QUEENSLAND, Australia — Vitamin D is probably most synonymous with the Sun and strong bone health, but new research out of Australia suggests a regular regimen of vitamin D supplementation can also go a long way toward promoting robust heart health. The study, based on a clinical trial, finds that vitamin D supplements may reduce the risk of major cardiovascular events such as heart attacks among older adults (ages 60+).
Study authors stress that the absolute risk difference was small, but at the same time, this was the largest trial of its kind to date. Further evaluations are no doubt necessary, especially among those taking statins or other cardiovascular disease drugs.
Cardiovascular disease (CVD) is a general term encompassing all conditions affecting the heart or blood vessels and is one of the main causes of death globally. CVD events like heart attacks and strokes are projected to increase as populations continue to live longer and chronic diseases become more and more common.
Prior observational studies have consistently noted a link connecting vitamin D levels and CVD risk, but thus far randomized controlled trials have yielded no evidence that vitamin D supplements prevent cardiovascular events — possibly because of the differences in trial design that can influence results.
To address this, the research team in Australia assessed if supplementing older adults with monthly doses of vitamin D would alter the rate of major cardiovascular events. This D-Health Trial was carried out between 2014 and 2020 and included 21,315 Australians (ages 60-84). Participants received one capsule of either 60,000 IU vitamin D (10,662 people) or a placebo (10,653 people) to take orally at the beginning of each month for up to five years.
Those with a history of high calcium levels (hypercalcemia), overactive thyroid (hyperparathyroidism), kidney stones, soft bones (osteomalacia), sarcoidosis, an inflammatory disease, or anyone already taking more than 500 IU/day vitamin D were excluded from the experiment.
Next, the research team made use of data covering hospital admissions and deaths to identify major cardiovascular events like heart attacks, strokes, and coronary revascularization (a treatment to restore normal blood flow to the heart).
Average treatment duration lasted five years, with over 80 percent reporting taking at least 80 percent of their tablets. Over the course of the trial, 1,336 participants experienced a major cardiovascular event (6.6% in the placebo group, 6% in the vitamin D group). Meanwhile, rate of major cardiovascular events was nine percent lower in the vitamin D cohort compared to the placebo group (equivalent to 5.8 fewer events per 1,000 people).
Heart attack (-19%) and coronary revascularization (-11%) rates were lower in the vitamin D group, but the team did not note any differences in the rate of stroke between the two cohorts. Notably, there was some indication of a stronger effect on those using statins or other cardiovascular drugs at the beginning of the trial. However, researchers clarify those findings were not statistically significant.
All in all, it is estimated that 172 people would need to take monthly vitamin D supplements to stop one major cardiovascular event from occurring.
In conclusion, study authors acknowledge a small underestimation of events may have occurred, and these findings may not apply to other populations, especially populations in which a higher proportion of people are vitamin D deficient. However, this project was still a very large trial with extremely high retention and adherence, as well as a near-complete dataset covering cardiovascular events and mortality outcomes. Researchers believe their findings suggest 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,” researchers add in a media release, suggesting further evaluation is warranted to help to clarify this issue.
“In the meantime, these findings suggest that conclusions that vitamin D supplementation does not alter risk of cardiovascular disease are premature,” the study authors conclude.
The study is published in The BMJ.