What’s All the Fuss About Vitamin D?

It’s been hard to miss a steady stream of headlines for years now about vitamin D in obesity and bariatric surgery. “Vitamin D deficiency is the cause of common obesity” is one such headline, found in the journal, Medical Hypotheses. So what is all the fuss about vitamin D?

To start, it’s reasonably clear that vitamin D deficiency is associated with obesity. But it’s not at all clear that the deficiency is causing obesity. In fact, a careful analysis published in PLOS Medicine concluded that the more likely explanation is just the opposite — higher BMI leads to vitamin D deficiency. This observation is consistent with earlier research showing that vitamin D — either from food or sun exposure — is less bioavailable in people with obesity.

Which leads us to the latest research in bariatric surgery, pointing to an association between lower vitamin D through sun exposure and more complications in bariatric surgery. This particular study, led by Leigh Peterson of the Johns Hopkins Center for Bariatric Surgery, can tell us nothing about causality, though it adds to our understanding of the importance of the subject.

Two other studies published this year also add to that understanding. Marlene Chakhtoura and colleagues have just published a systematic review that documents the persistence of vitamin D deficiency in bariatric surgery patients and the need for research to improve the regimens for supplementation. In September, Christian Muschitz and colleagues published a randomized study showing that vitamin D supplementation, along with calcium, protein, and physical exercise, can reduce bone loss following bariatric surgery.

What does all this mean? Clearly, it means that low vitamin D levels are a concern for people living with obesity. This is especially true for people having bariatric surgery. But testing for vitamin D levels remains controversial in primary care. Even though routing screening of vitamin D levels is recommended, Peterson says the recommendation is not widely followed by referring physicians:

Education for primary care physicians may be needed to truly improve screening of bariatric surgery candidates for vitamin D deficiency.

Whether you are caring for people with obesity or living with the disease yourself, a good understanding of vitamin D levels carries increasing importance.

Click here for more on the study by Peterson et al, and here for the study itself.

Bring Me Sunshine, photograph © Carl Jones / flickr

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January 4, 2016