Taking vitamin D supplements over the age of 60 could help to reduce the risk of cardiovascular disease, an Australian clinical trial has suggested today.
Writing in today’s edition of The BMJ, the researchers, including teams from QIMR Berghofer Medical Research Institute, University of Melbourne, The University of Sydney, and Monash University, say while the absolute risk difference was small, further evaluation is warranted because this was the largest trial of its kind.
Observational studies have consistently shown a link between vitamin D levels and risk of cardiovascular disease, but randomised controlled trials have found no evidence that vitamin D supplements prevent cardiovascular events.
In this D-Health trial, the researchers recruited 21,315 Australians aged 60-84 and monitored them from 2014 to 2020.
Participants were randomly received one capsule of either 60,000 IU vitamin D (10,662 participants) or placebo (10,653 participants) taken orally at the beginning of each month for up to 5 years.
Anyone with a history of high hypercalcemia, hyperparathyroidism, kidney stones, osteomalacia, sarcoidosis, an inflammatory disease, or those already taking more than 500 IU/day vitamin D were excluded.
The teams monitored data on hospital admissions and deaths to identify major cardiovascular events, including heart attacks, strokes and coronary revascularisation.
The average treatment duration was five years and more than 80% of participants reported taking at least 80% of the study tablets.
During the trial, 1,336 participants – 6.6% in the placebo group and 6% in the vitamin D group – experienced a major cardiovascular event, with the rate of major cardiovascular events being 9% lower in the vitamin D compared with the placebo group.
In the vitamin D group, the rate of heart attack was 19% lower, while the rate of coronary revascularisation was 11% lower, but there was no difference in the rate of stroke between the two groups.
There was some indication of a stronger effect in those who were using statins or other cardiovascular drugs at the start of the trial, but the researchers say these results were not statistically significant.
The team calculates that 172 people would need to take monthly vitamin D supplements to prevent one major cardiovascular event.
They say their findings suggest that vitamin D supplementation may reduce the risk of major cardiovascular events.
They write: “This protective effect could be more marked in those taking statins or other cardiovascular drugs at baseline. In the meantime, these findings suggest that conclusions that vitamin D supplementation does not alter risk of cardiovascular disease are premature.”
Thompson B, Waterhouse M, English DR et al. Vitamin D supplementation and major cardiovascular events: D-Health randomised controlled trial BMJ 29 June 2023; doi: 10.1136/bmj-2023-075230
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