Although vitamin D normalization has been credited with many health benefits, there has not yet been a clinical trial looking at the effect of vitamin D supplementation on isolated systolic hypertension. Just such a study was reported recently. Of particular interest is that isolated systolic hypertension (systolic BP >140 and diastolic <90) is the most common form of hypertension and just as serious in terms of adverse outcome, compared to elevations in both systolic and diastolic, when the BP is consistently over 140/90.
In the study reported, randomized participants were deficient to start with (25-hydroxy vitamin D levels less than 30 ng/mL) and sufficiently supplemented to raise levels from an average of 18 to 26, still not normal. There was no significant change in blood pressure, cholesterol, endothelial function, glucose or walking distance.
In general it’s not useful to supplement vitamins in an isolated fashion. If one wanted to try a single supplement for hypertension and see a result over several months, ubiquinol (CoQ10) would be a better choice. On the other hand, a D supplement might be more useful in conjunction with vitamins A and K2, the other fat soluble vitamins that work as co-factors in bone health. (See my discussion of Hypertension for more information.)
Previous reports of normal blood pressure associated with a higher vitamin D level might have shown a benefit if people were keeping normal vitamin D levels by obtaining D in its natural forms: from sunlight and cod liver oil!