Can vitamin D supplements prevent colds?

The Pediatric Insider

© 2017 Roy Benaroch, MD

Linus Pauling was a brilliant scientist. He won the Nobel Prize in Chemistry in 1954 (and, later, a Nobel Peace Prize for his work towards nuclear disarmament.) In the later part of his career, he became convinced that megadoses of vitamins, especially vitamin C, could ward off upper respiratory infections and other ills. Studies have never supported those claims. But maybe he was only off by one letter of the alphabet.

A recent, large study from the BMJ provides solid support for the use of vitamin D – not C, but D – supplementation to prevent ordinary colds and other respiratory infections.

There’s been some inkling that this might be the case. We know that vitamin D, separate from its role in calcium metabolism, has an important part to play in our immune response to infections. It supports the production of built-in antiviral and antibacterial peptides, and helps immune cells make germ-destroying oxygen and nitrogen compounds. Population studies that have shown an increased susceptibility to colds among people who are immune deficient.

What we haven’t had, until now, is a convincing study from an experimental perspective. If we give vitamin D, does that really prevent colds?

What these authors did was impressive. They collected the raw, patient-by-patient data from 25 previous clinical trials of vitamin D, and combined all of that into one mega-study with about 11,000 participants. All of the patients had to have been randomized to either vitamin D or placebo, and rates of respiratory infections tracked going forward. Most of them had blood tests to assess their levels of vitamin D before the trials began.

The bottom line: vitamin D supplementation decreased the risk of a cold by about 12%. That doesn’t sound very high, but on a population level, we’re talking about a lot of infections. And: among those that had low vitamin D levels, the effect size was much larger, about 40%. Vitamin D supplementation was more effective in preventing colds with a daily dose rather than just bolus dosing once in a while.

Who’s low in vitamin D? Based on my experience looking and blood tests from children and teenagers, all of our children are low. Seriously. The only time I see blood tests reflecting a normal or high vitamin D level, it’s in someone already taking a supplement. Our children (us, too) aren’t spending enough time outside to make the vitamin D we need.

The study also found no downsides to ordinary supplements. There were no significant side effects or problems. We’re talking, here, about ordinary doses of probably 400-2,000 IU each day. There’s really no reason to take any more than that, unless there’s a problem with vitamin absorption or some other unique medical issue.

Vitamin C, Airborne, zinc, echinacea – none of these have held up to scrutiny. None of those help prevent people from getting respiratory infections. If you want you and your children to get fewer colds, there are only a few strategies that genuinely work. Stay away from sick people, keep infants out of group care, wash hands frequently, and immunize against influenza and other respiratory pathogens. And, maybe, enjoy a little more time in the sun, or take a vitamin D supplement every day.


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5 Comments on “Can vitamin D supplements prevent colds?”

  1. Steve Auer Says:

    Paul Dean is a big Vit D booster.

    Takes large doses every day He thinks it is the miracle drug.

    On Mon, Feb 20, 2017 at 7:43 AM, The Pediatric Insider wrote:

    > Dr. Roy posted: “The Pediatric Insider © 2017 Roy Benaroch, MD Linus > Pauling was a brilliant scientist. He won the Nobel Prize in Chemistry in > 1954 (and, later, a Nobel Peace Prize for his work towards nuclear > disarmament.) In the later part of his career, he became” >


  2. Dr. Roy Says:

    I’m not sure who Paul Dean is — but vit D can be toxic in “large doses.” Vitamins are good, but there’s no reason to think huge doses are extra-good.


  3. Jenny Anglin Says:

    Hi Dr. Roy, I generally try to avoid vitamins and supplements for me and my kids since they aren’t regulated and I have no idea what’s in them. Can you recommend a brand or type that is more likely to actually have vitamin D (in roughly the advertised amount) and no arsenic or other unsavory ingredients? I’d love to start giving vitamin D because of the purported benefits, but want to make sure I’m doing more good than harm.


  4. Dr. Roy Says:

    Jenny, there’s a discussion of this very issue over on a post about melatonin, in the comments:

    “USP” seems like a reliable marker for quality supplements, and there are a few vitamin Ds on the list. Including the one I use, from Costco!


  5. Dr. Roy Says:

    Here’s a more-recent study that doesn’t support using Vit D to prevent colds:

    This study compared regular dose to higher dose D supplements, and found that kids in both groups had about the same number of colds. But there was not a comparison group without any D given. I think it remains likely that Vit D supplementation of children who are deficient may prevent colds — though if you’ve already gotten enough, extra won’t help any further. That fits the findings of both of these studies.


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