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Health Report from
Dr. Terry Smith
Vitamin D
For years many of us have thought of vitamin D only as it relates to bone health. However, research in the past several years have shown that vitamin D is involved with much more than that. There are vitamin D receptors on many cells in the body and most interestingly lymphocytes, which are our immune cells.
There is a significant growing body of evidence that Vitamin D is a hormone and not a vitamin. Certainly it is important in regards to calcium absorption and bone health, but probably much more importantly it modulates the immune system.
Vitamin D deficiency has been associated to some degree with the following medical problems: Type 1 diabetes, asthma, multiple kinds of cancers, multiple sclerosis, congestive heart failure, chronic pain syndromes, fibromyalgia, falls in the elderly, and the list goes on.
Evidence out of Scandinavian countries have shown that the mother's vitamin D status while she is pregnant, and whether the baby gets a significant increase in dose in vitamin D compared to what we normally give, may determine whether that baby develops Type 1 diabetes or asthma. (NEJM.2007 Jul. 19;357[3]:266 - 81.)
For many years the standard reference range for vitamin D levels from laboratories was 8 - 40 nanograms per milliliter. This was based on very little research. It was mostly determined by measuring the vitamin D in a lot of otherwise "healthy" people and developing a bell-shaped curve, which was called the reference range.
Evidence in the past few years has shown through research that the vitamin D level needs to be a lot higher. For the past couple of years the "reference range" for vitamin D has been raised to 32 - 100 nanograms per ml. (J.Nutr. 2005 Feb;135[2]:317 - 22.)
If you look on the side of a vitamin bottle it is going to say that 400 international units is 100% of the RDA. Unfortunately, this is not correct in my opinion. Medicine over the years has tried to get a set dose of vitamins and minerals for the average person in the population but has never individualized the doses based on each person's blood work or genes. Nowhere else in medicine, i.e. treating blood pressure, cholesterol, diabetes, would we give a single, set dose of a prescription for every single person and never follow-up on it and adjust it through laboratory or other measurements.
There are two types of vitamin D blood tests. The one we are talking about of most importance is the 25-hydoxy (25-OH) vitamin D level. This is the one that should be measured for most people. The 1,25-vitamin D level is important in calcium metabolism and is low in certain patients with chronic renal failure and sometimes high in patients with sarcoidosis.