Vitamin D supplementation does not reduce blood pressure in patients with prehypertension and low vitamin D status, according to the randomized double-blind Vitamin D Therapy in Individuals at High Risk of Hypertension Trial (DAYLIGHT).

Researchers randomized 534 subjects with prehypertension or stage I hypertension and 25 hydroxyvitamin D (25OHD) levels of 25 ng/mL or less to receive either high dose (4,000 IU/d) or low dose (400 IU/d) oral vitamin D₃ for 6 months. At the end of the study, researchers found:

• no significant difference in 24-hour systolic blood pressure (-0.8 mmHg in the high-dose versus -1.6 mmHg in low-dose arms)

• no significant difference in 24-hour diastolic blood pressure (-1.2 in the high-dose and -1.0 in the low-dose arms)

• no association between change in 25OHD levels and reduced 24-hour systolic or diastolic blood pressure

Based on these findings, the authors suggest that the association between vitamin D status and reduced blood pressure does not appear causal.

Citation: Arora P, Song Y, Dusek J, et al. Vitamin D therapy in individuals with prehypertension or hypertension: the DAYLIGHT trial. Circulation. 2015;131(3):254-262. doi: 10.1161/CIRCULATIONAHA.114.011732.

Commentary: Low levels of Vitamin D have been linked to everything from chronic pain to asthma to high blood pressure. With the exception of falls in the elderly and effects on bone mineral density,¹ most of these claims have not held up to more rigorous scientific scrutiny. For instance, an article last year in JAMA showed, in a double-blind randomized trial, that vitamin D supplementation was not effective in improving asthma outcome in individuals with symptomatic asthma and low-vitamin D levels.² This article nicely refutes any relation between treatment of low vitamin D levels and improvement in blood pressure. It appears that the vitamin D train is slowly leaving the station. –Neil Skolnik, MD

1. American Geriatrics Society Workgroup on Vitamin D Supplementation for Older Adults. Recommendations abstracted from the American Geriatrics Society Consensus Statement on Vitamin D for prevention of falls and their consequences. J Am Geriatr Soc 2014 Jan;62(1):147–152.

2. Castro M. Effect of vitamin D3 on asthma treatment failures in adults with symptomatic asthma and lower vitamin D levels. The VIDA Randomized Clinical Trial. JAMA. 2014;311(20):2083-2091. doi:10.1001/jama.2014.5052.