Recently there had been a lot of news about Vitamin D (VD), whether it is network news, medical magazine or Readers’ Digest, they are all talking about VD and its deficiency. The importance of VD can be realised when it is linked with cardiovascular problems as well as blood pressure, bone disease and prevention of many cancers.
VD is found in many dietary sources such as fish, eggs, fortified milk, etc. The sun also contributes significantly to the daily production of VD and, as little as 10 minutes of exposure to the arms, legs, face and hands is thought to be enough to prevent deficiencies. There are several forms of VD: Vitamin D2 is synthesised by plants and Vitamin D3 is synthesised by humans in the skin when exposed to sunlight. Sun screen and dark skin pigmentation also reduces skin synthesis of VD.
The major biologic function of VD is to maintain normal blood levels of calcium and phosphorous. VD aids in the absorption of calcium, helping to form and maintain strong bones. Recently, research also suggests VD may provide protection from osteoporosis, hypertension, cancer and several autoimmune diseases. Patients with chronic kidney disease are especially susceptible due to the inability to convert VD to active form leading to VD Deficiency.
Low levels of VD levels might contribute to heart problems. Although VD has been shown to help regulate the body’s disease fighting immune system, researchers have also linked it with high blood pressure, diabetes and obesity. All of which can contribute to heart problems. According to Dr. Edward Giovannucci of the Harvard University, a study of 18,225 men provides the strongest evidence to date for a link between VD deficiency and cardiovascular mortality. Vitamin D deficiency is associated with an increased risk of new onset coronary artery calcification, a finding that may help explain why cardiovascular events and deaths are more likely in individuals with VD deficiency. This association is stronger in patient with impaired kidney function.
Low VD levels also have been linked with several kinds of cancer and some researchers believe that VD could even be used to help prevent malignancies.
It is estimated that at least 50% of older adults worldwide have low VD levels and it is thought to probably affect substantial numbers of younger people as well. Possible reasons may be decreased outdoor activities, air pollution and as people age, a decline in the skin’s ability to produce VD from ultraviolet rays.
The daily requirement of this vitamin in adults is 400 to 600 international Unit. For chronic kidney disease patients much higher doses of up to 50,000 IU (Drisdol) is prescribed either weekly or monthly depending on the level of Vitamin. Hemodialysis patients are requiring it either once or twice a month to prevent deficiency as long as they are on dialysis.
In conclusion, in light of the recent discoveries, role of Vitamin D is taking much more significance. As a Nephrologist, I am required to check Vitamin D level on every patient with abnormal kidney function and correct the deficiency if found.
[Dr. Anis Ansari, MD is Board certified Nephrologist and Medical Associate, Clinton, Iowa, USA]