New Studies Point to Vitamin D for Lower Blood Pressure, but Research Still Limited

New evidence shows that higher vitamin D levels may assist with lowering blood pressure. The Vitamin D Council, a nonprofit group, has updated its health summary with studies from 2013 and 2014 looking at the link between vitamin D and blood pressure. Current research on vitamin D for hypertension is somewhat limited, making these studies a welcome addition.

In a meta-analysis published in the European Journal of Epidemiology¹ last year, researchers found a dose-dependent link between vitamin D levels and hypertension: each 10-ng/ml increase in vitamin D led to a 12% lower risk of hypertension. Specifically, the researchers looked at baseline levels of circulating 25-hydroxyvitamin D. In short, researchers found that those with the highest levels of vitamin D had a 30% lower risk of developing hypertension compared to those with the lowest vitamin D levels. The meta-analysis encompassed 283,537 patients and 55,816 incidents of hypertension.

Considering that there is a significantly higher rate of high blood pressure in the black versus the white population, and that blacks tend to have lower circulating levels of 25-hydroxyvitamin D, a 2013 study published in Hypertension² looked at whether vitamin D3 can help this segment of the population. Researchers conducted the study over three months during two winters (a period of lower access to sunlight) and evaluated, in randomized, double-blind fashion, four study arms comprising 250 subjects with normal hypertension: placebo, 1000 IU/cholecalciferol (vitamin D3) daily, 2000 IU D3 daily, or 4000 IU D3 daily. They evaluated subjects’ blood pressure and 25-hydroxyvitamin D status at baseline, 3 months, and 6 months and likewise found a dose-dependent relationship between vitamin D status and hypertension. For each 1-ng/ml increase in plasma 25-hydroxyvitamin D, subjects saw a significant 0.2-mm Hg reduction in systolic blood pressure. Researchers concluded that three months of oral vitamin D3 supplementation “significantly, yet modestly, lowered systolic blood pressure” in blacks-although they noted that some subjects may have been taking blood pressure medication.

Finally, a small, 15-subject study published in 2014 in the Journal of the Renin-angiotensin-aldosterone System (JRAAS)³ looked at whether vitamin D3 may help to reduce the activity of the renin-angiotensin system (RAS). The RAS helps regulate blood pressure, and an overactive RAS can increase blood pressure. Subjects took a high, 25,000-IU dose of vitamin D3 once per week for two months. Researchers found that vitamin D3 supplementation helped “blunt systemic RAS activity” and reduce hypertension.

As for the mechanism of action by which vitamin D may lower blood pressure, the Vitamin D Council notes that research hints that not only might vitamin D regulate the RAS; vitamin D may bind to receptors of cells that lead to arterial plaque, helping to reduce a buildup of these cells. But, it notes, “researchers still aren’t sure what causes the blood pressure system to become overactive and don’t know yet for sure how vitamin D can help to control its activity.”

The council does caution that research on vitamin D and hypertension is still very much emerging. More is needed, the group says, because many studies have used a small sample size, and results have been inconsistent. The authors of the European Journal of Epidemiology meta-analysis agree: “The evidence on the association between baseline vitamin D status and risk of incident hypertension in general populations is limited and has not been reliably quantified,” they wrote.

Still, the Vitamin D Council concludes, “If you have hypertension or you are trying to prevent hypertension and want to take vitamin D, it is unlikely to make your hypertension worse or cause you any harm, as long as you take less than 10,000 IU per day. However, we also can’t say for sure if it will help to prevent or treat hypertension.”

Jennifer Grebow
Editor-in-Chief
Nutritional Outlook magazine
jennifer.grebow@ubm.com

References

1. Kunutsor SK et al., “Vitamin D and risk of future hypertension: meta-analysis of 283,537 participants,” European Journal of Epidemiology, vol. 28, no. 3 (March 2013): 205-221.
2. Forman JP et al., “Effect of vitamin D supplementation on blood pressure in blacks,” Hypertension, vol. 61, no. 4 (April 2013): 779-785.
3. Carrara D et al., “Cholecalciferol administration blunts the systemic renin-angiotensin system in essential hypertensives with hypovitaminosis D,”Journal of the Renin-angiotensin-aldosterone System (JRAAS),vol. 15, no. 1 (March 2014): 82-87.