Could Vitamin D Play a Role in Lowering CV Risk?

Vitamin D supplementation may not confer cardiovascular or mortality benefit in the general population, despite previous evidence suggesting an association between low serum vitamin D levels and cardiovascular disease (CVD) risk, according to new findings published in JAMA Cardiology.¹

“Vitamin D supplementation should not be prescribed for the purpose of CVD prevention. This could be surprising to many health care providers because there was a belief that vitamin D could be helpful for this purpose,” lead author Mahmoud Barbarawi, MD, research chief resident at Michigan State University’s Hurley Medical Center, told Nutrition411 via email.

Dr Barbarawi and colleagues arrived at their conclusion after performing a meta-analysis of 21 randomized clinical trials (N = 83,291) published through December 15, 2018. Of these trials, only 4 had prespecified CVD as a primary outcome. A total of 41,669 patients received vitamin D supplementation and 41,622 received placebo.

Major adverse cardiovascular events (MACE) comprised the primary outcome, while rates of myocardial infarction (MI), stroke or cerebrovascular accident, CVD mortality, and all-cause mortality served as secondary endpoints.

Findings suggested that, compared with placebo, vitamin D was not associated with reduced risks of MACE (risk ratio [RR] 1.00), MI (RR 1.00), stroke (RR 1.06), CVD mortality (RR 0.98), or all-cause mortality (RR 0.97). These findings appeared to be consistent based on sex, baseline levels of 25-hydroxyvitamin D, and vitamin D dosage, among other factors.

However, further research may still be warranted, said Dr Barbarawi. “Although our study was powered enough, we still believe that more large trials are needed for subgroups depending on age, sex, ethnicity, and baseline vitamin D level,” he told Nutrition411.

Vitamin D is one of 2 food supplements recently dropped from the list of effective supplements for CVD prevention, along with omega-3 fatty acid supplements, Dr Barbarawi told Nutrition411. In a 2018 meta-analysis also published in JAMA Cardiology, Aung et al found that omega-3 fatty acid supplementation appeared to have no significant association with reduced risk of coronary heart disease or any major vascular events.²

With these findings in mind, other existing, proven methods of CVD prevention should be utilized instead, Dr Barbarawi told Nutrition411.

“There are still many measures that can be taken to prevent CVD, such as aspirin, which showed a significant benefit that should be weighted with the risk of bleeding,” he said. “Other measures of CVD prevention include regular exercise, balanced diet, quitting smoking, and good control of hypertension and diabetes.”

The effects of vitamin D supplementation in type 2 diabetes have made recent headlines as well. Similar findings regarding the impact of vitamin D supplementation on type 2 diabetes risk were published in the New England Journal of Medicine and presented at the American Diabetes Association’s 79th Scientific Sessions.³

In a cohort of patients with high type 2 diabetes risk without vitamin D insufficiency, vitamin D supplementation was not found to be associated with lower odds of diabetes, despite previous studies suggesting a potential association between lower blood 25-hydroxyvitamin D levels and type 2 diabetes risk.³

Amid these recent developments, Ashed A. Quyyumi, MD, and Ibhar Al Mheid, MD, from the Emory University School of Medicine in Georgia, noted in an accompanying editorial to Barbarawi et al’s findings that vitamin D supplementation is still indicated in some patient populations.

“[I]t also should be emphasized that vitamin D therapy in patients with chronic kidney disease and hyperparathyroidism is definitely indicated, and such therapy has established cardiovascular benefits, including blood pressure reduction, reduced electrolyte derangements, and overall reduced cardiovascular mortality rates in patients on hemodialysis,” wrote Drs Quyyumi and Al Mheid.⁴

—Christina Vogt

References:

1. Barbarawi M, Kheiri B, Zayed Y, et al. Vitamin D supplementation and cardiovascular disease risks in more than 83,000 individuals in 21 randomized clinical trials: a meta-analysis [Published online June 19, 2019]. JAMA Cardiol. doi:10.1001/jamacardio.2019.1870.

2. Aung T, Halsey J, Kromhout D, et al. Associations of omega-3 fatty acid supplement use with cardiovascular disease risks: meta-analysis of 10 trials involving 77,917 individuals. JAMA Cardiol.2018;3(3):225-233. doi:10.1001/jamacardio.2017.5205.

3. Pittas AG, Dawson-Hughes B, Sheehan P, et al. Vitamin D supplementation and prevention of type 2 diabetes [Published online June 7, 2019]. N Eng J Med. doi:10.1056/NEJMoa1900906.

4. Quyyumi AA, Al Mheid I. The demise of vitamin D for cardiovascular prevention –Published online June 19, 2019]. JAMA Cardiol. doi:10.1001/jamacardio.2019.1906.