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Recommendations Summary

HTN: Magnesium 2015

Click here to see the explanation of recommendation ratings (Strong, Fair, Weak, Consensus, Insufficient Evidence) and labels (Imperative or Conditional). To see more detail on the evidence from which the following recommendations were drawn, use the hyperlinks in the Supporting Evidence Section below.


  • Recommendation(s)

    HTN: Dietary Magnesium

    The registered dietitian nutritionist (RDN) should encourage adults with hypertension (HTN) to consume adequate amounts of dietary magnesium to meet the dietary reference intakes (DRI). While important for health, adequate dietary magnesium may or may not aid in blood pressure (BP) control. Results from two studies suggest that the relationship between magnesium intake from food sources and BP in adults with HTN is unclear. 

    Rating: Weak
    Imperative

    HTN: Magnesium Supplements

    If an adult with HTN is unable to meet the DRI for magnesium through food and diet alone, the RDN may consider recommending magnesium supplementation of up to 350mg per day to aid in BP control. Research indicates that magnesium supplementation of 240mg up to 1, 000mg per day reduced systolic blood pressure (SBP) by 1.0mm Hg to 5.6mm Hg and diastolic blood pressure (DBP) by 1.0mm Hg to 2.8mm Hg in adults with HTN. 

    Rating: Fair
    Conditional

    • Risks/Harms of Implementing This Recommendation

      In healthy people, excess magnesium from food does not pose a health risk. When taking magnesium supplements, individuals should not exceed the tolerable upper intake level (UL) for magnesium (350mg or more). 

      • High doses of supplemental magnesium (particularly the forms of magnesium carbonate, chloride, gluconate and oxide) or medications containing magnesium can result in diarrhea, nausea and abdominal cramping (Office of Dietary Supplements)
      • Caution use of magnesium supplements in excess of 350mg in the following individuals with HTN: 
        • Those with impaired renal function
        • Those with kidney failure  due to increased risk of magnesium toxicity (Office of Dietary Supplements).

    • Conditions of Application

      • The HTN: Magnesium Supplements recommendation applies only to individuals with HTN who are unable to meet the DRI for magnesium with food intake alone
      • The RDN should also consider intake of magnesium from over-the-counter antacids (e.g., Rolaids) and laxatives (e.g., Phillips' Milk of Magnesia) (Office of Dietary Supplements). 

    • Potential Costs Associated with Application

      If an individual is unable to meet the DRI for dietary magnesium, there is an additional cost for magnesium supplements.

    • Recommendation Narrative

      A total of six studies were included in the evidence analysis supporting the recommendations:

      • Two positive quality cross-sectional studies (Kesteloot et al, 2011; Schroder et al, 2002)
      • One positive quality meta-analysis (Dickinson et al, 2006) 
      • One positive quality non-randomized controlled trial (Hatzistavri et al, 2009) 
      • One neutral quality randomized controlled trial (RCT) (Bayir et al, 2009)
      • One neutral quality cross-sectional study (Lancaster et al, 2004).
      Dietary Magnesium 
      • Three studies were included in the evidence analysis: Lancaster et al, 2004; Kesteloot et al, 2011; Schroder et al, 2002
      • Results from these studies suggest that the relationship between magnesium intake from food sources and BP in adults with HTN is unclear
      • The studies showed conflicting results for the relationship between dietary intake of magnesium and BP in hypertensive adults:
        • Kestelroot et al, 2011 showed a significant reduction in DBP, but not SBP
        • Lancaster et al, 2004 showed no significant differences in daily magnesium intake between hypertensives and controls
        • Schroder et al, 2002 showed dietary intakes of magnesium above the RDA (more than 350mg per day for men, more than 280mg per day for women) were not significantly related to HTN. 
      Magnesium Supplements 
      • Three studies were included in the evidence analysis: Bayir et al, 2009; Dickinson et al, 2006; Hatzistavri et al, 2009 
      • In these three studies, which included one meta-analysis (representing 12 randomized controlled trials) of adults with HTN, magnesium supplementation of 240mg up to 1, 000mg per day reduced SBP by 1.0mm Hg to 5.6mm Hg and DBP by 1.0mm Hg to 2.8mm Hg.

    • Recommendation Strength Rationale

      • Conclusion statement for Dietary Magnesium is Grade III
      • Conclusion statement for Magnesium Supplements is Grade II.

    • Minority Opinions

      None.