Reducing Stress Fracture in Physically Active Military Women

Subcommittee on Body Composition, Nutrition, and Health of Military Women

Committee on Military Nutrition Research

Food and Nutrition Board

INSTITUTE OF MEDICINE

NATIONAL ACADEMY PRESS
Washington, D.C. 1998



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Reducing Stress Fracture in Physically Active Military Women Subcommittee on Body Composition, Nutrition, and Health of Military Women Committee on Military Nutrition Research Food and Nutrition Board INSTITUTE OF MEDICINE NATIONAL ACADEMY PRESS Washington, D.C. 1998

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NATIONAL ACADEMY PRESS 2101 Constitution Avenue, N.W. Washington, DC 20418 NOTICE: The project that is the subject of this report was approved by the Governing Board of the National Research Council, whose members are drawn from the councils of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The members of the committee responsible for the report were chosen for their special competences and with regard for appropriate balance. The Institute of Medicine was established in 1970 by the National Academy of Sciences to enlist distinguished members of the appropriate professions in the examination of policy matters pertaining to the health of the public. In this, the Institute acts under both the Academy's 1863 congressional charter responsibility to be an adviser to the federal government and its own initiative in identifying issues of medical care, research, and education. Dr. Kenneth I. Shine is president of the Institute of Medicine. Support for this project was provided by the U.S. Army Medical Research and Materiel Command through contract no. DAMD17-95-1-5037. The views presented in this publication are those of the Subcommittee on Body Composition, Nutrition, and Health of Military Women and are not necessarily those of the sponsor. Library of Congress Catalog Card No. 98-87880 International Standard Book Number 0-309-06091-5 Additional copies of this report are available from: National Academy Press 2101 Constitution Avenue, N.W. Lock Box 285 Washington, DC 20055 Call (800) 624-6242 or (202) 334-3313 (in the Washington metropolitan area), or visit the NAP's on-line bookstore at http://www.nap.edu. For more information about the Institute of Medicine and the Food and Nutrition Board, visit the IOM and FNB home pages at http://www2.nas.edu/iom/ and http://www2.nas.edu/fnb/. Copyright 1998 by the National Academy of Sciences. All rights reserved. Printed in the United States of America The serpent has been a symbol of long life, healing, and knowledge among almost all cultures and religions since the beginning of recorded history. The image adopted as a logotype by the Institute of Medicine is based on a relief carving from ancient Greece, now held by the Staatliche Museen in Berlin.

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SUBCOMMITTEE ON BODY COMPOSITION, NUTRITION, AND HEALTH OF MILITARY WOMEN BARBARA O. SCHNEEMAN (Chair), College of Agricultural and Environmental Sciences, University of California, Davis ROBERT O. NESHEIM (Vice Chair), Salinas, California JOHN P. BILEZIKIAN, Department of Medicine, College of Physicians and Surgeons, Columbia University, New York, New York NANCY F. BUTTE, Children's Nutrition Research Center, Baylor College of Medicine, Houston, Texas STEVEN B. HEYMSFIELD, Human Body Composition Laboratory, Weight Control Unit, and Obesity Research Center, St. Luke's-Roosevelt Hospital Center, New York, New York ANNE LOOKER, Division of Health Examination Statistics, National Center for Health Statistics, Hyattsville, Maryland GORDON O. MATHESON, Division of Sports Medicine, Department of Functional Restoration, Stanford University School of Medicine, Stanford, California BONNY L. SPECKER, The Martin Program in Human Nutrition, South Dakota State University, Brookings Committee on Military Nutrition Research Liaison GAIL E. BUTTERFIELD, Nutrition Studies, Palo Alto Veterans Affairs Health Care System and Program in Human Biology, Stanford University, Palo Alto, California Food and Nutrition Board Liaison JANET C. KING, U.S. Department of Agriculture Western Human Nutrition Research Center, San Francisco and University of California, Berkeley Military Liaison Panel CAROL J. BAKER-FULCO, Military Nutrition and Biochemistry Division, U.S. Army Research Institute of Environmental Medicine, Natick, Massachusetts LT LESLIE COX, USN, Bureau of Naval Personnel, Washington, D.C. LTC BETH FOLEY, USA, Health Promotion Policy, Department of the Army, Washington, D.C. JAMES A. HODGDON, Human Performance Department, Naval Health Research Center, San Diego, California COL ESTHER MYERS, USAF, Biomedical Science Corps for Dietetics, 89 Medical Group, Andrews AFB, Maryland CDR JANEE PRZYBYL, USN, National Naval Medical Center, Bethesda, Maryland MAJ JOANNE M. SPAHN, USAF, Nutritional Medicine Service, 3rd Medical Group/SGSD, Elmendorf AFB, Alaska MAJ VICKY THOMAS, USA, Office of the Surgeon General, Department of the Army, Falls Church, Virginia CDR FAYTHE M. WEBER, USN, Medical Service Corps, Bureau Medicine and Surgery, Washington, D.C. U.S. Army Grant Representative LTC KARL E. FRIEDL, USA, Army Operational Medicine Research Program, U.S. Army Medical Research and Materiel Command, Fort Detrick, Frederick, Maryland

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Staff REBECCA B. COSTELLO (through May 22, 1998), Project Director MARY I. POOS (from May 23, 1998), Project Director SYDNE J. CARLSON-NEWBERRY, Program Officer SUSAN M. KNASIAK-RALEY (through April 3, 1998), Research Assistant MELISSA L. VAN DOREN, Project Assistant

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COMMITTEE ON MILITARY NUTRITION RESEARCH ROBERT O. NESHEIM (Chair), Salinas, California WILLIAM R. BEISEL, Department of Molecular Microbiology and Immunology, The Johns Hopkins University School of Hygiene and Public Health, Baltimore, Maryland GAIL E. BUTTERFIELD, Nutrition Studies, Palo Alto Veterans Affairs Health Care System and Program in Human Biology, Stanford University, Palo Alto, California WANDA L. CHENOWETH, Department of Food Science and Human Nutrition, Michigan State University, East Lansing JOHN D. FERNSTROM, Department of Psychiatry, Pharmacology, and Neuroscience, University of Pittsburgh School of Medicine, Pennsylvania ROBIN B. KANAREK, Department of Psychology, Tufts University, Boston, Massachusetts ORVILLE A. LEVANDER, Nutrient Requirements and Functions Laboratory, U.S. Department of Agriculture Beltsville Human Nutrition Research Center, Beltsville, Maryland JOHN E. VANDERVEEN, Office of Plant and Dairy Foods and Beverages, Food and Drug Administration, Washington, D.C. DOUGLAS W. WILMORE, Department of Surgery, Brigham and Women's Hospital, Boston, Massachusetts Food and Nutrition Board Liaison JOHANNA T. DWYER, Frances Stern Nutrition Center, New England Medical Center Hospital and Departments of Medicine and Community Health, Tufts Medical School and School of Nutrition Science and Policy, Boston, Massachusetts U.S. Army Grant Representative LTC KARL E. FRIEDL, USA, Army Operational Medicine Research Program, U.S. Army Medical Research and Materiel Command, Fort Detrick, Frederick, Maryland Staff REBECCA B. COSTELLO (through May 22, 1998), Project Director MARY I. POOS (from May 23, 1998), Project Director SYDNE J. CARLSON-NEWBERRY, Program Officer SUSAN M. KNASIAK-RALEY (through April 3, 1998), Research Assistant MELISSA L. VAN DOREN, Project Assistant

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FOOD AND NUTRITION BOARD CUTBERTO GARZA (Chair), Division of Nutrition, Cornell University, Ithaca, New York JOHN W. ERDMAN, JR. (Vice Chair), Division of Nutritional Sciences, College of Agriculture, University of Illinois at Urbana-Champaign LINDSAY H. ALLEN, Department of Nutrition, University of California, Davis BENJAMIN CABALLERO, Center for Human Nutrition, The Johns Hopkins School of Hygiene and Public Health, Baltimore, Maryland FERGUS M. CLYDESDALE, Department of Food Science, University of Massachusetts, Amherst ROBERT J. COUSINS, Center for Nutritional Sciences, University of Florida, Gainesville JOHANNA T. DWYER, Frances Stern Nutrition Center, New England Medical Center Hospital and Departments of Medicine and Community Health, Tufts Medical School and School of Nutrition Science and Policy, Boston, Massachusetts SCOTT M. GRUNDY,* Center for Human Nutrition, University of Texas Southwestern Medical Center at Dallas CHARLES H. HENNEKENS, Harvard Medical School and Brigham and Women's Hospital, Boston, Massachusetts SANFORD A. MILLER, Graduate School of Biomedical Sciences, University of Texas Health Science Center, San Antonio ROSS L. PRENTICE,* Division of Public Health Sciences, Fred Hutchinson Cancer Research Center, Seattle, Washington A. CATHARINE ROSS, Department of Veterinary Science, Pennsylvania State University, University Park ROBERT E. SMITH, R. E. Smith Consulting, Inc., Newport, Vermont VIRGINIA A. STALLINGS, Division of Gastroenterology and Nutrition, The Children's Hospital of Philadelphia, Pennsylvania VERNON R. YOUNG,*, † Laboratory of Human Nutrition, School of Science, Massachusetts Institute of Technology, Cambridge Ex-Officio Member STEVE L. TAYLOR, Department of Food Science and Technology and Food Processing Center, University of Nebraska, Lincoln Staff ALLISON A. YATES, Director GAIL SPEARS, Administrative Assistant *   Member, Institute of Medicine. †   Member, National Academy of Sciences.

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Preface HISTORY OF THE SUBCOMMITTEE The Subcommittee on Body Composition, Nutrition, and Health of Military Women (BCNH subcommittee) was established in 1995 through a grant administered by the U.S. Army Medical Research and Materiel Command as part of the Defense Women's Health Research Program. Under the guidance of the Committee on Military Nutrition Research (CMNR), the BCNH subcommittee was asked to evaluate whether existing body composition and physical appearance standards for women in the military conflicted with body composition requirements for task performance and if these same standards might interfere with readiness by encouraging chronic dieting, inadequate intake, and sporadic fitness. The BCNH subcommittee conducted an extensive review of this topic, including a workshop held in September 1996 to gather information on current knowledge and activities relating to achieving fitness and readiness for military women. Additionally, the subcommittee sought to identify factors that would interfere with the readiness and long-term health of military women. A report of this activity has been completed recently (IOM, 1998).

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COMMITTEE TASKS AND PROCEDURES One of the tasks specifically delineated for the BCNH subcommittee was to identify and provide recommendations regarding special nutritional considerations of active-duty military women. An area identified for further study in military women concerns the effect of calcium status, as well as total energy intake, on the incidence of stress fractures in the short term, and osteoporosis in the long term, and the nutrient implications of these conditions. The incidence of stress fractures during basic training is substantially higher in female than in male recruits (IOM, 1992, 1998). This injury has a marked impact on the health of service personnel and imposes a significant financial burden by delaying the training of new recruits. Stress fractures increase the length of training time, program costs, and time to military readiness. In addition, stress fractures and short-term risks to bone health may share their etiology with the long-term risk of osteoporosis. The incidence of stress fracture in male military recruits has been reported to range from 0.2 percent in U.S. Navy recruits to 4.5 percent in U.S. Marine Corps recruits (Shaffer, 1997). The incidence among females in these same training programs is higher, ranging from 0.7 percent in the Navy to 9.6 percent in Marine officer candidates. The cost incurred due to stress fractures among 2,000 female Marine recruits is estimated to be $1,850,000 annually with 4,120 lost training days resulting in an extended training period for these women. Thus, it could be projected that the costs to the U.S. Army, a service that trains a greater number of recruits annually, would be substantially higher. Coincidental with the increase in stress fracture incidence was the BCNH subcommittee's concern regarding its possible relationship to the long-term risk of osteoporosis. Because of this higher incidence of stress fractures in female recruits and the resulting increase in length of training time, operating costs, time to military readiness, and the possibility of a shared etiology (or pathogenesis) between short-term (stress fractures) and long-term (osteoporosis) risks to bone health, the DoD, specifically the Headquarters, U.S. Army Medical Research and Materiel Command, requested the BCNH subcommittee to examine this issue and address the following five questions:  Why is the incidence of stress fractures in military basic training greater for women than for men? What is the relationship of genetics and body composition to bone density and the incidence of stress fractures in women? What are the effects of diet, physical activity, contraceptive use, and other lifestyle factors (smoking and alcohol) on the accrual of peak bone mineral content, incidence of stress fractures, and development of osteoporosis in military women?  How do caloric restriction and disordered eating patterns affect hormonal balance and the accrual and maintenance of peak bone mineral content? How can the military best ensure that the dietary intakes of active-duty military women in training and throughout their military careers do not contribute to an increased incidence of stress fractures and osteoporosis?

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The subcommittee decided that in order to address these questions adequately in the short timetable of the proposal, a workshop should be held involving experts in the areas of endocrinology, calcium metabolism, bone mineral assessment, sports medicine, and military nutrition to evaluate the effects of diet, genetics, and physical activity on bone mineral and calcium status. In addition, the report would consider the effects of dietary restriction at the levels observed in military women combined with the physical demands of basic training on short-term bone mineral balance (and the immediate risk of stress fracture) and on the long-term risk of osteoporosis. The BCNH subcommittee believed it was very important to gather as much information as was available from all military services to determine the incidence of stress fractures in women during basic training and the training conditions imposed to assess whether if, among the services, differences in stress fracture incidence would be observed that might be attributed to differences among the training regimens. The subcommittee also believed it was important to evaluate the average level of women's physical fitness at the beginning of training and to evaluate data on nutrient intakes and other lifestyle factors of recruits that were thought to play a role in the pathogenesis of stress fractures. In addition to the military research personnel who presented data to the subcommittee, a liaison group composed of members of the various uniformed services was asked to attend and provide additional information relevant to the topics discussed. Thus, the discussion at the workshop involved experts in various scientific and clinical disciplines, as well as service personnel who dealt with issues of health and physical performance. Military personnel in basic training are subjected to extensive physical conditioning over a relatively short period of time to bring them to the level of fitness required to meet the minimum standards for graduation from basic and/or advanced training programs. Thus, the subcommittee felt it was appropriate to compare the incidence of training injuries (stress fractures) observed in female, civilian competitive athletes with that in military women, given similar training environments. This comparison was deemed relevant because the incidence of athletic amenorrhea, a condition associated with estrogen deficiency and an increased risk of lower bone mineral content, is increased in competitive female athletes. The subcommittee discussed a related but longer-term issue: whether the effect of military training and the military lifestyle (weight management to meet specific weight standards) may be a risk factor for osteoporosis in women in later stages of military service or after retirement. Because the new trainees are largely 18 to 25 years old, no incidence of osteoporosis would be expected in this population. ORGANIZATION OF THE REPORT The BCNH subcommittee's conclusions and recommendations, emanating from the workshop, as well as its review of the relevant literature, are organized around the responses to the five task questions initially submitted by the military. This brief report constitutes an evaluation of the relevant factors provided to the subcommittee at the workshop and subsequent discussions in executive session and forms the response to the task questions and the basis for the subcommittee's conclusions and recommendations.

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Abstracts from the workshop presentations are included in Appendix A of this report and have undergone limited editorial changes, have not been reviewed by the outside group, and represent the views of the individual authors. Because of time constraints, the responses are largely based on data gathered at the workshop, a review of related relevant publications, and the expertise of the subcommittee. ACKNOWLEDGMENTS The subcommittee wishes to acknowledge the help of the IOM's President Kenneth I. Shine, the FNB Division Director Allison A. Yates, and the staff of the BCNH: Study Director Rebecca B. Costello, Staff Officer Sydne J. Carlson-Newberry, Research Assistant Susan M. Knasiak-Raley, Project Assistant Melissa L. Van Doren, and Reports and Information Office Director Michael A. Edington and Associate Claudia M. Carl. Additionally, the subcommittee would like to thank editor Judith Grumstrup-Scott, members of the military liaison panel, and the individuals and organizations who provided information and materials. This report has been reviewed by individuals chosen for their diverse perspectives and technical expertise, in accordance with procedures approved by the NRC's Report Review Committee. The purpose of this independent review is to provide candid and critical comments that will assist the author and the Institute of Medicine in making the published report as sound as possible and to ensure that the report meets institutional standards of objectivity, evidence, and responsiveness to the study charge. The content of the review comments and draft manuscript remain confidential to protect the integrity of the deliberative process. The BCNH subcommittee wishes to thank the following individuals for their participation in the review of this report: Eldon Wayne Askew, Elsworth Buskirk, Mary Jane De Souza, Robert Marcus, Roger McDonald, Alan Rogol, David D. Schnakenberg, and Richard Wood. Although the individuals listed above have provided many constructive comments and suggestions, responsibility for the final content of this report rests solely with the authoring subcommittee and the IOM.

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Contents     EXECUTIVE SUMMARY   1 1   PATHOPHYSIOLOGY AND EPIDEMIOLOGY OF STRESS FRACTURES IN MILITARY WOMEN   9     Essential Concepts   9     Hormonal Regulation of Bone Metabolism and Remodeling   10     Hormones That Regulate Calcium Balance   11     Hormones That Regulate Bone Remodeling   12     Paracrine and Autocrine Factors Involved in Bone Remodeling   13     Pathophysiology of Stress Fractures   14     Bone Loading   14     Accelerated Remodeling   15     Microdamage   16     Diagnosis   17     Epidemiology   17     Military Training Programs   20     Fitness Levels of Recruits   26     Summary   28 2   BONE HEALTH AND RISK FACTORS   29     Bone Mineral Density   30

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    Technical Measurements   31     Bone Markers   31     Bone Mass   32     Genetic Markers   32     Diet   32     Body Composition   35     Physical Activity and Fitness   36     Oral Contraceptives   38     Other Lifestyle Factors   40     Summary   40 3   EFFECTS OF CALORIC INTAKE, PHYSICAL ACTIVITY AND HORMONAL FACTORS ON BONE HEALTH   43     Caloric/Hormonal Factors   43     Effects of Low Energy Intake on Hormonal Levels and Bone Health   44     Effect of Dieting and Weight Loss on Bone Health   45     Incidence of Caloric Restriction and Disordered Eating Patterns in Military Women   46     Hypothalamic Amenorrhea and Bone Health   47     Possible Effects of Excessive Exercise on Bone Health   48     Summary   49 4   CONCLUSIONS AND RECOMMENDATIONS   51     Response to Task Questions   51     Conclusions   54     Recommendations   55     Bone Mass and Bone Health   55     Fitness and Training   55     Reproductive Health and Bone Health   56     Energy Intake and Bone Health   56     Recommendations for Future Research   57     BIBLIOGRAPHY   59     APPENDIXES     A   Workshop Agenda and Abstracts   69 B   Military Recommended Dietary Allowances (AR 40-25, 1985: Chapters 1 and 2)   93 C   Dietary Reference Intakes for Calcium and Related Nutrients (IOM, 1997)   107 D   Biographical Sketches   111 E   Abbreviations   115

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Reducing Stress Fracture in Physically Active Military Women

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