Monthly high-dose vitamin D supplements did not protect people against cardiovascular disease, results from a large, international study have shown.
The randomised controlled trial, carried out by researchers in New Zealand, the UK and the US, found no significant difference in the incidence of cardiovascular disease and death between patients taking a high monthly vitamin D dose and those taking a placebo.
Just over 5,000 patients were assigned to receive either the oral vitamin D supplement – an initial dose of 200,000IU followed by monthly doses of 100,000IU – or a placebo, for an average of around 3.5 years.
There was no significant difference in cardiovascular disease events and deaths during follow-up between the vitamin D and placebo groups, with 11.8% and 11.5% of patients respectively experiencing such an event.
There was also no difference between the groups in the time to the first event.
The team said the results suggested that earlier findings from observational studies of an inverse association between vitamin D levels and cardiovascular disease may simply be explained by other lifestyle risk factors.
However, they also pointed out that their study did not rule out potential benefits of more frequent vitamin D supplementation.
‘The results of this large population-based randomised controlled trial indicate that vitamin D supplementation given in the dose and frequency we used does not prevent cardiovascular disease,’ they said.
‘The effects of daily or weekly dosing on CVD risk require further study.’