Primary Care

Randomised controlled factorial trial of dietary advice for patients with a single high blood pressure reading in primary care

BMJ 2004; 328 doi: (Published 29 April 2004) Cite this as: BMJ 2004;328:1054
  1. Paul Little (psl3{at}, professor of primary care research1,
  2. Jo Kelly, research assistant1,
  3. Jane Barnett, research nurse1,
  4. Martina Dorward, research nurse1,
  5. Barrie Margetts, senior lecturer in public health nutrition2,
  6. Daniel Warm, lecturer in public health nutrition2
  1. 1University of Southampton, Division of Community Clinical Sciences, Primary Medical Care Group, Southampton SO16 5ST
  2. 2Public Health Nutrition, University of Southampton, Community Clinical Sciences Division, Southampton General Hospital, Southampton, SO16 6YD
  1. Correspondence to: P Little
  • Accepted 18 February 2004


Objective To assess the effect of brief interventions during the “watchful waiting” period for hypertension.

Design Factorial trial.

Setting General practice.

Methods 296 patients with blood pressure > 160/90 mm Hg were randomised to eight groups defined by three factors: an information booklet; low sodium, high potassium salt; prompt sheets for high fruit, vegetable, fibre; and low fat.

Main outcome measures Blood pressure (primary outcome); secondary outcomes of diet, weight, and dietary biomarkers (urinary sodium:potassium (Na:K) ratio; carotenoid concentrations).

Results Blood pressure was not affected by the booklet (mean difference (diastolic blood pressure) at one month 0.2, 95% confidence interval 1.6 to 2.0), salt (0.13; 1.7 to 2.0), or prompts (0.52; 1.3 to 2.4). The salt decreased Na:K ratio (difference 0.32; 0.08 to 0.56, P = 0.01), and the prompts helped control weight (difference 0.39 (0.85 to 0.05) kg at one month, P = 0.085; 1.2 (0.1 to 2.25) kg at six months, P = 0.03). Among those with lower fruit and vegetable consumption (< 300 g per day), prompts increased fruit and vegetable consumption and also carotenoid concentrations (difference 143 (16 to 269) mmol/l, P < 0.03) but did not decrease blood pressure.

Conclusion During watchful waiting, over and above the effect of brief advice and monitoring, an information booklet, lifestyle prompts, and low sodium salt do not reduce blood pressure. Secondary analysis suggests that brief interventions—particularly lifestyle prompts—can make useful changes in diet and help control weight, which previous research indicates are likely to reduce the long term risk of stroke.


  • Contributors PL had the original idea for this research, which was developed by PL, BM, and DW. JB and MD managed patients, and with JK further developed the protocol and ran the study on a day to day basis. PL and BM analysed the data. All authors contributed to writing the paper. PL is guarantor.

  • Funding British Heart Foundation

  • Conflict of interest None declared.

  • Ethical approval Southampton and South West Hampshire local research ethics committee.

  • Accepted 18 February 2004
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