14 Aug Vitamin D Supplementation: No Significant Blood Pressure Reduction
MedicalResearch.com: What are the main findings of the study?
Answer: We gave high dose vitamin D3 (100,000 units) or placebo every 3 months to people aged 70 or over, who all had isolated systolic hypertension (ISH). The main focus of the trial was to test whether vitamin D supplementation could reduce blood pressure in this group of patients – this pattern of blood pressure, whether the systolic (top number) is high, and the diastolic (bottom number) is normal, is very common in older people. Previous studies have suggested a link between low vitamin D levels and higher blood pressure, but no trial has yet tested this idea in older patients with ISH.
Despite the treatment causing a significant increase in circulating vitamin D levels, we saw no significant reduction in blood pressure with vitamin D supplementation, despite the trial running for a year. We tested whether certain groups might still benefit – e.g. those with very high blood pressure or very low vitamin D levels, but even these groups did not show a reduction in blood pressure.
We also tested whether vitamin D supplementation reduced the health and stiffness of arteries – both important predictors of future heart attack or stroke. Unfortunately, vitamin D did not affect these measures either, and didn’t reduce cholesterol or glucose levels.
On the more positive side, vitamin D supplements did appear safe, and the number of falls in the vitamin D group was slightly lower than in those people who received placebo. This is reassuring, as an earlier study (Sanders et al) had suggested that very high doses of vitamin D might make falls more likely, in contrast to previous low dose studies that show a protective effect of vitamin D against falls.
MedicalResearch.com: Were any of the findings unexpected?
Answer: Our findings are disappointing, but perhaps not unexpected. Before this study, small trials had suggested that vitamin D supplements might lower blood pressure a little – but no-one had tested the idea in this particular patient group. Vitamin D supplementation might still be useful for other selected groups with high blood pressure – more trials are needed.
MedicalResearch.com: What should clinicians and patients take away from your report?
Answer: At the moment, there is no proven role for using vitamin D to reduce blood pressure in people with high blood pressure. It is still useful to help treat osteoporosis, falls and to treat rickets and osteomalacia, but our results don’t support extending the indications for vitamin D use beyond these core areas.
MedicalResearch.com: What recommendations do you have for future research as a result of this study?
Answer: We are gathering together data from all of the published trials that have tested the effect of vitamin D on blood pressure in a global collaboration (the D-PRESSURE collaboration); this should help us to identify whether there are other groups of patients who might still get a reduction in blood pressure from vitamin D supplements. Once we know this, we will be able to design further trials. In the meantime, large trials of vitamin D supplementation are underway, such as those led by JoAnn Manson from Harvard, and Robert Scragg in New Zealand – vitamin D might still have benefits on heart disease and stroke via alternative biological pathways to blood pressure and cholesterol.
Witham MD, Price RG, Struthers AD, et al. Cholecalciferol Treatment to Reduce Blood Pressure in Older Patients With Isolated Systolic Hypertension: The VitDISH Randomized Controlled Trial. JAMA Intern Med. 2013;():-. doi:10.1001/jamainternmed.2013.9043.