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Recommendations Summary

HTN: Vitamin D 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: Vitamin D

    The registered dietitian nutritionist (RDN) should encourage adults with hypertension (HTN) to consume adequate amounts of vitamin D to meet the dietary reference intakes (DRI). While important for health, vitamin D may or may not aid in blood pressure (BP) control. Data from observational and intervention studies are inconclusive regarding the association between vitamin D status or intake (from supplements or food sources) and BP in individuals with HTN.  

    Rating: Weak
    Imperative

    • Risks/Harms of Implementing This Recommendation

      There are no potential risks or harms associated with the application of this recommendation.

    • Conditions of Application

      There are no conditions that may limit the application of this recommendation.

    • Potential Costs Associated with Application

      There are no obvious costs associated with the application of this recommendation.

    • Recommendation Narrative

      Eight studies (seven citations) were included in the evidence analysis supporting this recommendation: 

      • Two positive quality cross-sectional studies (Fiscella et al, 2011; Mateus-Hamdan et al, 2013)
      • Three neutral quality randomized controlled trials (RCTs) (Larsen et al, 2012; Wamberg et al, 2013; Witham et al, 2013)
      • One neutral quality non-randomized controlled trial (Bernini et al, 2013)
      • One neutral quality non-controlled trial (Bernini et al, 2013)
      • One neutral quality retrospective cohort study (Vacek et al, 2012).
      Eight observational and intervention studies provide inconclusive evidence regarding the association between vitamin D status or intake and blood pressure (BP) in individuals with hypertension (HTN). 
      • Effect of vitamin D deficiency and change in BP:
        • Fiscella et al, 2011 showed that participants in the lowest quintile of serum vitamin D (2ng to 15ng per ml) had mean SBP levels of 2.64mm Hg (2.58mm Hg to 2.70mm Hg) higher than those in the highest quintile (31ng to 80ng per ml). In individuals with HTN (24% of the sample), those in the lowest quintile had a statistically significant 6mm Hg higher SBP than those in the highest quintile (significance level not reported)
        • Vacek et al,  2012 found a significantly higher percentage of individuals with HTN who were vitamin D deficient at baseline. Additionally, vitamin D deficiency was associated with HTN. Bernini et al, 2013 also observed significant differences in plasma vitamin D levels at baseline between hypertensives and normotensives 
        • In contrast, Mateus-Hamdan et al, 2013,  did not observe a difference in serum Vitamin D levels between normotensives and hypertensives. After adjustment for covariables, there was no association between serum vitamin D and SBP or DBP. Additionally, serum vitamin D was not associated with HTN in univariate and multi-variate analyses.
      • Effect of vitamin D supplementation on serum or plasma levels and change in BP:
        • Four of five intervention trials observed significant increases in serum or plasma vitamin D [25(OH)D] levels (Bernini et al, 2013; Larsen et al, 2012; Wamberg et al, 2013; Witham et al, 2013). Amounts and frequency of vitamin D supplementation varied by study. Treatment dose did not appear to influence change in vitamin D levels.
        • In all four of five intervention trials, there were non-significant changes in SBP or DBP 
        • Bernini et al, 2013 found no change in plasma vitamin D levels 
        • In one study (Larsen et al, 2012), there were significant changes in SBP and DBP, in individuals with baseline vitamin D levels less than 32ng per ml.

    • Recommendation Strength Rationale

      Conclusion statement is Grade III.

    • Minority Opinions

      None.