Effect of short-term vitamin D supplementation on markers of vascular health in South Asian women living in the UK--a randomised controlled trial.
OBJECTIVE
Low vitamin D levels and risk factors for vascular disease are both common in South Asian women. This trial evaluated whether vitamin D supplementation could improve markers of vascular health in South Asian women with low 25-hydroxyvitamin D levels.


METHODS
Parallel-group, double-blind, randomised placebo-controlled trial. Healthy South Asian women with baseline serum 25-hydroxyvitamin D levels of <75 nmol/L were randomised to receive a single dose of 100,000 units oral vitamin D3 or matching placebo. Outcomes were measured at baseline, 4 and 8 weeks. The primary outcome was change in endothelial function measured using brachial artery flow-mediated dilatation. Secondary outcomes included blood pressure, arterial stiffness, microvascular function measured using laser Doppler iontophoresis, insulin resistance, serum lipids, circulating markers of inflammation, thrombosis and adipokines.


RESULTS
50 women were randomised, 25 to each group. Mean age was 41 years; mean baseline 25-hydroxyvitamin D level was 27 nmol/L. 25-Hydroxyvitamin D levels rose in the vitamin D group relative to the placebo group by 4 weeks (16 nmol/L, 95% CI 11 to 21, p < 0.001). There was no improvement in flow-mediated dilatation in the vitamin D group relative to placebo at 4 weeks (0.1%, 95% CI -0.9 to 1.1, p = 0.84) or 8 weeks (0.0%, 95% CI -1.4 to 1.4, p = 0.98). There was no improvement in cholesterol, insulin resistance or markers of inflammation. Both platelet activation inhibitor-1 and tissue plasminogen activator levels fell significantly in the vitamin D group relative to placebo at 8 weeks.


CONCLUSIONS
A single large dose of vitamin D3 did not improve blood pressure or endothelial function in South Asian women with low baseline 25-hydroxyvitamin D levels.


BACKGROUND
ISRCTN75081811.
Ageing and Health, University of Dundee, Ninewells Hospital, Dundee DD1 9SY, UK. Electronic address: m.witham@dundee.ac.uk.
Miles D
MD
Witham
Fiona
F
Adams
Golam
G
Kabir
Gwen
G
Kennedy
Jill J F
JJ
Belch
Faisel
F
Khan
D000328:Adult; D001208:Asia / Q000208:ethnology; D001794:Blood Pressure / Q000187:drug effects; D002784:Cholesterol / Q000097:blood; D019587:Dietary Supplements; D004311:Double-Blind Method; D004730:Endothelium, Vascular / Q000187:drug effects / Q000473:pathology; D005260:Female; D006801:Humans; D007249:Inflammation / Q000473:pathology / Q000517:prevention & control; D007333:Insulin Resistance; D008875:Middle Aged; D017395:Plasminogen Activator Inhibitor 1 / Q000097:blood; D013927:Thrombosis / Q000208:ethnology / Q000473:pathology; D013997:Time Factors; D010959:Tissue Plasminogen Activator / Q000097:blood; D006113:United Kingdom / Q000453:epidemiology; D014652:Vascular Diseases / Q000097:blood / Q000208:ethnology; D059289:Vascular Stiffness; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000627:therapeutic use; D014808:Vitamin D Deficiency / Q000097:blood* / Q000208:ethnology*
D017395:Plasminogen Activator Inhibitor 1; C051321:SERPINE1 protein, human; D014807:Vitamin D; D002784:Cholesterol; C104450:25-hydroxyvitamin D; D010959:Tissue Plasminogen Activator
Arterial stiffness; Endothelial function; Randomised controlled trial; Vitamin D