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Dear Lucy: I’m a healthy 40-year old male. After my doctor tested my vitamin D levels a few years ago, he insisted that I begin taking vitamin D supplements, which I did. At my check-up last year, my level had climbed from 25.3 to 54.7 nanograms per milliliter, which the doctor pronounced satisfactory, telling me to continue with the supplements. 

In talking with friends and colleagues of all ages and both sexes, I’ve found that virtually all of them have had the same experience of being tested for Vitamin D, being told they were deficient, and then being told to take supplements.

From the beginning, I’ve had my doubts that these supplements are necessary. Vitamin D is already added to milk and orange juice. I’ve also read that, as a redhead, I am more efficient than others in producing vitamin D. I wondered if we were all just being conned into giving more money to testing laboratories and vitamin manufacturers. Then, last spring, I read an article in the New York Times that bolstered my suspicions. According to this article, very few people are vitamin D deficient and, for healthy people, there is no particular benefit to having blood levels above 20 nanograms per milliliter. In fact, the article concluded that for healthy adults, there is no reason even to test vitamin D levels in the first place.

The Times reports that a huge, randomized study will conclude this year, so we should have more data soon. But, in the meantime, what is MIT Medical’s position on vitamin D testing and supplementing, and what evidence supports that position? Personally, I’ve stopped spending money on vitamin D supplements, but I’m open to changing my mind. Can you convince me that I should start taking these supplements again? —Agnostic


Illustration of a television with text displayed on the screen: 'Mythsmashers: Do you need vitamin D?'

Dear Agnostic: Thank you for a fascinating question! Like you, Lucy is always curious about the evidence supporting health and nutrition recommendations—and the quality of that evidence. You and the Times raise some interesting questions about vitamin D, so, when Lucy took this question to Associate Medical Director Patrick Egan, she was very much looking forward to getting a definitive answer.

Alas, it was not to be. 

“Vitamin D remains a conundrum,” Egan tells Lucy. “We doctors are not sure exactly who needs it, what the right level is, who should be tested, who should use supplements, or even what benefits Vitamin D has on a whole range of non-bone issues.”

He continues, “The Times article has it about right. For folks with fair skin, no gastrointestinal problems, and no particular restrictions on their ability to get some sun, we don’t even need to test. There is no reason to suspect that these individuals would have low levels, and there is no evidence that supplementing improves any outcomes — like reducing fractures from weak bones.”  

But, Egan says, vitamin D levels may be a legitimate concern for some patients, including healthy infants, older women, and people with darker skin—especially those who can’t, or don’t, go outside much. That includes certain members of the MIT community who spend all day in the lab, venturing outside only after dark. “I discuss, and often test for, vitamin-D levels in patients like these,” Egan explains. “Although it’s not clear that this is the best strategy, I have been finding folks with very low levels, and it seems to me that these patients—the ones whose tests come back as “deficient”—are the ones who will benefit from supplementation, rather than others who test as “borderline” or “insufficient.”  

MIT Medical does not yet have an official standard of care for Vitamin D testing or supplementation, according to Egan. “Most providers at MIT Medical take a similar approach to mine,” he says, “but, at this point, all of us are waiting for some kind of solid information about the issue.”

And, it seems, the rest of us will have to wait as well. Given what we know now, it doesn’t seem that Dr. Egan would try to change your mind about resuming supplementation. But, as we’ve all noted, more reliable data should be available later this year, and Lucy has extracted a promise from Dr. Egan to revisit the topic at a later date, when we know more. Stay tuned! —Lucy

Back to Ask Lucy Information contained in Ask Lucy is intended solely for general educational purposes and is not intended as professional medical advice related to individual situations. Always obtain the advice of a qualified healthcare professional if you need medical diagnosis, advice, or treatment. Never disregard medical advice you have received, nor delay getting such advice, because of something you read in this column.