29 June 2023
A major QIMR Berghofer clinical trial, the D-Health Trial, has found vitamin D supplements may reduce the risk of cardiovascular events such as heart attacks in people aged over 60.
The researchers emphasised that the findings are not conclusive, but that they warrant further investigation, particularly for patients who take heart disease medications such as those used to treat high blood pressure or high cholesterol.
The results of the study have been published in the prestigious journal The BMJ.
Lead author and epidemiologist Professor Rachel Neale, who heads QIMR Berghofer’s Cancer Aetiology & Prevention Group, said the trial was the second-largest of its kind to date to investigate whether vitamin D could reduce the risk of cardiovascular events.
“While previous randomised controlled trials have not found that taking supplements is beneficial for this outcome, the findings of the D-Health Trial suggests it is premature to say vitamin D supplementation does not alter the risk,” Professor Neale said.
“Our trial found vitamin D supplementation may reduce the risk of major cardiovascular events, and the protective effect could be more marked in those taking statins and other heart disease drugs. It does suggest that further research into this is needed.”
The QIMR Berghofer D-Health Trial was held from 2014 to 2020 and involved more than 21,000 Australians aged between 60 and 84 who randomly received either vitamin D or a placebo which was taken monthly for up to five years. The aim was to establish the role vitamin D might play in preventing different diseases.
Cardiovascular disease, which leads to events such as heart attacks and strokes, is the leading cause of death globally and is set to increase as populations continue to age and chronic diseases become more common.
During the D-Health Trial, 6 percent of the group assigned to take vitamin D experienced a major cardiovascular event, which was slightly lower than the placebo group at 6.6 percent. The rate of major cardiovascular events was 9 percent lower in the vitamin D group, and the rate of heart attack was 19 percent lower compared to the placebo group.
There was some indication of a stronger effect of the vitamin D in participants who were using statins or other cardiovascular drugs at the start of the trial.
“We’re not sure why this is the case. It could be an indicator of a higher risk at the start of the trial so there was more scope for improvement.
“We do want to stress that these results are not statistically significant, but it was definitely interesting to see that we saw some evidence of benefit in the D-Health participants, even though most of them were not vitamin D deficient,” Professor Neale said.
The research team emphasised that all supplements come at a cost. While there is some evidence that taking vitamin D might reduce the risk of cardiovascular events, this is not conclusive. Consumers therefore need to make their own informed decision about whether to take vitamin D supplements. The team also recommend that anyone considering supplementation who is aged over 60 and has existing conditions should discuss this with their doctor.
The D-Health Trial was the second largest trial ever of vitamin D using a relatively high dose of vitamin D (60,000 IU (international units) per month). After 5 years approximately 80 percent of participants were still taking their tablets, and linkage to national datasets was used to ensure that data on cardiovascular events was essentially complete.
The investigator team would like to acknowledge the contribution of the more than 21,000 Australians who participated in the D-Health Trial.