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Meta-Analysis
. 2011 Jul 6:(7):CD009217.
doi: 10.1002/14651858.CD009217.

Reduced dietary salt for the prevention of cardiovascular disease

Rod S Taylor  1 , Kate E Ashton, Tiffany Moxham, Lee Hooper, Shah Ebrahim
Affiliations
Meta-Analysis

Reduced dietary salt for the prevention of cardiovascular disease

Rod S Taylor et al. Cochrane Database Syst Rev. .

Update in

Abstract

Background: An earlier Cochrane review of dietary advice identified insufficient evidence to assess effects of reduced salt intake on mortality or cardiovascular events.

Objectives: 1. To assess the long term effects of interventions aimed at reducing dietary salt on mortality and cardiovascular morbidity.2. To investigate whether blood pressure reduction is an explanatory factor in any effect of such dietary interventions on mortality and cardiovascular outcomes.

Search strategy: The Cochrane Library (CENTRAL, Health Technology Assessment (HTA) and Database of Abstracts of Reviews of Effect (DARE)), MEDLINE, EMBASE, CINAHL and PsycInfo were searched through to October 2008. References of included studies and reviews were also checked. No language restrictions were applied.

Selection criteria: Trials fulfilled the following criteria: (1) randomised with follow up of at least six-months, (2) intervention was reduced dietary salt (restricted salt dietary intervention or advice to reduce salt intake), (3) adults, (4) mortality or cardiovascular morbidity data was available. Two reviewers independently assessed whether studies met these criteria.

Data collection and analysis: Data extraction and study validity were compiled by a single reviewer, and checked by a second. Authors were contacted where possible to obtain missing information. Events were extracted and relative risks (RRs) and 95% CIs calculated.

Main results: Seven studies (including 6,489 participants) met the inclusion criteria - three in normotensives (n=3518), two in hypertensives (n=758), one in a mixed population of normo- and hypertensives (n=1981) and one in heart failure (n=232) with end of trial follow-up of seven to 36 months and longest observational follow up (after trial end) to 12.7 yrs. Relative risks for all cause mortality in normotensives (end of trial RR 0.67, 95% CI: 0.40 to 1.12, 60 deaths; longest follow up RR 0.90, 95% CI: 0.58 to 1.40, 79 deaths) and hypertensives (end of trial RR 0.97, 95% CI: 0.83 to 1.13, 513 deaths; longest follow up RR 0.96, 95% CI; 0.83 to 1.11, 565 deaths) showed no strong evidence of any effect of salt reduction. Cardiovascular morbidity in people with normal blood pressure (longest follow-up RR 0.71, 95% CI: 0.42 to 1.20, 200 events) or raised blood pressure at baseline (end of trial RR 0.84, 95% CI: 0.57 to 1.23, 93 events) also showed no strong evidence of benefit. Salt restriction increased the risk of all-cause death in those with congestive heart failure (end of trial relative risk: 2.59, 95% 1.04 to 6.44, 21 deaths). We found no information on participants health-related quality of life.

Authors' conclusions: Despite collating more event data than previous systematic reviews of randomised controlled trials (665 deaths in some 6,250 participants), there is still insufficient power to exclude clinically important effects of reduced dietary salt on mortality or cardiovascular morbidity in normotensive or hypertensive populations. Further RCT evidence is needed to confirm whether restriction of sodium is harmful for people with heart failure. Our estimates of benefits from dietary salt restriction are consistent with the predicted small effects on clinical events attributable to the small blood pressure reduction achieved.

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Figures

Figure 1
Figure 1
Study flow diagram
Figure 2
Figure 2
Risk of bias graph: review authors’ judgements about each risk of bias item presented as percentages across all included studies.
Figure 3
Figure 3
Risk of bias summary: review authors’ judgements about each risk of bias item for each included study.
See this image and copyright information in PMC

Comment in

References

References to studies included in this review

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    1. *

    2. Hypertension Prevention Trial Research Group The Hypertension Prevention Trial: three-year effects of dietary changes on blood pressure. Archives of Internal Medicine. 1990;150:153–62. - PubMed

References to studies excluded from this review

    1. Bentley BB. Dietary sodium in heart failure. University of Kentucky; USA: 2006.
    1. Knuist M, Bonsel GJ, Zondervan HA, Treffers PE. Low sodium diet and pregnancy-induced hypertension: a multicentre randomised controlled trial. British Journal of Obstetrics and Gynaecology. 1998;105:430–4. - PubMed
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    1. Licata G, Di Pasquale P, Parrinello G, Cardinale A, Scandurra A, Follone G, et al. Effects of high-dose furosemide and small-volume hypertonic saline solution infusion in comparison with a high dose of furosemide as bolus in refractory congestive heart failure: Long-term effects. American Heart Journal. 2003;145:459–66. - PubMed
    1. van der Post JA, van Buul BJ, Hart AA, van Heerikhuize JJ, Pesman G, Legros JJ, et al. Vasopressin and oxytocin levels during normal pregnancy: effects of chronic dietary sodium restriction. Journal of Endocrinology. 1997;152:345–54. - PubMed

Additional references

    1. Alderman MH. Reducing dietary sodium. The case for caution. JAMA. 2010;303:448–9. - PubMed
    1. Allender S, Scarborough P, Peto V, Rayner M, Leal J, Luengo-Fernandez R, et al. European Cardiovascular Disease Statistics 2008. 3rd Edition European Heart Network; 2008.
    1. Alli C, Avanzini F, Bettelli G, Bonati M, Colombo F, Corso R, et al. Feasibility of a long-term low-sodium diet in mild hypertension. Journal of Human Hypertension. 1992;6:281–6. - PubMed
    1. Arroll B, Beaglehole R. Salt restriction and physical activity in treated hypertensives. New Zealand Medical Journal. 1995;108:266–8. - PubMed
    1. Cappuccio FP. Sodium, potassium, calcium and magnesium and cardiovascular risk. J Cardiovasc Risk. 2000;7:1–3. - PubMed

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