It seems the most studied and tested vitamin these days is vitamin D. Never mind that it is not considered by many to be an actual vitamin—some consider it more of a prohormone, which is an interglandular hormone precursor.
Others consider it a prehormone that can be converted into a hormone. A few refer to it as a hormone, while most consider it a vitamin simply because it’s taken in from outside sources; and a deficiency of the vitamin results in disease. 
As with the process of metabolizing sunshine, UVB rays, or even supplements into the final product, vitamin D seems to go through phases that mimic all those argued labels.
For now, understand that vitamin D from sunshine and/or vitamin D3 supplements is necessary for maintaining sufficient blood levels of D3 to ward off and even reverse most disease.
Study on vitamin D levels and heart health with hypertension
This study was conducted in Turkey by two separate cardiology departments in two cooperating institutions, and published by PubMed June 24, 2013. Two sources for the same study have different reports on how the study was performed.
Source  shows 33 subjects used in the study while source  shows 133. They both agree on other items. The subjects were recently diagnosed with hypertension or high blood pressure. The mean age of all subjects was around 63 within a 10 year time frame.
They were both divided into two groups in order to compare those whose serum 25-Hydroxyvitamin D or 25(OH)D level was above normal, to those below normal. The standard for normal used, 20 ng/ml (nanograms per milliliter) is an outmoded norm even by current the American mainstream medical standard of 30 ng/ml.
After measuring several markers among both high and low serum D level subjects, they determined that vitamin D plays a role in reducing cardiovascular inflammation, arterial and left ventricular heart stiffness among recently diagnosed hypertensive patients.
Bottom line: If your blood pressure is on the high side, plenty of vitamin D through sunshine exposure or supplementation may preserve cardiovascular integrity and help avoid a heart attack.
Read more at Natural News.