Vitamin D supplementation found to help prevent flu in children

Back in February I wrote a post that was largely focused on my experience of supplementing with vitamin D, and specifically the fact that I had not had a single infection (e.g. cold or flu) since starting supplementation. I still, by the way, have not had an infection. Not even a hint of one. This might all be coincidental, but others (some of whom have commented on the site) do seem to have similar experiences. And given that there are plausible mechanisms through which vitamin D can afford relative protection from infection, there does seem to be mounting evidence that vitamin D can indeed help keep us infection-free.

This week saw the publication of a study which adds further support to the idea that vitamin D can help the body ward off infection. In a study, published in the American Journal of Clinical Nutrition, Japanese schoolchildren aged 6-15 years were treated from December through to the end of March with vitamin D (1200 IU per day) or placebo [1]. The outcome assessed was infection with the viruses influenza A and B (the two most clinically important of the three main types of influenza virus). As an aside, influenza A includes the H1N1 strain that last year was responsible for the ‘pandemic’ alerts of last year.

Whether a child had succumbed to influenza over the course of the study was tested microbiologically using swabs from the nose/throat.

Vitamin D supplementation was not associated with a reduced risk of infection with influenza B. However, for influenza A, the results were positive, with vitamin D reduces risk of infection by 42 per cent overall. The benefits were even more dramatic in children who had not been previously supplementing with vitamin D: in this group of children, risk reduction was 64 per cent.

Interestingly, in children with a history of asthma, there was no reduction in risk of flu virus infection. However, those taking vitamin D were at very significantly reduced risk of having an asthma attack.

What we have here is a placebo-controlled study which demonstrates that vitamin D supplementation has the power to protect against flu. This study, to my mind anyway, provides good scientific support for the anecdotal experiences of those, including myself, who have found that vitamin D supplementation has afforded protection against viral infection.


1. Urashima M, et al. Randomized trial of vitamin D supplementation to prevent seasonal influenza A in schoolchildren. Am J Clin Nutr 10th March 2010 [epub before print publication]

, , , , , , ,

13 Responses to Vitamin D supplementation found to help prevent flu in children

  1. Nigeepoo 12 March 2010 at 4:35 pm #

    The abstract doesn’t mention the children’s serum 25(OH)D levels before & after supplementation. Is that because they didn’t want to stick needles in children? 1,200iu/day isn’t very much (although it might be for small children) so that dose may have been sub-optimal.

    As for you, have you considered putting a big chart on your wall in full view of patients that shows how long you have gone without catching anything? That might encourage patients to start supplementing with Vit D3.

  2. Dr John Briffa 12 March 2010 at 6:28 pm #


    Vitamin D levels were not checked in this study (which is a shame, I think).

    I’ve no plans for a chart, though I might start talking about my infection-free record with patients a bit more…

  3. Mo 12 March 2010 at 8:50 pm #

    It’s likely that some damage has already been done to the immune systems of asthmatic children resulting in not as good an effect.

    By the way, I’ve been taking at least 5000IU D3 since 2008 and I have still neither had a single cold or flue. I only sneeze, once off, when dust enters my nose, but that’s it.

  4. Megan 12 March 2010 at 11:32 pm #

    Normally I have a flu jab every autumn, and normally I have colds, bronchitis or tonsilitis throughout the winter.

    This year I refused both flu jabs, started taking high doses of Vitamin D3 and coconut oil, and, touch wood, I have only had two tiny sniffles that didn’t last any longer than a day.

    I was very sceptical, but I’m totally convinced now!

  5. Jamie 13 March 2010 at 1:00 am #

    No baseline taken, and if using the common recommendation of 1000IU per 15kg of body, many of these children probably could have taken a higher dose. As Stephan Guyenet points out in his analysis, it may have taken the duration of the study for some of these children to build up vitamin D concentrations to a protective level. So the fact that they found a significant effect with some gaping holes in the study design, gives the findings even more punch in my book.

  6. Rox 13 March 2010 at 2:40 am #

    Has anyone else noticed cramp or pins and needles in hands since starting on vitamin D3? Is this because calcium absorption is increased in the presence of D3 and should I therefore supplement magnesium to prevent this? Now stopped the D3 but miss its mood-elevating effect.

  7. audrey wickham 13 March 2010 at 3:28 pm #

    On the other hand Megan, after many years of having the flu jab and not having a cold I forgot, because of pressures at work, to have a jab in 1991. The whole of that winter I was never without a cold. As soon as one cold finished another started. I don’t have pressures now – too old just a daughter who tells me constantly that the flu jab can’t have any relation to getting a cold. Nevertheless, although I might get up with the start of a cold – sneezes, runny nose, by 10 o’clock all symptoms have gone.

  8. Jess 14 March 2010 at 2:25 am #

    I’ve been taking 10-20k d3 for a year now, and still catch almost every cold going around the school. I get a decent amount of sun when I can as well. So it’s not a magic cure, even for someone following a primal diet.

  9. donald galfond 16 March 2010 at 5:42 am #

    Are there any large credible studies showing serious benefit, or harm, from vitamin D supplements?

  10. Dr John Briffa 16 March 2010 at 10:25 am #


    There exist a meta-analysis that found a reduction in risk of mortality. See here:
    Dosages of vit D in these studies was generally lower than is required for optimal vit D levels.

  11. Diane 10 May 2011 at 10:19 am #

    I have a child of 3 and a half and another of 1 and a half. this year the eldest one began school and is most of the time gettinng sick lately he is suffering from tonsillitis together with high fever. he was given some medicine for a seasonal allergy and antibiotics. His little brother is also getting sick and is taking puffs. I’m also suffering from tonsillitis every time they get sick. Can you advice me of what to do please? As soon as he starts school he is present for 4 days and is sick. is it true that this is what happens to children that start school?


  1. Garden of Life – Vitamin Code 50 & Wiser Women, 120 veggie caps : World Online Review - 13 April 2010

    […] Vitamin D supplementation found to help prevent flu in children … […]

  2. Nature Inspiration - 2 January 2012

    Recommended Resources…

    […]the time to read or visit the content or sites we have linked to below the[…]…

Leave a Reply