Vitamin D

Ask the DOC

Every few years there is a new fad in medical testing. A while ago it was homocysteine, then it was high-sensitivity CRP (C - reactive protein). Lately Vitamin D testing is all the rage.  Everyone, it seems, is ordering 25 hydroxy (OH) Vitamin D levels. But is there really a need to do Vitamin D screening on healthy patients? Unnecessary screening can lead to vitamin supplements and other testing, which raises the costs of health care.

Vitamin D is necessary for proper bone health. The most common source of Vitamin D is sunlight, but all reference levels and information about Vitamin D assume that there is no sun exposure as this assumption creates a common baseline. A few years ago, the Institute of Medicine (IOM) came out with recommendations on Vitamin D Recommended Dietary Allowances (RDA) and Vitamin D levels. The IOM report was in response to a number of studies that indicated that large swaths of North Americans were Vitamin D “deficient.” The evidence that was cited was that many people in these studies had levels of 25OH Vitamin D that were below 20 (ng per ml) or that supplements of Vitamin D of 600 to 800 IU daily failed to raise the level above 20. In fact, the IOM estimated that a level below 20 was actually appropriate for most people. To add to the confusion many labs use a reference level for 25OH Vitamin D of 30, making anyone below 30 “deficient.”

The main reason for the confusion is that many people misinterpret the Vitamin D RDA of 600 IU for those from one to 70 years old, and 800 IU for those over 70 to mean that these intake levels would correspond to a “normal” Vitamin D level. A daily intake of 600 to 800 IU would actually correspond to a 25OH level of 20. However, the reality is that the large majority of the population (about 97.5 percent) has a Vitamin D requirement of 20 or less and about half of the population has a requirement of 16 or less.

Therefore, the IOM recommends that a normal, healthy person does not require any Vitamin D supplements because a 25OH level of 16 to 20 is perfectly normal for them. Some people have risk factors for Vitamin D deficiency. These risk factors include osteopenia, osteoporosis, malabsorption, the use of certain medications that may interfere with Vitamin D metabolism (like anti-seizure medications), and institutionalization (nursing home). People with risk factors should be screened and given Vitamin D supplementation when appropriate. Most medical organizations recommend against Vitamin D screening for healthy individuals and against the use of Vitamin D supplements for healthy individuals. Those concerned about Vitamin D levels should choose foods that are fortified with Vitamin D (dairy products, cereals, etc.).

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