Harvard Health Letter

9 things that can affect your vitamin D level

Weight, warm skin, and the angle of the sun are among the determinants.

When an Institute of Medicine (IOM) panel made long-awaited vitamin D recommendations late in 2010, one of the messages was that most Americans probably have enough of the vitamin circulating in their blood to get its main proven benefit, protection of bones. But in 2011, the National Center for Health Statistics released data that paint a less rosy picture. According to the center's numbers, almost one in three Americans has vitamin D blood levels below 20 nanograms per milliliter (ng/ml), the threshold that the IOM panel said is needed for good bone health. Besides, many experts think the IOM panel was too cautious and that we'd be better off if our vitamin D levels were considerably higher than 20 ng/ml.

The IOM panel may have put a damper on testing people's vitamin D levels, but that doesn't mean that vitamin D levels have suddenly become unimportant (or that many doctors don't order the tests anyway). And it doesn't mean that the science suggesting multiple benefits from vitamin D has been swept away.

To continue reading this article, you must login.
  • Research health conditions
  • Check your symptoms
  • Prepare for a doctor's visit or test
  • Find the best treatments and procedures for you
  • Explore options for better nutrition and exercise
Learn more about the many benefits and features of joining Harvard Health Online »