The role of vitamin D in blood pressure and heart health has been the topic of considerable investigation since at least the mid-1980s, the conclusions of the research studies are difficult to interpret. While it is known that both the blood vessels and the heart have large numbers of vitamin D receptors which means that vitamin D is providing some function in regulating these tissues figuring out what these receptors do has been difficult. Studies on the action of vitamin D sometimes appear to contradict each other, and sometimes they yield data that cannot be accurately interpreted.
One study found that administering vitamin D to older adults with existing high blood pressure caused both the systolic blood pressure and diastolic blood pressure to decrease. The same study also found that giving both vitamin D and calcium together caused even larger decreases in both systolic and diastolic blood pressure. These data suggest that vitamin D and calcium somehow work together to cause a reduction in blood pressure and that high levels of calcium promote the blood pressure reducing action of vitamin D. Curiously though, when the study participants were examined more carefully, it was found that this only worked in people who had relatively high calcium levels to start. In people who had low calcium levels at the beginning, neither vitamin D nor vitamin D plus calcium were very effective at lowering blood pressure.
While it is clear that vitamin D plays some role in the regulation of blood pressure, and that people with low levels of vitamin D are more likely to develop cardiovascular problems.
