Intervention Review

Calcium supplementation for the management of primary hypertension in adults

  1. Heather O Dickinson1,*,
  2. Donald Nicolson2,
  3. Julia V Cook3,
  4. Fiona Campbell4,
  5. Fiona R Beyer5,
  6. Gary A Ford6,
  7. James Mason7

Editorial Group: Cochrane Hypertension Group

Published Online: 19 APR 2006

Assessed as up-to-date: 23 MAY 2006

DOI: 10.1002/14651858.CD004639.pub2


How to Cite

Dickinson HO, Nicolson D, Cook JV, Campbell F, Beyer FR, Ford GA, Mason J. Calcium supplementation for the management of primary hypertension in adults. Cochrane Database of Systematic Reviews 2006, Issue 2. Art. No.: CD004639. DOI: 10.1002/14651858.CD004639.pub2.

Author Information

  1. 1

    Newcastle University, Institute of Health and Society, Newcastle upon Tyne, Tyne & Wear, UK

  2. 2

    University of Leeds, School of Healthcare, Leeds, UK

  3. 3

    Newcastle University , Institute of Health and Society, Newcastle upon Tyne, UK

  4. 4

    University of Sheffield, School of Health and Related Research, Sheffield, UK

  5. 5

    University of Newcastle, Institute for Health and Society, Newcastle upon Tyne, Tyne & Wear, UK

  6. 6

    Royal Victoria Infirmary, Clinical Research Facility, Newcastle upon Tyne, UK

  7. 7

    Durham University, Queen's Campus, School of Medicine and Health, Stockton-on-Tees, UK

*Heather O Dickinson, Institute of Health and Society, Newcastle University, 21 Claremont Place, Newcastle upon Tyne, Tyne & Wear, NE2 4AA, UK. heather.dickinson@newcastle.ac.uk.

Publication History

  1. Publication Status: Edited (no change to conclusions)
  2. Published Online: 19 APR 2006

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Abstract

  1. Top of page
  2. Abstract
  3. Plain language summary

Background

Metabolic studies suggest calcium may have a role in the regulation of blood pressure. Some epidemiological studies reported people with a higher intake of calcium tend to have lower blood pressure. Previous systematic reviews and meta-analyses reached conflicting conclusions about whether oral calcium supplementation can reduce blood pressure.

Objectives

To evaluate the effects of oral calcium supplementation as a treatment for primary hypertension in adults.

Search methods

We searched the Cochrane Library, MEDLINE, EMBASE, Science Citation Index, ISI Proceedings, ClinicalTrials.gov, Current Controlled Trials, CAB abstracts, and reference lists of systematic reviews, meta-analyses and randomised controlled trials (RCTs) included in the review.

Selection criteria

Inclusion criteria were: 1) RCTs comparing oral calcium supplementation with placebo, no treatment, or usual care; 2) treatment and follow-up ≥8 weeks; 3) participants over 18 years old, with raised systolic blood pressure (SBP) ≥140 mmHg or diastolic blood pressure (DBP) ≥85 mmHg; 4) SBP and DBP reported at end of follow-up. We excluded trials where: participants were pregnant; received antihypertensive medication which changed during the study; or calcium supplementation was combined with other interventions.

Data collection and analysis

Two reviewers independently abstracted data and assessed trial quality. Disagreements were resolved by discussion or a third reviewer. Random effects meta-analyses and sensitivity analyses were conducted.

Main results

We included 13 RCTs (n=485), with between eight and 15 weeks follow-up. The results of the individual trials were heterogeneous. Combining all trials, participants receiving calcium supplementation as compared to control had a statistically significant reduction in SBP (mean difference: -2.5 mmHg, 95% CI: -4.5 to -0.6, I2 = 42%), but not DBP (mean difference: -0.8 mmHg, 95% CI: -2.1 to 0.4, I2 = 48%). Sub-group analyses indicated that heterogeneity between trials could not be explained by dose of calcium or baseline blood pressure. Heterogeneity was reduced when poor quality trials were excluded. The one trial reporting adequate concealment of allocation and the one trial reporting adequate blinding yielded results consistent with the primary meta-analysis.

Authors' conclusions

Due to poor quality of included trials and heterogeneity between trials, the evidence in favour of causal association between calcium supplementation and blood pressure reduction is weak and is probably due to bias. This is because poor quality studies generally tend to over-estimate the effects of treatment. Larger, longer duration and better quality double-blind placebo controlled trials are needed to assess the effect of calcium supplementation on blood pressure and cardiovascular outcomes.

 

Plain language summary

  1. Top of page
  2. Abstract
  3. Plain language summary

Calcium supplementation for the management of primary hypertension in adults

This review did not find robust evidence that oral calcium supplementation reduces high blood pressure in adults. It reviewed 13 trials enrolling 485 people, which compared calcium supplementation with placebo or no treatment, and measured blood pressure 8 to 15 weeks later. On average, people receiving extra calcium achieved slightly lower systolic blood pressure at the end of trials. However, most trials were of poor quality, so their results may not be reliable. Trials were too small and short to measure whether extra calcium reduces the risk of death, heart attack or stroke. Calcium usually had no more adverse effects than placebo. Larger, longer duration, better quality trials are needed to clarify whether calcium supplementation can lower high blood pressure.