Intended for healthcare professionals


Long term effects of advice to reduce dietary salt

BMJ 2003; 326 doi: (Published 25 January 2003) Cite this as: BMJ 2003;326:222

Front cover was highly misleading

  1. Graham A MacGregor, professor of cardiovascular medicine,
  2. Feng J He, cardiovascular research fellow
  1. Blood Pressure Unit, St George's Hospital Medical School, London SW17 0RE
  2. Department of Epidemiology and Public Health, Distillery House, University College Cork
  3. Department of Environmental and Preventive Medicine, Wolfson Institute of Preventive Medicine, Barts and the London, Queen Mary's School of Medicine and Dentistry, Queen Mary, University of London, London EC1M 6BQ
  4. MANDEC, University Dental Hospital of Manchester, Manchester M15 6FH
  5. MRC Health Services Research Collaboration
  6. Department of Social Medicine, University of Bristol, Bristol BS8 2PR

    EDITOR—That small reductions in salt intake (2 g/day) have a small but significant effect on blood pressure is hardly surprising.1 Nevertheless, in populations this would have a large effect on reducing strokes, heart attacks, and heart failure.

    Hooper et al do not ask why reducing salt intake in the long term is so difficult. They claim that the interventions used were intensive, but most studies gave no details about what advice was offered. Furthermore, 75% of salt intake comes from processed food.2 This needs to be avoided or contain less salt. None of the studies provided reduced salt foods.

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    Interpreting the study by Hooper et al is not helped by the editor writing the front cover of the BMJ, who seems to have read a different paper and misinterpreted the important positive findings. The confusion is increased by the authors' press release,3 which rightly blames the difficulty in reducing salt intake squarely on the food industry.

    This confusion is compounded by errors in the meta-analysis. For example, the 18 month TOPH trial (phase I) was included as an intervention trial over “60 months,” but salt intake was reduced for only 18 months, after which all participants returned to their normal diet. References were misquoted, and the correspondence following these papers was ignored. The totality of evidence for reducing salt is stronger than for any other non-pharmacological treatment.

    Ninety five per cent of the population are at risk of developing cardiovascular disease,4 and 40% die from it. There are no controlled trials showing a reduction in mortality on stopping smoking, reducing fat intake alone (without fish oil supplements), reducing salt intake, losing weight, increasing fruit and vegetable consumption, or increasing exercise. For most of these factors no attempt has been made to conduct long term trials, …

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