Hypertension (high blood pressure) is systolic blood pressure greater than 140 mm of mercury (Hg) and diastolic blood pressure greater than 80 mm Hg.
Hypertension is an important risk factor for chronic kidney disease1 and cardiovascular disease incidence and death2. Risk of hypertension increases with age, African-American race, obesity, excess stress, smoking, diabetes, diets high in sodium [http://www.nlm.nih.gov/medlineplus/ency/article/000468.htm] and diets high in added sugar3.
Blood pressure and hypertension are higher at higher latitudes and in winter, but both solar ultraviolet (UV) irradiance and temperature can affect blood pressure, so it is not clear that vitamin D explains these variations.
One way UV irradiance lowers blood pressure is through liberation of nitric oxide from nitrogen compounds under the skin.
Serum 25-hydroxyvitamin D [25(OH)D] levels have been found inversely correlated with blood pressure and prevalence of hypertension in observational studies. However, vitamin D supplementation studies have had limited success in lowering blood pressure.
Those with hypertension seem most likely to benefit.
There are several mechanisms whereby vitamin D can lower blood pressure including effects on the renin angiotensin aldosterone system. Renin is a proteolytic enzyme secreted by the kidneys, which catalyzes the production of angiotensin, which, in turn, mediates extracellular fluid volume (blood plasma, lymph and interstitial fluid) and arterial vasoconstriction.
Further work is required to fully understand the role of UV irradiance and vitamin D in affecting blood pressure.
Normal blood pressure is below 120 mm of mercury (Hg) for systolic blood pressure and below 80 mm Hg while hypertension is defined as systolic blood pressure greater than 140 mm Hg and diastolic blood pressure greater than 90 mm Hg4.
Page last edited: 09 May 2011
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