DRI.15 Dairy products are readily available in the Air Force mess halls and, whereas the national average is one serving of dairy products per day, the pilots consumed closer to two servings per day.
Zinc intake was close to recommended values (89%), and it is unlikely that zinc deficiency would occur at these levels of intake. McClung and Scrimgeour27 reviewed the potential benefits of zinc for soldiers, and from these results it is clear that care must be taken to ensure sufficient intake to prevent zinc status that is less than optimal. Cholesterol consumption was twice the recommended levels. This was largely attributable to high intake levels of both eggs and meat.
Dietary supplement use among the U.S. military has been reported to be high. One study found that 87% of U.S. Army Special Forces soldiers and 76% of support soldiers reported use of multivitamins, sports bars/drinks, and vitamin C.28 In Israel, similar to the United States, dietary supplements are readily available to the public. In marked contrast to the U.S. combat soldiers, Israeli pilots reported relatively low levels of supplement use.
Breakfast habits were variable, although almost all of the pilots ate or drank in the morning hours. Taking into consideration the demands and time constraints on fighter pilots, these data are encouraging. In the study by Copp and Green,22 63% of the pilots reported that they did not eat breakfast daily, and the authors concluded that the irregularity of breakfast consumption was of concern. However, this can easily be compensated for by providing nutritious late-morning snacks to overcome the barriers to consuming an adequate breakfast.
Pilots had 5 to 10 h/wk of flying time. Data on energy expenditure in flight are scarce, and there is insufficient information to accurately account for the amount of additional energy needed for this activity. It is beyond the scope of this study to make an accurate estimation of energy expenditure in this population. It is interesting that a surprising 16% of pilots reported that they did not participate in regular physical activity (>10 min/d).
In conclusion, the general dietary status of the fighter pilots interviewed in this project appeared to be satisfactory. A relatively large number of pilots had BMI values of >25 kg/m^sup 2^. In addition, several reported little or no physical activity beyond what was demanded of them at their jobs. Dietary patterns (i.e., high cholesterol intake and low fiber intake) characteristic of the general population were also observed in this group. This indicates that this population may benefit from a health promotion program that includes both nutrition education, to encourage consumption of a healthy diet, and a regular exercise plan.
ACKNOWLEDGMENTS
We thank Rivkah Goldsmith from the Israeli Ministry of Health for her help and advice concerning questionnaire preparation. In addition, we acknowledge the cooperation and help we received from Sergeant Estevan Malal and other members of the Aeromedicai Center of the Israeli Air Force.
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Aliza H. Stark, PhD*; Neta Weis, BSc*; Leah Chapnik, BSc[dagger]; Erez Barenboim, MD[dagger]; Ram Reifen, MD*
* Faculty of Agricultural, Food, and Environmental Quality Sciences, School of Nutritional Sciences, The Hebrew University of Jerusalem, Rehovot, Israel.
[dagger] Aeromedical Center, Israeli Air Force, Tel HaShomer, Israel.
This manuscript was received for review in September 2007. The revised manuscript was accepted for publication in April 2008.
Reprint & Copyright (c) by Association of Military Surgeons of U.S., 2008.
Copyright Association of Military Surgeons of the United States Aug 2008
(c) 2008 Military Medicine. Provided by ProQuest LLC. All rights Reserved.
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