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Systematic review of long term effects of advice to reduce dietary salt in adults

BMJ 2002; 325 doi: (Published 21 September 2002) Cite this as: BMJ 2002;325:628
  1. Lee Hooper (lee.hooper{at}, research fellow in evidence based care and systematic reviewa,
  2. Christopher Bartlett, research associate in health services researchb,
  3. George Davey Smith, professor of clinical epidemiologyb,
  4. Shah Ebrahim, professor in epidemiology of ageingb
  1. a MANDEC, University Dental Hospital of Manchester, Manchester M15 6FH
  2. b Department of Social Medicine, MRC Health Services Research Collaboration, University of Bristol, Bristol BS8 2PR
  1. Correspondence to: L Hooper
  • Accepted 15 May 2002


Objective: To assess the long term effects of advice to restrict dietary sodium in adults with and without hypertension.

Design: Systematic review and meta-analysis of randomised controlled trials.

Data sources: Cochrane library, Medline, Embase, and bibliographies.

Study selection: Unconfounded randomised trials that aimed to reduce sodium intake in healthy adults over at least 6 months. Inclusion decisions, validity and data extraction were duplicated. Random effects meta-analysis, subgrouping, sensitivity analysis, and meta-regression were performed.

Outcomes: Mortality, cardiovascular events, blood pressure, urinary sodium excretion, quality of life, and use of antihypertensive drugs.

Results: Three trials in normotensive people (n=2326), five trials in those with untreated hypertension (n=387), and three trials in people being treated for hypertension (n=801) were included, with follow up from six months to seven years. The large high quality (and therefore most informative) studies used intensive behavioural interventions. Deaths and cardiovascular events were inconsistently defined and reported. There were 17 deaths, equally distributed between intervention and control groups. Systolic and diastolic blood pressures were reduced (systolic by 1.1 mm Hg, 95% confidence interval 1.8 to 0.4 mm Hg; diastolic by 0.6 mm Hg, 1.5 to 0.3 mm Hg) at 13 to 60 months, as was urinary 24 hour sodium excretion (by 35.5 mmol/24 hours, 47.2 to 23.9). Degree of reduction in sodium intake and change in blood pressure were not related.

Conclusions: Intensive interventions, unsuited to primary care or population prevention programmes, provide only small reductions in blood pressure and sodium excretion, and effects on deaths and cardiovascular events are unclear. Advice to reduce sodium intake may help people on antihypertensive drugs to stop their medication while maintaining good blood pressure control.


  • Funding North West Research and Development Training Fellowship (LH).

  • Competing interests LH owns 285 shares in West Indies Rum Distillery, Barbados.

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