Atrial fibrillation (AF) is the most common type of arrhythmia, or abnormal heart rhythm. The risk of developing AF increases with age, and it’s associated with an increased chance of stroke, heart failure, and death. Previous research has shown that vitamin D deficiency is associated with a higher risk of AF, but there had been no evidence that vitamin D supplementation could help stave off this risk—until now.
Conducted as part of the Finnish Vitamin D Trial (FIND) at the University of Eastern Finland from 2012 to 2018, a study published online in the American Heart Journal in June found that taking higher than recommended doses of vitamin D decreased the risk of atrial fibrillation in older men and women by up to 32 percent.
Designed to test the effectiveness of vitamin D supplementation on the incidence of various cardiovascular diseases and cancers, the FIND study involved 2,495 participants aged 60 and over (for men) or 65 and over (for women). The volunteers were divided into three randomized groups: a placebo group, a group that received a 40-mcg supplement of vitamin D each day, and a group that received an 80-mcg supplement of vitamin D per day. All participants were also allowed to take a personal vitamin D supplement of up to 20 mcg per day, which was the recommended dosage for this age group at the beginning of the study. At baseline, none of the participants had been diagnosed with cardiovascular disease or cancer.
Over the course of the study, the volunteers routinely completed comprehensive questionnaires covering their risk factors for cardiovascular disease and cancer—including lifestyle and nutritional factors—and any occurrence of heart disease or cancer. Data on the occurrence of diseases and deaths was also obtained from Finnish nationwide health registers. Approximately 20 percent of participants were also randomly selected for more detailed examinations and blood samples.
At the end of the five-year study, 190 participants had been diagnosed with atrial fibrillation: 76 in the placebo group, 59 in the 40-mcg group, and 55 in the 80-mcg group. The risk of AF was 27 percent lower in the 40-mcg group, and 32 percent lower in the 80-mcg group when compared to the placebo group. “These post hoc analyses suggest that high-dose vitamin D3 supplementation may reduce incidence of AF in a generally healthy, largely vitamin D-sufficient, elderly population,” the researchers wrote in their conclusion.
According to the authors, FIND is the first randomized controlled trial to observe that vitamin D supplementation reduces the risk of atrial fibrillation in generally healthy men and women. Previous research included only two randomized trials that did not show an effect when using doses of 10 mcg or 50 mcg per day.
“[O]ur findings suggest possible benefit in AF prevention with high-dose vitamin D supplementation in an elderly population, despite relatively high baseline [vitamin D] concentrations. Given the divergent findings from other [randomized controlled trials], additional RCTs, especially in diverse populations are needed to elucidate the role of vitamin D supplementation in AF prevention.” The scientists especially emphasize that more research is needed “before doses of vitamin D that significantly exceed current recommendations can be recommended for preventing atrial fibrillation.”
The FIND study previously published findings showing no association between vitamin D supplementation and the incidence of other cardiovascular events or cancers.