Scientists say that their recent study, the largest of its kind, suggests a link between vitamin D levels and the risk of cardiovascular disease (CVD), which is one of the main causes of global deaths, and predicted to escalate as populations continue to age and chronic diseases become more common.
Observational studies have consistently shown a link between vitamin D levels and the risk of CVD, reports The Guardian.
However, randomised controlled trials previously found no evidence that supplements prevented CVD events, possibly due to differences in trial design that can affect results.
However, after a randomised controlled trial involving more than 21 000 people over 60, the researchers said the findings suggests vitamin D supplements could reduce the risk of major cardiovascular events.
The study was published in the The BMJ.
The Australian researchers said the absolute risk difference was small, but that this was the largest trial of its kind to date and that further evaluation was now warranted.
“These findings indicate that vitamin D supplementation might reduce the incidence of major cardiovascular events,” they wrote. More trials were needed, but they said it suggested previous thinking that vitamin D supplements do not alter CVD risk was “premature”.
The study, which was led by the QIMR Berghofer medical research institute in Queensland as part of its population health programme, was carried out between 2014 and 2020 and involved 21 315 Australians aged 60 to 84 who randomly received a vitamin D supplement or placebo taken orally at the beginning of each month for up to five years.
During the trial, 1 336 people experienced a major cardiovascular event – 6.6% in the placebo group and 6% in the vitamin D group.
The rate of major cardiovascular events was 9% lower in the vitamin D group compared with the placebo group, equivalent to 5.8 fewer events per 1 000 participants.
The rate of heart attack was 19% lower in the vitamin D group, and there was no difference in stroke risk between the two groups.
Overall, the researchers calculated that 172 people would need to take monthly vitamin D supplements to prevent one major cardiovascular event.
They acknowledged limitations of the trial and said the findings might not apply to other populations. However, this was a large trial with extremely high retention and adherence, and almost complete data on cardiovascular events and mortality outcomes.
Vitamin D helps regulate the amount of calcium and phosphate in the body. These nutrients are needed to keep bones, teeth and muscles healthy.
Study details
Vitamin D supplementation and major cardiovascular events: D-Health randomised controlled trial
Bridie Thompson, Mary Waterhouse, Dallas English, et al.
Published in The BMJ on 28 June 2023
Abstract
Objective
To investigate whether supplementing older adults with monthly doses of vitamin D alters the incidence of major cardiovascular events.
Design
Randomised, double blind, placebo controlled trial of monthly vitamin D (the D-Health Trial). Computer generated permuted block randomisation was used to allocate treatments.
Participants
21 315 participants aged 60-84 years at enrolment. Exclusion criteria were self-reported hypercalcaemia, hyperparathyroidism, kidney stones, osteomalacia, sarcoidosis, taking >500 IU/day supplemental vitamin D, or unable to give consent because of language or cognitive impairment.
Intervention
60 000 IU/month vitamin D3 (n=10 662) or placebo (n=10 653) taken orally for up to five years. 16 882 participants completed the intervention period: placebo 8270 (77.6%); vitamin D 8552 (80.2%).
Main outcome measures
The main outcome for this analysis was the occurrence of a major cardiovascular event, including myocardial infarction, stroke, and coronary revascularisation, determined through linkage with administrative datasets. Each event was analysed separately as secondary outcomes. Flexible parametric survival models were used to estimate hazard ratios and 95% confidence intervals.
Results
A total of 21 302 people were included in the analysis. The median intervention period was five years. 1336 participants experienced a major cardiovascular event (placebo 699 (6.6%); vitamin D 637 (6.0%)). The rate of major cardiovascular events was lower in the vitamin D group than in the placebo group (hazard ratio 0.91, 95% confidence interval 0.81 to 1.01), especially among those who were taking cardiovascular drugs at baseline (0.84, 0.74 to 0.97; P for interaction=0.12), although the P value for interaction was not significant (<0.05). Overall, the difference in standardised cause specific cumulative incidence at five years was −5.8 events per 1000 participants (95% confidence interval −12.2 to 0.5 per 1000 participants), resulting in a number needed to treat to avoid one major cardiovascular event of 172. The rate of myocardial infarction (hazard ratio 0.81, 95% confidence interval 0.67 to 0.98) and coronary revascularisation (0.89, 0.78 to 1.01) was lower in the vitamin D group, but there was no difference in the rate of stroke (0.99, 0.80 to 1.23).
Conclusions
Vitamin D supplementation might reduce the incidence of major cardiovascular events, although the absolute risk difference was small and the confidence interval was consistent with a null finding. These findings could prompt further evaluation of the role of vitamin D supplementation, particularly in people taking drugs for prevention or treatment of cardiovascular disease.
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