Vitamin D supplements do not appear to lower blood pressure in older people with common types of hypertension, a British study concludes.

Reuters reports that contrary to previous research, the blood pressure of patients aged 70 or older remained unchanged after a year of heavy vitamin D supplementation.

"It doesn't look like - at the moment - (people) are going to be able to control their blood pressure with vitamin D supplements," said lead author Miles Witham of the University of Dundee in Scotland. "It's important that people who have high blood pressure go on taking their medications."

The new study enrolled 159 people with high isolated systolic blood pressure and low vitamin D levels in a year-long experiment, in which half of the participants received vitamin supplements and the rest placebo pills.

Although the treatment group’s vitamin D levels increased to the value recommended by the Center for Disease Control and Prevention (CDC), their blood pressure remained high, with an average value virtually identical to that recorded prior to the vitamin supplementation.

A disappointing result, Witham said. However, he noted that while the supplement had limited success among hypertension patients selected at random, it may prove effective for certain groups – diabetics, for instance.

"There may be merit in doing other blood pressure trials, but perhaps we have to take a step back to look at what groups we want to lower blood pressure using vitamin D," he said.

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Dr. Edward Giovannicci, Professor of Nutrition and Epidemiology at Harvard University’s School of Health, suggested that the test subjects may have had relatively high levels of vitamin D to begin with.

"Thus, the potential benefit of vitamin D on blood pressure could depend on one's starting point,” he added.

According to the CDC, a third of American adults have high blood pressure. Viewed by physicians as “silent killer,” the condition increases the risk of stroke and heart disease – the leading causes of death in the U.S. To learn more about hypertension and how to prevent it, consult the National Institutes of Health (NIH) guide to lowering blood pressure.

Source: Witham MD, Price RG, Struthers AD, et al. Cholecalciferol Treatment to Reduce Blood Pressure in Older Patients With Isolated Systolic Hypertension: The VitDISH Randomized Controlled Trial. JAMA Intern Med. 2013;():-. doi:10.1001/jamainternmed.2013.9043.