While the risk difference is said to be small, a clinical trial – the D-Health Trial – published in The BMJ reveals that vitamin D supplements may help prevent cardiovascular events such as heart attacks among those over 60 years of age.
This is the largest trial of its kind and warrants further evaluation, especially in people taking statins or other CVD medications.
As part of the clinical trial, researchers set out to investigate whether supplementing older adults with monthly doses of vitamin D alters the rate of major cardiovascular events.
The trial was carried out from 2014-2020 and included 21,315 Australians aged 60-84 who randomly received one capsule of either 60,000 IU vitamin D (10,662 participants) or a placebo (10,653 participants) taken orally at the beginning of each month for up to 5 years.
Participants with a history of high calcium levels (hypercalcemia), overactive thyroid (hyperparathyroidism), kidney stones, soft bones (osteomalacia), sarcoidosis (an inflammatory disease) or those already taking more than 500 IU/day vitamin D were excluded from the trial.
Data on hospital admissions and deaths were used to identify major cardiovascular events, including heart attacks, strokes, and coronary revascularisation (treatment to restore normal blood flow to the heart).
The average treatment duration was 5 years and more than 80% of participants reported taking at least 80% of the study tablets.
During the trial, 1336 participants 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 compared with the placebo group (equivalent to 5.8 fewer events per 1000 participants).
The rate of heart attack was 19% lower and the rate of coronary revascularisation was 11% lower in the vitamin D group, 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 researchers acknowledge that there may be a small underestimate of events and say the findings may not apply to other populations, particularly those where a higher proportion of people are vitamin D deficient.
However, this was a large trial with extremely high retention and adherence, and almost complete data on cardiovascular events and mortality outcomes.
As such, they say their findings suggest that vitamin D supplementation may reduce the risk of major cardiovascular events.
“This protective effect could be more marked in those taking statins or other cardiovascular drugs at baseline,” they add, and they suggest further evaluation is needed to help to clarify this issue.
“In the meantime, these findings suggest that conclusions that vitamin D supplementation does not alter the risk of cardiovascular disease are premature,” say the researchers.
