In a randomized controlled clinical trial, people over 60 taking vitamin D had fewer cardiovascular events than those given a placebo. However, the risk differences were slight between the two groups.
Though some studies link vitamin D deficiency to an increased risk of heart disease and stroke, previous 2019 research examining 21 randomized clinical trials found no association between vitamin D supplementation and a reduced risk of cardiovascular disease.
Still, observational studies suggest that the sunshine vitamin may benefit the cardiovascular system.
These conflicting findings leave many unanswered questions about whether vitamin D intake is important for reducing the risk of heart attack, stroke, and other cardiovascular events.
To investigate further, Australian researchers conducted a randomized, double-blind, placebo-controlled trial to determine if vitamin D supplementation changed the incidence of cardiovascular events in older adults.
Their research was published on June 28 in theBMJ.
The team recruited 21,302 adults 60 years old or older between 2014 and 2015. The scientists excluded people with self-reported high calcium levels, soft bones, overactive thyroid, kidney stones, or sarcoidosis from the study. They also did not include those who already took more than 500 IU of vitamin D daily.
Then, the scientists randomly assigned the participants to one of two groups. The first group took one 60,000 IU vitamin D capsule per month, and the other group took a placebo once a month for up to five years.
Using data from the participants' hospital admissions and death records, the team identified the incidence of major cardiovascular events, including heart attack and stroke.
During the study, 699 participants taking the placebo and 637 taking vitamin D experienced a significant cardiovascular event. The analysis showed that the rate of major cardiovascular events was 9% lower in the vitamin D group than in the placebo group.
In addition, the rate of cardiovascular revascularization was 11% lower, and the rate of heart attack was 19% lower in participants who took vitamin D.
Still, the scientists found no differences in stroke rates between those taking vitamin D and placebo participants.
They did, however, find some evidence that vitamin D intake had a more profound effect on participants who were taking statins or other heart-related medications at the study's onset. But statistically, the findings were not significant.
Overall, the analysis found that 172 people would need to take monthly vitamin D supplements to avoid one significant cardiovascular event. However, the team suggests that future research should examine vitamin D's effects on people taking statins or other heart disease drugs, as they did find some indication that vitamin D supplementation had a stronger impact in participants prescribed these medications.
"Vitamin D supplementation might reduce the risk of major cardiovascular events, although the absolute risk difference was small and the confidence interval was consistent with a null finding," the study authors wrote.
Nonetheless, the authors conclude, "These findings suggest that conclusions that vitamin D supplementation does not alter risk of cardiovascular disease are premature."