Dietary Support of Extended-Duration Bed Rest Studies AM Inniss1, BL Rice2, SM Smith3 1General Clinical Research Center University of Texas Medical Branch at Galveston Galveston, TX 77555 2Enterprise Advisory Services, Inc. Houston, TX 77058 3Human Adaptation and Countermeasures Office NASA Lyndon B. Johnson Space Center Houston, TX 77058 Running head: Dietary Support Word count for abstract: 188 Word count for narrative text: 3798 Number of references: 5 Number of tables: 1 Number of figures: 1 Sources of support: This project was supported by the National Aeronautics and Space Administration Flight Analogs / Bed Rest Research Project. Keywords: nutrition; food support; menu planning; bed rest ABSTRACT Dietary control and nutrient intake are critical aspects of any metabolic study, but this is especially true in the case of bed rest studies. We sought to define nutrient requirements, develop menus, and implement them in a series of three long-duration bed rest studies. With regard to energy intake, the goal was to maintain subject body weight to within 3% of their body weight on day 3 of bed rest (after fluid shift had occurred). For other nutrients, intakes were based on the NASA space flight nutritional requirements (with some adaptations based on the ground-based model used here). A secondary goal was to develop menus with foods similar to those expected to be approved for space flight (however, this was relaxed to attain desired nutrient intakes). This paper also describes the role of the research dietitian as part of the multi-disciplinary team and the importance of the metabolic kitchen staff. It also provides insight into some of the dietary challenges that arise during extended-duration bed rest studies. Regardless of the overall objective of the study, nutrition must be carefully planned, implemented, and monitored for results to be uncompromised. INTRODUCTION Bed rest is an analog for simulating the effects of weightlessness on physiological systems (5). Nutrition and dietary support are critical for bed rest studies, and problems or issues can greatly affect even the best-designed study. Subject selection and retention may be adversely affected by the type and quantity of food. The fact that energy expenditure decreases during bed rest, and thus maintenance of body mass requires reduction of food intake, must be taken into account when controlling intake of specific nutrients. Although this is usually easy to accommodate, it can affect a researcher’s ability to achieve constant total intake and a constant percent of the diet for the nutrient. Preventing subject boredom with menu cycles can also prove to be a difficult task. ROLE OF THE RESEARCH DIETITIAN AND SUPPORT STAFF The research dietitian is a valuable member of the research team and contributes to the success of the study. Before the study starts, the dietitian works with the investigator team(s) to ensure that all dietary restrictions are met, develops the menus to meet the nutrient requirements, purchases and manages food items for the metabolic kitchen, and works with the subject- screening team to address and resolve any dietary issues, such as subject food allergies or intolerances. Once the study starts, the dietitian interacts daily with the research subjects to discuss dietary issues, monitors subjects’ weight, and ensures that subjects maintain maximum dietary compliance. This continuous interaction fosters a sense of rapport with the subjects and may be psychologically beneficial to them, and thus promote their continued participation in the study. The dietitian also works closely with the nursing staff to communicate in a timely fashion any issues that may involve the medical care of the subjects. The research dietitian is also responsible for overseeing the metabolic kitchen staff in the preparation of the meals, tracking caloric and nutrient intake for each subject via the nutrition database, and performing analysis of nutrient intake data. The metabolic kitchen staff is responsible for preparing the meals, encouraging 100% compliance with the consumption of all meals, and ensuring that the subjects eat according to schedule. METHODS Eleven healthy subjects (8 men, 3 women) participated in the project, which was conducted in three studies (designated Study 1, 2, and 3). The subjects’ mean age (± SD) was 34.8 ± 9.3 y. Average height of the study group was 169 ± 10 cm, and average weight was 73.6 ± 15.5 kg. Subjects had to successfully pass various physical and psychiatric examinations to be included in the study. As required by the NASA Bed Rest Standardization Protocol, subjects were excluded from the study if they did not meet the minimum testing requirements recently had sub-standard nutritional status, had gastro-esophageal reflux disease, had a history of diabetes, or took medication that would interfere with the interpretation of results. All subjects were given written and verbal explanation of testing and bed rest protocols, and signed documentation indicating their understanding and consent. All protocols were reviewed and approved by the National Aeronautics and Space Administration (NASA) Johnson Space Center and the University of Texas Medical Branch at Galveston (UTMB) Institutional Review Boards. Bed rest was conducted under medically supervised conditions at the General Clinical Research Center at UTMB in Galveston, TX. The ambulatory phase allowed subjects to become acclimated to the research environment and to the research diet. During the bed rest phase of the study, subjects were placed at a 6° head- down tilt. They were allowed to either elevate themselves on one elbow or turn over on their stomachs to consume meals; otherwise they were restricted to the head-down position. Nutrient Requirements The study diet was designed to approximate the diet consumed by space shuttle astronauts and consisted of standard foods. At baseline, its composition was 55% carbohydrates, 30% fat, and 15% protein. Dietary constraints included no caffeine, cocoa, chocolate, tea, or herbal beverages. Caloric requirements were individualized for each subject. The Harris-Benedict Equation (1) for calculation of resting energy expenditure was used to estimate caloric intake: Men: (kcal/d) = 66.47 + (13.75 x weight (kg)) + (5.00 x height (cm)) – (6.76 x age) Women: (kcal/d) = 655.10 + (9.56 x weight (kg)) + (1.85 x height (cm)) – (4.68 x age) Activity factors of 1.6 and 1.3 were used for ambulatory and bed rest phases, respectively. These were based on data from previous bed rest studies. The primary goal of dietary support was for subjects to maintain pre-bed rest body weight. To this end, caloric intake was adjusted as necessary to maintain body weight, which was recorded daily using a bed scale. Subjects were weighed each morning before they had breakfast. Dietary intervention to prevent weight loss occurred if a subject’s body weight deviated by 3 or more percent from their weight on bed rest day 3, when the initial fluid shift and any diuresis resulting from postural change should have been completed. Caloric intake was manipulated by increasing carbohydrates and fat while keeping protein constant. The target intake of nutrients (Table I) was based on the NASA space flight nutritional requirements, with some adaptations based on the ground-based model used here to make a set of Flight Analogs / Bed Rest Research Project nutrient intake requirements (NASA bed rest requirements). Calcium and phosphorus intake were targeted to be about 1400 mg/d. Sodium was targeted to be 2 mmol/kg(cid:215)d–1 and potassium, 1.2 mmol/kg(cid:215)d–1. Target fluid intake was 28.5 ml/kg body weight. Filtered water was provided for drinking and used in food preparation. For other nutrients, average intake was considered acceptable if it met 100-125% of NASA bed rest requirements, with daily intake not less than 80% of the requirement. All diets were composed, and actual dietary intakes were determined, using the Nutrition Data System for Research (NDS-R) software, version 5.0_35, May, 2003, developed by the Nutrition Coordinating Center, University of Minnesota, Minneapolis, MN (4). Menu Development A secondary goal of dietary support was to develop menus with foods similar to those expected to be approved for space flight. However, constraints on food for space flight sometimes conflicted with another secondary goal of providing subjects with a product that was acceptable in variety, flavor, visual and aromatic appeal, texture, form, and shape, while at the same time achieving an acceptable nutrient value range. The amount of fresh foods is quite limited on a long-duration mission. Meat, fish, and poultry were provided to the bed rest subjects and prepared in various ways throughout the menu cycle, and a variety of fruits and vegetables were used. There was a shift from using frozen fruits in Studies 1 and 2 to using fresh fruits in Study 3. A greater variety of fresh fruit was also added to the menu for Study 3. This single change greatly improved the overall taste and visual appeal of the breakfast menus. The availability of fresh fruit throughout the year was an important consideration when designing the menu. The vegetables used during the studies were usually frozen because of the stability of frozen vegetables and their availability at any time of year. Nutrient content was another important factor in the selection of food items and recipes. Certain drinks were chosen that were fortified with vitamins A, C, and E. Other juices, such as orange juice, were chosen because they were fortified with calcium and vitamin D. Other food items were selected because they were fortified with folic acid and vitamin D. Several ready-to- eat and heat-and-serve food items were incorporated into the menus. These quick and easy food items provided balance on days when extensive food preparation was required for other items. Several recipes for mixed dishes were chosen, as they incorporated more foods, such as fish and dairy products, that are high in calcium and vitamin D. The sodium content of the food items was another important factor in composing menus and developing recipes. Many of the pre-packaged food items include some form of sodium as a preservative. Care was therefore taken to limit the amount of salt added to menu items. In addition, minor changes were made to reduce the amount of sodium added throughout the studies. In Studies 1 and 2, regular salt was used. In an attempt to achieve an acceptable sodium intake range for Study 3, low-sodium salt was used in all recipes. Similarly, unsalted butter was used instead of salted butter. The subject population was also a major consideration in the planning of the menus. The menus were devised to reflect the diversity of cultures and ethnicities in the subject population. Subjects had a variety of taste preferences and food aversions, and care was taken to create a menu cycle that would represent this diversity and accommodate all subjects. The meals were designed to provide as much color and contrast as possible to make each dish look attractive to the subjects. The menus included desserts such as cookies, pies, and ice cream. Careful menu planning ensured that a particular food item was not served more than once in the same day. The menus were placed in order by meal and by day. This allowed the dietitian to see the layout of the menu cycle and to ensure that the same types of foods were not served at the same meal on consecutive days. After the menu cycle was set, the nutrient analysis was done to ensure that the nutrient requirements were met. A 7-d menu cycle was implemented for the 60-d Study 1. For Studies 2 and 3 (90-d studies), a 10-d menu cycle was provided to coincide with the greater number of bed rest days and ensure that subjects did not receive the same meal on the same day of each week. The menus were altered to accommodate certain study protocols. Tests that influenced the menus included the oral glucose tolerance test, the glucose breath test, and the cardiovascular test. Subjects were to avoid any gas-producing foods the night before they took the glucose breath test. To ensure that the overall carbohydrate intake remained stable, 50 g of carbohydrate was eliminated from the diet on the days that the dextrose was given. Similarly, the oral glucose tolerance test required 75 g of glucose to be removed from the diet. Because both tests rarely fell on the same menu cycle day, two additional variations of the original 10-d menu cycle were created that reflected the changes in carbohydrate. This resulted in a total of three 10-d menu cycles per subject. The cardiovascular test required subjects to consume a light meal of predominantly complex carbohydrates before they participated in the test. Subject Screening Process Subject candidates were provided with sample menus before they met with the dietitian. They were instructed to identify foods to which they had allergies and foods that they absolutely could not tolerate throughout the study, by placing a check mark next to those foods on the menus. Once the preference forms were completed, the information was forwarded to the dietitian and reviewed. On the day of subject screening at the Flight Analogs Research Center at UTMB, the dietitian visited each subject candidate to discuss food preferences and to get a better understanding of why certain foods were eliminated. During this time, it was discussed at length that the menus were standardized, but minor allowances would be made to accommodate subjects with adverse reactions to certain foods. Subjects were informed that all meals would be prepared in the metabolic kitchen, that they were expected to eat 100% of all meals, that no other food items were allowed in the rooms, and that visitors were not allowed to enter subjects’ rooms with food. Any questions or concerns that the subject candidate had at this time were addressed. The dietary preference forms were then signed by the subject and the dietitian upon agreement that the subject understood the dietary expectations. This dietary screening process was also discussed in an orientation session entitled “A Day in the Life”. This session introduced prospective subjects to the unit and allowed them to meet the nursing and dietary staff and ask questions about their stay on the unit. This orientation session was included in the consent process and was conducted by the nursing staff. Kitchen Activity and Meal Serving Schedules Menus prepared using NDS-R were converted into menu sheets using Microsoft(cid:212) Excel. The sheets were updated daily to reflect dietary changes and then were forwarded to the dietary staff. The updated sheets were placed in the appropriate subject’s binder. Each menu sheet was labeled with the subject’s name , date, bed rest day, the meals that were being prepared for the day, and the gram amount of each food item. Any discrepancies in the amount of foods consumed by each subject were recorded at the end of each meal. All foods were weighed to – 0.1 g using Mettler Toledo scales. All subjects received the same meal each day, except for minor variations that reflected each subject’s food preferences, or study protocol constraints as described earlier. Food portion sizes were different for different subjects because of different estimated caloric intake requirements. To ensure that each subject received the correct amount of each food item, each tray was labeled with the subject’s name and dated. The date on the tray was the day that the meal was to be consumed. Food items were prepared one day in advance, and a portion was weighed out for each subject and placed in a separate container until the time for meal preparation. In order for