Salt and Health Scientific Advisory Committee on Nutrition 2003 The Stationery Office ©Crown Copyright 2003. Published for the Food Standards Agency and the Department of Health under licence from the Controller of Her Majesty’s Stationery Office. Applications for reproduction should be made in writing to The Copyright Unit, HerMajesty’s Stationery Office, St Clements House, 2-16 Colegate, Norwich NR3 1BQ ISBN 0 11 243075 9 Published by TSO (The Stationery Office) and available from: Online www.tso.co.uk/bookshop Mail, Telephone, Fax & E-mail TSO PO Box 29, Norwich NR3 1GN Telephone orders/General enquiries: 0870 600 5522 Order through the Parliamentary Hotline Lo-call 0845 7 023474 Fax orders: 0870 600 5533 E-mail: [email protected] Textphone 0870 240 3701 TSO Shops 123 Kingsway, London WC2B 6PQ 020 7242 6393 Fax 020 7242 6394 68-69 Bull Street, Birmingham B4 6AD 0121 236 9696 Fax 0121 236 9699 9-21 Princess Street, Manchester M60 8AS 0161 834 7201 Fax 0161 833 0634 16 Arthur Street, Belfast BT1 4GD 028 9023 8451 Fax 028 9023 5401 18-19 High Street, Cardiff CF10 1PT 029 2039 5548 Fax 029 2038 4347 71 Lothian Road, Edinburgh EH3 9AZ 0870 606 5566 Fax 0870 606 5588 TSO Accredited Agents (see Yellow Pages) and through good booksellers Further copies may be obtained from the SACN website at www.sacn.gov.uk or telephone the SACN Secretariat at Tel: 020 7972 1364, 020 7276 8926 Scientific Advisory Committee on Nutrition Preface High blood pressure is common in the UK. It is a major risk factor for cardiovascular disease and premature death. Reducing the average salt intake of the population is likely to decrease the burden of high blood pressure and improve public health. Sodium is an essential nutrient and salt is the major source of sodium in the UK diet. Most people, however, consume more sodium than is required. The latest available data show that habitual levels of salt intake are high for both adults and children. For adults, average intake is two and a half times the reference nutrient intake for sodium. Although accurate data are not available for children, conservative estimates indicate that, on a body weight basis, the average salt intake of children is higher than that of adults. In 1994, the Committee on Medical Aspects of Food and Nutrition Policy (COMA), in a review of nutritional aspects of cardiovascular disease, made a recommendation to reduce the average salt intake of the population from 9g/day to 6g/day which has also been endorsed by the Chief Medical Officer of England. The present report has been prepared in response to a request, from the Food Standards Agency and the Chief Medical Officer of Wales, for a risk assessment of salt by the Scientific Advisory Committee on Nutrition (SACN). The evidence published since 1994 has been appraised, in a methodological fashion, to assess whether the previous recommendation to reduce salt intakes in the population remains valid. It is the first time that an expert committee has specifically undertaken a review of the evidence on salt and health in the UK. i Scientific Advisory Committee on Nutrition There is now a larger body of evidence, which draws an association between salt consumption and blood pressure. SACN has concluded that the habitual salt intake of the population raises the risk of high blood pressure, which in turn increases the risk of stroke and premature death from cardiovascular diseases. The risk increases with age and is not simply a feature of those with the highest salt intakes or the highest levels of blood pressure but graded and evident across a range of salt intakes that are habitual in the UK. The report accepts the previous recommendation for a reduction in the population average intake of salt to 6g per day for adults and for the first time has set targets for children which are proportionate to their needs. Meeting these targets would be of major benefit to public health. Even a small reduction in salt intake could help to reduce the burden of high blood pressure in our population. A public health approach to reducing salt levels is required. A targeted approach to salt reduction by health professionals dealing with patients with diagnosed hypertension, by itself, may not be enough. The draft of this report was made available for comment and I thank all those who responded. The comments were carefully considered during finalisation of the report. The responsibility of SACN is for an assessment of risk. Many of the comments received during the consultation related to the management or communication of risk, and hence were outside the remit of the committee. ii Scientific Advisory Committee on Nutrition It is for the Government to consider the action required to achieve the recommended reductions in the salt intake of the population. Achieving these targets will not be easy, as a substantial reduction in salt intake is required. This will entail a sustained, gradual reduction in the salt content of food over a number of years. Most salt in the diet does not come from addition to food in the home by consumers but from processed foods. This makes it extremely difficult for individuals to reduce their own salt intake and to maintain a reduced intake over any length of time. Key to achieving a sustained salt reduction for public health benefit is the engagement of the food industry (manufacturers, retailers and caterers). All consumers, including children, need more information on salt and sodium, particularly on the adverse health effects of excessive salt consumption, to enable them to make healthy dietary choices and reduce salt in their diet. The Committee also identified the need for improving the existing evidence base, which might facilitate salt reduction strategies, particularly on: • how patterns of salt intake vary across and within groups of the population; • the contribution home prepared meals and foods eaten outside the home make to overall salt intakes in the UK; • the processing techniques and new technologies that can help to reduce salt content of foods whilst maintaining safety and palatability. iii Scientific Advisory Committee on Nutrition The potential public health rewards of salt reduction at a population level through lowering the salt content of manufactured foods has international support. There is compelling evidence that this is an effective and appropriate means to reduce the public health burden of cardiovascular disease to society and the risk of ill health to individuals. Professor Alan Jackson Chair of the Scientific Advisory Committee on Nutrition April 2003 iv Scientific Advisory Committee on Nutrition Contents Page Preface i Membership of Scientific Advisory Committee onNutrition: Salt Subgroup ix Membership of Scientific Advisory Committee onNutrition x Summary 1 1 Scientific Advisory Committee on Nutrition: Saltand Health 5 Background 5 Terms of reference 5 Methodology 6 2 Introduction 8 Dietary exposure to salt 8 Current recommendations 11 Current Government position 12 Current initiatives to reduce the salt content of processed foods 13 3 Public Health Issues 14 Blood pressure 14 Hypertension 14 Prevalence of hypertension in the UK 16 Population approach to blood pressure reduction 17 Other outcomes 18 v Scientific Advisory Committee on Nutrition 4 Review of the Evidence Since 1994 19 Physiological requirements for sodium 19 Summary and conclusions 24 Salt sensitivity 24 Prevalence of salt sensitivity 26 Salt sensitivity as an independent predictor ofcardiovascular events 26 Summary and conclusions 27 Evidence for an association between salt intake and blood pressure 28 Animal studies 28 Human epidemiological studies 30 Cross-sectional studies 30 Intervention studies 31 – Dietary manipulation 31 – Dietary advice 35 – Meta-analyses of intervention trials 36 Summary and conclusions 37 Morbidity and premature mortality 39 Animal studies 39 Human studies 39 Cardiovascular disease 39 – Cross-sectional studies 39 – Prospective studies 40 Other outcomes 42 – Left ventricular hypertrophy 42 – Bone health 43 Summary and conclusions 44 vi Scientific Advisory Committee on Nutrition 5 The Role of Other Factors in the Development of Hypertension 45 Other dietary factors 45 Alcohol 46 Body weight 46 Physical activity 47 Genetic predisposition 47 Summary and conclusions 48 6 Infants and Children 49 Physiological requirements for sodium 49 Blood pressure 50 Body weight 52 Early life experience 53 Summary and conclusions 54 7 Research Recommendations 56 8 Conclusions 57 References 60 Annexes 1. Responses received by SACN to the call for submissions on salt 71 2. Working procedures 73 3. Main sources of sodium from food 95 4. Dietary reference values for sodium 99 5. Average blood pressures for men and women in England, Scotland and Northern Ireland 101 6. Overview of sodium metabolism and regulation 103 vii Scientific Advisory Committee on Nutrition 7. Sodium sensitivity: methods and criteria 105 8. Design of studies since 1994 examining theeffects of salt and blood pressure onmorbidity and mortality 107 9. Meta-analyses and systematic reviews published since 1994 on salt and blood pressure 115 viii