BACKGROUND AND PURPOSE:

• Several studies have found a link between increased calcium levels and reduced blood pressure
• In this update to a 2015 review, Cormick et al. (Cochrane Database of Systematic Reviews, 2021) assessed the efficacy and safety of calcium supplementation versus placebo/control for reducing blood pressure in normotensive people and for the prevention of primary hypertension

METHODS:

• Update to a systematic review and meta-analysis
• Inclusion criteria
  • Randomized and quasi-randomized controlled trials
  • Studies that included normotensive people and provided dietary calcium interventions such as
    • Supplementation (pills, tablets or sprinkle powder)
    • Food fortification
    • Placebo/control
• Study design
  • GRADE criteria used to assess the certainty of evidence
• Primary outcomes
  • Hypertension: BP ≥140/90 mmHg)
  • Blood pressure measures

RESULTS:

• 20 trials (18 in meta-analysis) | 3512 participants (3140 in meta-analysis)
  • New trials included in update: 4
• Calcium interventions had a significant reduction effect on systolic and diastolic blood pressure
  • Systolic
    • Mean difference (MD) ‐1.37 mmHg (95% CI, ‐2.08 to ‐0.66)
    • 3140 participants; 18 studies; high‐certainty evidence
  • Diastolic
    • MD ‐1.45 (95% CI, ‐2.23 to -0.67)
    • 3039 participants; 17 studies; high‐certainty evidence

Reduction Based on Age

• <35 years
  • Systolic
    • MD ‐1.86 (95% CI, ‐3.45 to ‐0.27)
    • 452 participants; 8 studies; moderate‐certainty evidence
  • Diastolic
    • MD ‐2.50 (95% CI ‐4.22 to ‐0.79)
    • 351 participants; 7 studies; moderate‐certainty evidence
• ≥35 years
  • Systolic
    • MD ‐0.97 (95% CI, ‐1.83 to ‐0.10)
    • 2688 participants; 10 studies; I² = 0%, high‐certainty evidence
  • Diastolic
    • MD ‐0.59 (95% CI, ‐1.13 to ‐0.06)
    • 2688 participants; 10 studies; I² = 0%, high‐certainty evidence

Reduction in Both Women and Men

• Women
  • Systolic
    • MD ‐1.25 (95% CI, ‐2.53 to 0.03)
    • 1915 participants; 8 studies; high‐certainty evidence
  • Diastolic
    • MD ‐1.04 (95% CI, ‐1.86 to ‐0.22)
    • 1915 participants; 8 studies; high‐certainty evidence
• Men
  • Systolic
    • MD ‐2.14 (95% CI, ‐3.71 to ‐0.59)
    • 507 participants; 5 studies; moderate‐certainty evidence
  • Diastolic
    • MD ‐1.99 (95% CI, ‐3.25 to ‐0.74)
    • 507 participants; 5 studies; moderate‐certainty evidence

Effect On Blood Pressure More Pronounced with Higher Calcium Doses

• Low doses (<1000 mg)
  • Systolic
    • MD ‐0.02 (95% CI, ‐2.23 to 2.20)
    • 302 participants; 3 studies; moderate‐certainty evidence
  • Diastolic
    • MD ‐0.41(95% CI, ‐2.07 to 1.25)
    • 201 participants; 2 studies; moderate‐certainty evidence
• Intermediate doses (1000 to 1500 mg)
  • Systolic
    • MD ‐1.05 (95% CI, ‐1.91 to ‐0.19)
    • 2488 participants; 9 studies; high‐certainty evidence
  • Diastolic
    • MD ‐2.03 (95% CI, ‐3.44 to ‐0.62)
    • 1017 participants; 8 studies; high‐certainty evidence
• Higher doses (>1500 mg)
  • Systolic
    • MD ‐2.79 (95% CI, ‐4.71 to -0.86)
    • 350 participants; 7 studies = 8; moderate‐certainty evidence
  • Diastolic
    • MD ‐1.35 (95% CI, ‐2.75 to ‐0.05)
    • 1821 participants; 8 studies; high‐certainty evidence
• None of the studies reported adverse events

CONCLUSION:

• Increasing calcium intake through supplementation or dietary fortification produces small reductions in systolic and diastolic blood pressure in normotensive people
  • This effect is particularly pronounced in younger people and varies with calcium dose

The authors state

The effect was confirmed in multiple prespecified subgroups, including a possible dose-response effect, reinforcing the efficacy of the intervention

The effects can be observed after only 3.5 months of intervention

Although the effect is small, an adequate calcium intake should be an objective to be reached in the general population

Randomised controlled trials (RCT) are needed with high power in the early stages of life

Learn More – Primary Sources:

Calcium supplementation for prevention of primary hypertension

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