Nutrition A health promotion approach This page intentionally left blank Nutrition A health promotion approach 3rd Edition Geoffrey P WebbBSC, MSC, PHD Senior Lecturer in Nutrition and Physiology, University of East London, London, UK First published in Great Britian in 1994 by Butterworth Heinemann Second edition 2002 by Hodder Arnold,an imprint of Hodder Education This third edition published in 2008 by HodderArnold,animprintofHodderEducation,anHachetteUKCompany, 338 Euston Road,London NW1 3BH http://www.hoddereducation.com © 2008 Geoffrey P Webb All rights reserved.Apart from any use permitted under UK copyright law, this publication may only be reproduced,stored or transmitted,in any form, or by any means with prior permission in writing of the publishers or in the case of reprographic production in accordance with the terms of licences issued by the Copyright Licensing Agency.In the United Kingdom such licences are issued by the Copyright Licensing Agency:Saffron House,6-10 Kirby Street,London EC1N 8TS. 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British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library Library of Congress Cataloging-in-Publication Data A catalog record for this book is available from the Library of Congress ISBN 978-0-340-93882-9 2345678910 Commissioning Editor: Jo Koster/Naomi Wilkinson Project Editor: Clare Patterson Production Controller: Andre Sim Cover Designer: Helen Townson Typeset in 9.5/12 Berling Roman by Charon Tec Ltd (A Macmillan Company) www.charontec.com Printed and bound in Spain What do you think about this book? Or any other Hodder Arnold title? Please visit our website:www.hoddereducation.com For my parents Maisie and William who made many personal sacrifices to ensure my education and for daughter Katherine and my wife Susan for their patience and support during the writing of this book. This page intentionally left blank Contents Preface xi PART 1 CONCEPTS AND PRINCIPLES 1 1 Changing priorities for nutrition education 3 Identification of the essential nutrients 3 Adequacy: the traditional priority in nutrition 5 The new priority: diet as a means to health promotion or disease prevention 7 Is intervention to induce dietary change justified? 16 Effecting dietary change 22 Concluding remarks 28 2 Food selection 29 Introduction and aims of the chapter 29 The biological model of food 30 Dietary and cultural prejudice 31 Food classification systems 32 Non-nutritional uses of food 36 The hierarchy of human needs 38 A model of food selection: the hierarchy of availabilities model 39 Physical availability 41 Economic availability 42 Cultural availability 54 ‘Gatekeeper’ limitations on availability 60 3 Methods of nutritional surveillance and research 63 Introduction and aims of the chapter 63 Nutritional assessment and surveillance 63 Methods used to establish links between diet and disease 97 4 Dietary guidelines and recommendations 123 The range of ‘expert reports’ and their consistency 123 Variations in the presentation of guidelines and recommendations 125 ‘Food’ recommendations 127 Energy and body weight 128 Recommendations for fats, carbohydrates, protein and salt 128 Alcohol 130 viii Contents How do current UK diets compare with ‘ideal’ intakes? 133 Other nutrients 134 Willingness to change 134 Some barriers to dietary change 136 Aids to food selection 137 Concluding remarks 141 5 Cellular energetics 143 Introduction and aims of the chapter 143 Overview of metabolism 143 Metabolism of glucose and the monosaccharides 145 Metabolism of fatty acids and glycerol 147 Metabolism of amino acids 148 The pentose phosphate pathway 148 An overview of macronutrient handling in the gut 149 PART 2 ENERGY, ENERGY BALANCE AND OBESITY 151 6 Introduction to energy aspects of nutrition 153 Sources of energy 153 Units of energy 153 How are energy requirements estimated? 153 Variation in average energy requirements: general trends 156 Energy content of foods 157 Sources of dietary energy by nutrient 157 Energy density 159 Nutrient density 162 The sources of dietary energy by food groups 162 Starvation 163 Eating disorders 167 Cancer cachexia 170 7 Energy balance and its regulation 173 Concept of energy balance 173 Is there physiological regulation of energy balance? 174 ‘Set point’ theory 175 Is energy expenditure regulated? 175 External influences that affect food intake 178 Control of energy intake 178 8 Obesity 187 Defining obesity 187 Prevalence of obesity 187 Consequences of obesity 194 The metabolic syndrome or ‘syndrome X’ 201 Causes of obesity 201 Prevention and treatment of obesity in populations 210 Obesity treatment in individuals 213 More ‘aggressive’ treatments for obesity 217 Contents ix PART 3 THE NUTRIENTS 223 9 Carbohydrates 225 Introduction 225 Nature and classification of carbohydrates 226 Dietary sources of carbohydrate 227 Sugars 228 Artificial sweeteners 230 Diet and dental health 232 Starches 235 Non-starch polysaccharide 237 Resistant starch 240 The glycaemic index 241 Does dietary fibre/non-starch polysaccharide protect against bowel cancer and heart disease? 241 Possible mechanisms by which diet may influence the risk of bowel cancer and heart disease 245 10 Protein and amino acids 247 Traditional scientific aspects of protein nutrition 247 Significance of protein in human nutrition 255 Concluding remarks 261 11 Fat 263 Nature of dietary fat 263 Types of fatty acids 264 Sources of fat in the diet 269 Roles of fat in the diet 272 Blood lipoproteins 278 Digestion, absorption and transport of dietary lipids 279 Transport of endogenously produced lipids 280 The diet–heart hypothesis 282 Current ‘health images’ of different dietary fats 284 The key tenets of the diet–heart hypothesis 289 Review of the evidence for the diet–heart hypothesis 289 Fish oils 295 Other natural oils used as supplements 299 12 The micronutrients 301 Scope of this chapter 301 Overview of dietary supplements 302 General micronutrient adequacy of British adults 303 Antioxidants and the oxidant theory of disease 308 Do high antioxidant intakes prevent heart disease, cancer and other chronic diseases? 313 Use of substances other than essential nutrients as dietary supplements 318 13 The vitamins 329 Some general concepts and principles 329 The individual vitamins 332