Vitamin D is a vitamin which has been vastly underestimated. For several years vitamin D has always been associated with bone formation simply because of the ability of vitamin D to promote the absorption of calcium from the intestine. Recently, vitamin D has been assigned other roles which are so important that vitamin D deficiency could lead to coronary heart disease, diabetes, hypertension and cancer. Vitamin D is known to activate several genes.
Vitamin D and Blood Pressure
Statistical evidence suggests that people living near the equator are less likely to have hypertension while as we move away from the equator, the incidence of hypertension increases. Also during the winter period, when the availability of sunlight is low, there are surges in the blood pressure. Exposure to sunlight is a major contributor to vitamin D generation in the body. There have also been reports that vitamin D supplementation can lead to a drop in the systolic and diastolic blood pressures. Moderate exposure to UV light which increases endogenous vitamin D synthesis also causes a drop in the blood pressures in individuals suffering from hypertension.
Role of Angiotensin II
Thus, it is clear that vitamin D has a role in regulating the blood pressure. How does vitamin D bring about a fall in the blood pressure? To understand this, one must get acquainted with the factors involved in the phenomenon of blood pressure homeostasis. Blood pressure is elevated because of a substance called angiotensin II.
Renin, the enzyme, is released from the kidneys.
Angiotensinogen, the protein, is released from the liver.
Angiotensin converting enzyme (ACE) is present in the lungs.
Aldosterone, the hormone, is released from the adrenal glands.
Whenever blood pressure falls, an enzyme called renin is released into the circulation from the juxtaglomerular apparatus of the kidneys. The substance on which this enzyme acts is a protein called angiotensinogen. This protein has no activity. Renin acts on angiotensinogen to produce a peptide called angiotensin I. This peptide is split further into another peptide angiotensin II while the blood is passing through the lungs. This conversion of angiotensin I into angiotensin II is brought about by the enzyme called angiotensin converting enzyme (ACE). This peptide angiotensin II is the substance responsible for elevating the blood pressure. Angiotensin II is able to constrict the blood vessels, a process which elevates the blood pressure. When excess of angiotensin II is produced hypertension results.
ACE Inhibitors
In addition, angiotensin II also stimulates the release of the hormone aldosterone from the adrenal glands. This hormone promotes the reabsorption of sodium from the tubules of the kidneys. This reabsorption of sodium also increases the blood pressure. This is also precisely why people suffering from hypertension are advised to reduce their salt consumption. The traditional method of treating hypertension has been to inhibit the enzyme ACE. This prevents the formation of angiotensin II.
How Does Vitamin D Act?
While there is no doubt that the use of ACE inhibitors has benefited hypertensive individuals, this method of treatment has produced many side effects. The entire cascade of reactions leading to the formation of angiotensin II starts with the release of the enzyme rennin. This is the site of action of vitamin D. Vitamin D suppresses the release of renin by silencing the gene responsible for the formation of renin. Thus, vitamin D deficiency could be one of the factors responsible for the onset of hypertension and the condition could be reversed by the supplementation of vitamin D which also helps to prevent the onset of many other diseases. One should remember that vitamin D is free and all that you have to do is to be out there getting exposed to sunlight.
Sources
- Yan Chun Li, Vitamin D regulation of the renin-angiotensin system. Journal of Cellular Biochemistry. 2003, 1: 88(2):327-331
- Anand vaidya et al, 25-Hydroxy vitamin D is associated with plasma renin activity and the pressor response to dietary sodium intake in Caucasians. Journal of Renin-Angiotensin-Aldosterone System. 2011, 12: 311-319
Disclaimer
The information contained in this article is for educational purposes only and should not be used for diagnosis, or to guide treatment without the opinion of a health professional. Any reader who is concerned about his or, her health should contact a doctor for advice.
Vangeepuram Satakopan - I am using my 32 years' experience in the field of BIochemistry to explain health related topics. Dr.Vangeepuram Satakopan
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