Vitamin D Supplements Do Not Appear to Lower Blood Pressure
In March, JAMA Internal Medicine reported that vitamin D supplements do not effectively lower blood pressure, according to a systematic review and meta-analysis. Low vitamin D levels in the blood have previously been associated with elevated blood pressure and cardiovascular events.
The study examined findings from 46 randomized, placebo-controlled trials that involved at least four weeks of vitamin D supplementation. They reported both baseline and follow-up data on blood pressure. Individual patient data was also examined from 27 of the trials (a sum of 3,092 patients).
The researchers searched MEDLINE, CINAHL, EMBASE, the Cochrane Central Register of Controlled Trials, and http://www.ClinicalTrials.com, as well as “hand searched” references from the included articles and previous reviews. They even searched Google for what is known as “gray literature,” material not published in recognized scientific journals. No language restrictions were applied. The search period spanned January 1, 1966, through March 31, 2014.
Individual patient data on age, sex, medication use, diabetes, baseline and follow-up blood pressure, and vitamin D levels were requested from the authors of the included studies. For trial-level data, between-group differences in blood pressure change were combined in a random-effects model. For individual patient data, between-group differences in blood presure at the final follow up, adjusted for baseline blood pressure, were calculated before combining in a random-effects model.
At both the trial level and individual patient level, the data suggested that vitamin D supplementation did not significantly affect systolic or diastolic blood pressure. Findings were similar in subgroup analyses limited to patients with elevated baseline blood pressure or diabetes.
"The lack of effect argues against a role for vitamin D supplementation as a means of BP control in individual patients or as a population-based intervention," the authors conclude.
This comes at a time when calcium supplements are under fire. Vitamin D helps the body absorb calcium, and so the two are often paired together.
In February 2013, the United States Preventive Services Task Force recommended that postmenopausal women refrain from taking supplemental calcium and vitamin D. After reviewing more than 135 studies, the task force said there was little evidence that these supplements prevent fractures in healthy women.
Moreover, several studies have linked calcium supplements to an increased risk of heart attacks and death from cardiovascular disease. Others have found no effect, depending on the population studied and when calcium supplementation was begun.