Cardiovascular disease (CVD) is the leading cause of death in the United States, accounting for one death every 33 seconds. And CVD events such as heart attacks and strokes are only predicted to increase as our population continues to age and chronic diseases become more common.
Observational studies have shown a strong link between vitamin D levels and CVD risk, but previous randomized, placebo-controlled trials haven’t found evidence that vitamin D supplements can prevent cardiovascular events possibly due to poor trial design.
With that in mind, a team of Australian researchers designed a large-scale, long-term study to determine whether vitamin D supplementation could affect the rate of cardiovascular events over the age of 60. Their results—showing that the vitamin did, indeed, reduce risk—were published in The BMJ in June.
The researchers’ D-Health Trial involved 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 5 years.
The researchers then tracked hospital admissions and deaths among the participants to determine the number of major cardiovascular events, including heart attacks, strokes, and coronary revascularization (treatment to restore normal blood flow to the heart).
During the trial, 1,336 participants experienced a major cardiovascular event (6.6% in the placebo group and 6% in the vitamin D group). The overall rate of major cardiovascular events was 9% lower in the vitamin D group compared with the placebo group (the equivalent of 5.8 fewer events per 1,000 participants), with the vitamin D group showing a 19% lower rate of heart attacks and an 11% lower rate of coronary revascularization. The rate of stroke between the two groups, however, was nearly identical.
The researchers also noted that there was some indication that vitamin D produced a stronger preventive effect in volunteers who were using statins or other cardiovascular drugs at the start of the trial, although those results were not statistically significant.
While the absolute risk difference observed in the study was small, it was statistically significant. As this was the largest trial of its kind to date, with extremely high retention and adherence (80% of participants reported taking at least 80% of the study tablets), the researchers say that it shows the promise of vitamin D supplementation and the need for continued research.
“This protective effect could be more marked in those taking statins or other cardiovascular drugs at baseline,” they wrote, suggesting that 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 risk of cardiovascular disease are premature.”