DOES VITAMIN D BENEFIT ONLY THOSE WHO ARE DEFICIENT?

Vitamin   D   is   an   essential   nutrient   obtained   from   sunlight, dietary intake, and supplementation.  Obser­vational   epidemiological   studies   have   consistently   found that low concentrations of circulating 25­hydro x y­      vitamin  D  (25[OH]D),  a  metabolite  used  as  a  clinical  indicator  of  vitamin  D  status,  are  associated  with  an  increased  risk  of  cardiovascular  disease  and  all­cause  mortality,  as  well  as  other  chronic  diseases.

The randomised trials of vitamin D supplementation for cardiovascular disease and all-cause mortality have generally reported null findings.  However,  generalisability  of  results  to  individuals  with  low  vitamin  D  status  is  unclear.   The study is to  characterize   dose-response   relationships   between   25-hydroxy vitamin   D   (25[OH]D)   concentrations  and  risk  of  coronary  heart  disease,  stroke,  and  all-cause  mortality  in  observational  and  Mendelian  randomisation frameworks.

  • There is a significant inverse relationship between concentrations of circulating 25­-hydroxy­-vitamin D (25[OH]D) and all-cause mortality, but only in people with vitamin D35 studies showed that, overall, there is no significant relationship between 25(OH)D concentrations, a clinical indicator of vitamin D status, and the incidence of coronary heart disease (CHD), stroke, or all-cause death.
  • In vitamin D deficient individuals, each 10 nmol/L increase in 25(OH)D concentrations reduced the risk of all-cause mortality by 31%.(Stephen Burgess, PhD)
  • There was a non-significant link between 25(OH)D concentrations and stroke and CHD, but again, only in vitamin D deficient individuals. (Research, published in The Lancet Diabetes & Endocrinology)
  • The result of the study an accompanying editorial, Guillaume Butler-LaPorte, MD, and J. Brent Richards, MD, “could have important public health and clinical consequences” and will “allow clinicians to better weigh the potential benefits of supplementation against its risk,” such as financial cost, “for better patient care — particularly among those with frank vitamin D deficiency.”
  • “Given that vitamin D deficiency is relatively common and vitamin D supplementation is safe, the rationale exists to test the effect of vitamin D supplementation in those with deficiency in large-scale randomized controlled trials.”
  • The team gathered data from the UK Biobank, the European Prospective Investigation Into Cancer and Nutrition Cardiovascular Disease (EPIC-­CVD) study, 31 studies from the Vitamin D Studies Collaboration (VitDSC), and two Copenhagen population­-based studies.
  • They first performed an observational study that included 384,721 individuals from the UK Biobank and 26,336 from EPIC-­CVD who had a valid 25(OH)D measurement and no previously known cardio­vascular disease at baseline.
  • Researchers also included 67,992 participants from the VitDSC studies who did not have previously known cardiovascular disease. They analyzed 25(OH)D concentrations, conventional cardiovascular risk factors, and major incident cardiovascular morbidity and mortality using individual participant data.
  • The results showed that, at low 25(OH)D concentrations, there was an inverse association between 25(OH)D and incident CHD, stroke, and all-cause mortality.

Up to 7% of Study Participants Were Vitamin D Deficient

  • The 25(OH)D analysis indicated that 3.9% of UK Biobank and 3.7% of Copenhagen study participants were deficient, compared with 6.9% in EPIC-CVD.
  • Across the full range of 25(OH)D concentrations, there was no significant association between genetically­ predicted 25(OH)D levels and CHD, stroke, or all­-cause mortality.
  • The genetic variants may affect 25(OH)D concentrations in a different way from “dietary supplementation or other clinical interventions.”