Forget testing for vitamin D

We need vitamin D because it increases our intestinal absorption of calcium, magnesium, and phosphorus and makes our bones strong. We get most of the vitamin through a synthesis that occurs on our skin. The synthesis is a complicated process involving a chemical that resides in our skin combined with exposure to the sun (ultraviolet light). (Vitamin D is found in only a few foods, such as egg yolks, oily fish and milk fortified with vitamin D.) Because many people have little exposure to sunlight, especially those living in northern areas in the winter, some investigators became concerned that large swaths of the population were not getting enough of the vitamin.

In 2007, one influential doctor published a paper asserting that blood levels of vitamin D below 29 nanograms per milliliter of blood leads to an increased risk of cancer, autoimmune disease, diabetes, schizophrenia, depression, poor lung capacity and wheezing. (He’s also published books.) Word got around and soon “there was a vitamin D bandwagon,” in the words of Mayo Clinic doctor. Doctors began incorporating vitamin D tests into the general evaluation of patients. Commercial labs immediately began describing levels of 20 to 30 nanograms as insufficient (and many continue to do so). The number of blood tests for vitamin D among Medicare beneficiaries increased 83-fold from 2000 to 2010. Among those with commercial insurance, testing rates rose 2.5-fold from 2009 to 2014.

In the meantime, a number of scientists performed multiple studies to verify the doctor’s claim, which turned out not to be true. After conducting many trials with thousands of test subjects, scientists found that those who took vitamin D supplements were no better off than those who took placebos. After reviewing the studies, the Institute of Medicine prepared a report stating that there’s no benefit for healthy people to have blood levels above 20 nanograms of vitamin D per milliliter of blood. After becoming convinced that the tests weren’t necessary, one doctor tried to discourage her patients from being tested. But, she said, “people were used to vitamin D monitoring, like with cholesterol. They wanted to know what their number is.”

There’s no reason to be tested for vitamin D, even if you live in Maine. It’s just another unnecessary test.

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