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Hydration-Monograph.Pdf Hydration: Fluids for Life Monograph ILSI North America Series Ann C. Grandjean Sheila M. Campbell Hydration cover 2.indd 2 9/14/2004 12:18:25 PM Hydration: ILSI North America Fluids for Life A Monograph by the North American Branch of the International Life Sciences Institute Ann Grandjean, EdD, FACN, CNS Sheila Campbell, PhD, RD i Hydration layout one.indd 1 9/15/2004 3:09:11 PM © 2004 ILSI North America All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or trans- mitted, in any form or by any means, electronic, mechanical, photocopying, record- ing, or otherwise, without the prior written permission of the copyright holder. The International Life Sciences Institute –North American Branch (ILSI NA) does not claim copyright in U.S. Government information. Authorization to photocopy items for internal or personal use is granted by ILSI for libraries and other users registered with the Copyright Clearance Center (CCC) Transactional Reporting Services, provided that $0.50 per copy per page is paid directly to CCC, 222 Rosewood Drive, Danvers, MA 01923. (508) 750-8400. The use of trade names and commercial sources in this document is for purposes of identification only, and does not imply endorsement by ILSI North America. In addition, the views expressed herein are those of the individual authors and/or their organizations, and do not necessarily reflect those of ILSI North America. ILSI North America One Thomas Circle, NW, Ninth Floor Washington, DC 20005 ISBN 1-57881-182-1 Printed in the United States of America ii Hydration layout one.indd 2 9/15/2004 3:09:11 PM Contents Foreword _____________________________________________ v About ILSI and ILSI North America ________________________vi Acknowledgments _____________________________________ vii Hydration — Fluids for Life ______________________________ 1 Appendix A __________________________________________ 29 Appendix B __________________________________________ 30 References ___________________________________________ 32 iii Hydration layout one.indd 3 9/15/2004 3:09:11 PM iv Hydration layout one.indd 4 9/15/2004 3:09:12 PM FOREWORD Poets have called water the elixir of life. Scientists and clinicians, who are more pragmatic and less dramatic, call water a nutrient. Poets’ depiction may in fact be more appropriate, as water is second only to oxygen as essential to life. As stated in an ancient proverb: “Thousands have A man can live three weeks without food, three days without water, lived without love, not but only three minutes without air. one without water.” After we assumed for years that our thirst would ensure sufficient W. H. Auden water intake, we are beginning to appreciate the impact of body water, and the balance thereof, and recognize the detriments of (1907-1973) reduced body water and electrolyte imbalances. The incidence of deaths in otherwise healthy young adults, the increased awareness of dehydration in nursing home residents, and other recent research findings about type and amount of fluids that support hydration increase the value of this monograph. The Lead Review Article published in Nutrition Reviews in August 2003, reviewed by the ILSI North America Project Committee on Hydration, provides a comprehensive, albeit brief, overview of pertinent aspects of hydration. For the most part, the review article is current. However, the recent publication of the Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate (Food and Nutrition Board [FNB] 2004) renders the section on recom- mended intakes obsolete. Additionally, due to space, the coverage of some topics, especially basic physiology and population-specific information, is limited. Therefore, the ILSI North America Project Committee on Hydration commissioned this concise monograph. This monograph provides readers with an overview of current knowledge related to the functions of water, methods of determin- ing hydration status, sources of water in the diet, and specific considerations for infants, children, physically active individuals, and the elderly. Recommended intakes, as specified by the FNB in the 2004 Dietary Reference Intakes for water, are also covered. For additional reading and more detailed explanations of the informa- tion herein, a list of references is provided. v Hydration layout one.indd 5 9/15/2004 3:09:12 PM About ILSI and ILSI North America The International Life Sciences Institute (ILSI) is a nonprofit, worldwide foundation based in Washington, D.C. established in 1978 to advance the understanding of scientific issues relat- ing to nutrition, food safety, toxicology, risk assessment, and the environment. ILSI branches include Argentina, Brasil, Europe, India, Japan, Korea, Mexico, North Africa and Gulf Region, North America, North Andean, South Africa, South Andean, Southeast Asia Region, the Focal Point in China, and the ILSI Health and Environmental Sciences Institute. ILSI also accomplishes its work through the ILSI Research Foundation (composed of the ILSI Hu- man Nutrition Institute and the ILSI Risk Science Institute) and the ILSI Center for Health Promotion. The North American branch of the International Life Sciences Institute (ILSI N.A.) is a public, non-profit scientific foundation. ILSI N.A. advances the understanding and application of scientific issues related to the nutritional quality and safety of the food sup- ply, as well as health issues related to consumer self-care products. The organization carries out its mission by sponsoring relevant research programs, professional education programs and work- shops, seminars, and publications, as well as providing a neural forum for government, academic, and industry scientists to discuss and resolve scientific issues of common concern for the well-being of the general public. ILSI N.A.’s programs are supported primarily by its industry membership. For more information, visit www.ilsi.org vi Hydration layout one.indd 6 9/15/2004 3:09:12 PM Acknowledgements This monograph was created with the support of the ILSI N.A. Project Committee on Hydration. The committee was established in 2001 to investigate broad issues of hydration including the scien- tific understanding of adequate hydration sources, the fluid/disease relationship, and the role of foods and beverages in maintaining hydration. The committee is grateful for the invaluable support of scientific advisors Dr. Ann Grandjean, UNMC Center for Human Nutrition and Dr. Suzie Harris, ILSI Human Nutrition Institute. The commit- tee wishes to express its sincere thanks to Dr. Sheila Campbell for her valuable contribution in the writing of the document. The com- mittee also wishes to convey its great appreciation and gratitude to Dr. Ann Grandjean as main author of the document. The commit- tee is also appreciative of the dedicated work of committee chair Dr. Maxime Buyckx, The Coca-Cola Company, and Ms. Heather Hartland Steele, committee manager. vii Hydration layout one.indd 7 9/15/2004 3:09:12 PM viii Hydration layout one.indd 8 9/15/2004 3:09:12 PM Hydration – Fluids for Life Water is by far the most abundant substance on earth and in our bodies. For example, approximately six pounds of an eight-pound baby is water. Water is not only abundant, it is essential to life, as all metabolic processes occur in a water medium. This monograph reviews the functions and distribution of water throughout the body, describes imbalances that occur, presents current recommendations for water consumption, and delineates and describes age-specific issues. Functions and Distribution of Body Water Water, because of its many properties, performs numerous distinct and vital bodily functions. Instrumental properties of water include the following. • Water transports nutrients to cells, wastes from cells, and substanc- es, such as hormones, enzymes, blood platelets, and blood cells. As such, it facilitates cellular metabolism and proper cellular chemical functioning. • Water is an excellent solvent and suspending medium. Many sub- strates dissolve or become suspended in water, and thus can react to form new compounds. This attribute of water also facilitates excre- tion of waste products and toxins in urine. • Water, the solvent, combines with viscous molecules to form lu- bricating fluids for joints, mucous that lubricates the digestive and genitourinary tracts, serous fluid that lubricates the viscera, and saliva and other secretions that lubricate food as it passes through the digestive tract. • Water absorbs heat with relatively little change in water tempera- ture. Because of this heat-storing ability, water helps regulate body temperature by absorbing heat and releasing it through production and evaporation of perspiration. 1 Hydration layout one.indd 1 9/15/2004 3:09:13 PM • Water is an important structural unit in the body. It maintains cel- lular shape, is an integral part of cell membranes, cushions organs, and helps maintain body structures. The amount of water in the human body, commonly called total body water (TBW), varies due to age, sex, muscularity, and adipos- ity. In healthy individuals, TBW changes little except as a result of growth, weight gain, weight loss, or conditions such as pregnancy and lactation. The amount of TBW does vary significantly however from individual to individual due to a variety of factors. Fat-free mass in adults is approximately 70% to 75% water, while adipose tissue is approximately 10% to 40% water. Accordingly, women tend to have a lower percent of body water than men because of a relatively higher percentage of fat. With increasing adiposity, the water portion of adipose tissue decreases (Laaksonen 2003). As we age, total body water (TBW) decreases primarily due to loss of muscle mass (Rose 2001). For example, if female, the newborn who is 74% water at birth will be 47% water by age 51; if male, 56% at the same age. Table 1 demonstrates the impact of age and gender on TBW. Effectively, TBW is distributed between two compartments. All fluids outside the cells are collectively referred to as extracellular fluid (ECF), while water inside cells is called intracellular fluid (ICF). ECF is further divided into three compartments.
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