Flu Season Secret Weapon: Vitamin D to the Rescue

Step aside vitamin C!  New research suggests that daily vitamin D supplement that may help prevent the flu, particularly in kids and teens.

We know that we’re more likely to get sick in the winter, and we also know that we get vitamin D primarily from sun exposure. Is this a coincidence?  One theory behind the seasonality of the flu is that lower levels of vitamin D during the winter lead to lower immunity.  Indeed, research has shown at least two ways in which Vitamin D boosts our immune systems.  First, it enhances the strength of our white blood cells, whose primary function is to fight off invaders — such as flu viruses.  Second, it has anti-inflammatory properties, which means that it can lessen symptoms when you have been infected with a virus.  Children are especially at risk for seasonal flu because their immune systems are less mature, and because flu can spread around a crowded classroom with ease.

In this study, 334 Japanese schoolchildren aged 6 to 15 were divided into two groups.  One group received a 1,200 IU vitamin D supplement daily for four months (December to March), while the other group received a placebo daily. Both groups were assessed for flu symptoms during the four-month study period.  Since regular vitamin D supplementation for three months is shown to stabilize vitamin D blood levels, the study’s four-month duration would presumably be long enough to observe a potential protective effect of the vitamin. And that’s apparently what the researchers saw: by the end of the four months, there were 42 percent fewer cases of seasonal flu in the children receiving the vitamin supplement compared to those on placebo. Furthermore, children with a previous diagnosis of asthma were 83 percent less likely to have an attack if they were taking the vitamin D supplement compared to asthmatic children taking the placebo.  This observation is consistent with the findings of a recently study we covered suggesting that vitamin D can help prevent asthma attacks.

As always, caution should be taken when interpreting these results.  The parents were instructed to bring the pill bottles to every follow up clinic visit so that the remaining pills could be counted.  This was how adherence to the program was measured instead of taking blood samples and analyzing for vitamin D level.  This is significant because that means there is no biological proof that the children in the test group had higher blood levels of vitamin D than the placebo group.  It should also be noted that this study’s dose of 1,200 IU Vitamin D exceeds the adequate intake for children currently established by the Institute of Medicine (200 IU).  However, experts widely regard this recommended level to be too low, and the American Academy of Pediatrics (AAP) advises at least 400 IU daily for infants, children and adolescents.  Furthermore, daily doses up to 2000 IU are considered to be perfectly safe by the Institute of Medicine for children aged 1 and older.

While getting a flu shot is still the best insurance against getting the flu, maybe popping a daily vitamin D supplement is another weapon we have in our battle to stay healthy this winter.

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  • I haven’t had a cold or flu in 4 years- not one- since I started taking my vitamin D health seriously.

    Not to mention, after a lifetime of sports, feeling 25 years younger.


    The optimal range of circulating vitamin D is 50-80 ng/ml, and not a nanogram less.

    Intake up to 10,000 i.u. per day (1/4 milligram) is perfectly safe and easily tolerated. Anyone, regardless of profession, who disputes this is simply not aware of the facts.

    FYI the human body makes 20,000 i.u. of vitamin D (precursor) in 15 minutes of direct sun if in a bathing suit.

    You know, the way we were intended?

    NOTHING matters more than vitamin D in terms of maintaing human health. It is the single most important health issue we face. Look at the facts, the new research findings, and be stunned to vitamin D deficiency and its STRONG connection to every early onset chronic disease.

    It is very clear that mainstream medicne missed it completely, that is, the importance of vitamin D and time in the sun. It makes more sense than anyone reading this can know. Nme a disease and see the links to vitamin D deficiency, either in pregnant mother, or grown adult.

  • Just the nagging academic in me, but you say “facts” and “mainstream medicne [sic]” yet provide no sources. I would love to read peer reviewable work or whatever else it is that has so devoted you to this regimen! Please share.

  • well i find this study interesting and it could be helpful for some people. On the other hand, im from a country which has a shiny sun all year ( even in winter the sun still little hot in the afternoon). That means that im full of Vitamin D, But i still get flu ..

  • vitamin D acts like a hormone. Be very careful in taking supplements. D is not water soluble and will accumulate in your body.

  • It is a vast over-generalization to say that the body makes 20,000 IU of vitamin D in 15 minutes of direct sun in a bathing suit. The amount of vitamin D produced due to sunlight depends also on the darkness of the skin, the latitude of the location where one is receiving direct sunlight (equator vs. in New York, for example), and many other factors. For 20,000 IU of sun produced vitamin D, a more likely sun exposure is several hours based on what I’ve gathered from “The Vitamin D Cure” by James Dowd, not 15 minutes. If you dispute this, please provide a source for your numbers.

  • Sunflower Seed is a very good source of Vitamin D-Complex. The extract is the best way to take it & am more than happy to talk to any one who wants more information.

  • Thats what you want, for it to accumulate…..
    I take 3000-4000 iu a day and had a blood concentration in the upper normal range, which is still too low according to Dr . Wiskers of Tuff University

  • Vitamin D is a hormone. And as Flores12got said, it’s -supposed- to accumulate. Stored in your fat to get you through the winter. Also, one needs appropriate magnesium levels/intake to convert the Vit D supplement into an active form.

  • The article is funny – you mean grandmas cod liver oil before the onset of winter is the solution, I thought we all knew that. I agree it is the most important item to use. Without enough vitamind D there is imparied calcium absorption and if one is taking liver affecting medications – which most of them are, calcium is being removed by them also. do you have any suggestions for what type of vitamin D is the best to take?

  • Im sorry my doctor a thyroid specialist said that 15 minutes int he sun replaces vitamin D that the body needs, so this writer is correct., unles you dont believe my doctor either

  • The human body can produce between 20K and 50,000 IUs of D in one day. That fact will be easy to find. What is very interesting to me is that the government only recommends 400 IUs per day. This has made millions of people vitamin D deficient.

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  • I took 4,000 IU of Vita D3 in gel form last winter and didn’t get sick from either the flu or a cold. New studies indicate Vita D3 good for asthma.
    Any sunny day in the winter, I go outside and get my “rays” for 15-25 minutes.
    My mom had asthma and both breast and colon cancers AND was Vita D3 deficient. When first diagnosed, I told her that she was deficient in something. Wish I’d known then what I know now as obviously she was lacking in Vita D3. She was also darker complected making absorbing sun’s rays even harder from the research I’ve done.

  • Some people do not make or absorb enough vitamin D, so it is not necessarily enough to get sun and take the recommended supplement. Also, there are other nutrients that help you absorb vitamin D (magnesium, zinc, boron, selenium, vitamin A, and vitamin K2) and the recommended form is vitamin D3, although doctors sometimes prescribe D2 for people with deficiencies. Check out the Vitamin D Council website for more information.

    My sister and I both had vitamin D deficiencies without knowing it. When I discovered it and started supplementing, I found that my joint, bone, and muscle aches went away, I felt better overall, and I got sick less often.

  • Hello Sonyatoler,
    I’m very interested in more information about the fact that Sunflower Seed is a very good source of Vitamin D-Complex .Could you please send me some more info.
    Greetz Moreno

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