Vitamin D and swine flu prevention — shining a light on seasonal flu bugs

Nutrition & bone health

susanDid you ever stop to wonder why we have a “cold and flu season” — that is, why do we tend to get these illnesses in the cold, dark winter? And surely you have noticed that some people are resistant to colds and flu even while others around them are coughing, hacking, and spreading the virus like mad. As science now tells us, the answer, or at least part of it, lies in the sunshine vitamin known as vitamin D.

For years we thought of vitamin D as just another vitamin, but now we know that vitamin D is much, much more. This “vitamin” is really a hormone precursor — it is the stuff the body uses to make a potent hormone known as calcitriol, a hormone capable of signaling over 1000 genes to express or suppress themselves. Our bodies turn the vitamin D we produce — from sunlight exposure or in our diet — into this potent hormone that not only keeps us alive by regulating blood calcium, but also directly influences the functioning of every organ system. The heart, kidneys, gut, lungs, and yes, the immune system, are all influenced by the vitamin D hormone. Your risks of fracture, heart attack, TB, depression, periodontal disease, multiple sclerosis and many other auto-immune diseases, and, as it now appears, even the flu are dramatically lowered if you have optimal vitamin D blood levels. Overall mortality, in fact, is significantly reduced — by 8% — with even modest vitamin D supplementation. Activated vitamin D (calcitriol) is a complex hormone with as many mechanisms of action as the 1000 human genes it regulates.

How “the antibiotic vitamin” improves immunity to the flu

Reams of data have been published in the past decade, documenting the role vitamin D plays in nearly all bodily systems, and the immune system is no exception. As researchers report, the evidence that vitamin D has profound effects on the part of the immune system known as innate immunity is growing fast — a recent article in Science News even tagged vitamin D as the “antibiotic vitamin.”

Innate immunity is the heart of our defense system that is “hard wired” to respond rapidly to microorganisms using genetically encoded response mechanisms. These innate immune system responses include the production of broad-spectrum antimicrobial agents known as antimicrobial peptides (AMP’s). Epithelial cells (skin cells and cells that line our internal passageways) and a wide range of immune cells (such as macrophages) create these natural antibiotic AMP’s upon exposure to microbes. This action, however, is dependent on the presence of vitamin D! This means that our bodies produce their own “homemade” antibiotics — some 200 different types — all of which are up-regulated and stimulated by the active vitamin D hormone. These homemade antibiotics attack and irreversibly damage a wide range of fungi, bacteria, and viruses.

Vitamin D and influenza: the data

Seasonal variation in flu and vitamin D

It’s commonly held that influenza is a highly infectious virus spread by the sick to those who are well. Many people also assume that the virus is spread more easily in the winter because that’s when everyone is “huddled together” indoors.

Decades ago, however, a noted scientist questioned these assumptions and went on to propose that there is an unidentified “seasonal stimulus” associated with flu outbreaks.

As this physician, Dr. Hope–Simpson, documented over and over again, flu incidence was tightly correlated with the winter season, and it was not consistently spread from ill to well after all.

Indeed, we all recognize that there is a flu season — the dark wintertime — but we have also witnessed that not everyone who is exposed to the virus gets sick.

It is now becoming clearer that low wintertime levels of vitamin D — the sunshine vitamin — may indeed be the “seasonal stimulus” that triggers flu outbreaks and influences individual susceptibility to influenza infection.


The story of the vitamin D–influenza link is actually telling the tale of the work done by Dr. John Cannell. I have been in personal communication with Dr. Cannell over a number of years and have carefully followed his work and that of his non-profit Vitamin D Council.

When I first spoke with Dr. Cannell several years ago, he told me about his work as a psychiatrist at the Atascadero State Hospital in California. Interested in vitamin D, and suspecting common vitamin D deficiency among his inmates, Dr. Cannell regularly tested inmates for vitamin D adequacy. As he expected, he found they had abnormally low levels of vitamin D and, after explaining the benefits of this vitamin, he prescribed for the inmates 2000 IU vitamin D3 (cholecalciferol) a day.

In the late winter of 2005, a virulent strain of influenza hit the maximum-security psychiatric hospital, and although 10% of the 1200 patients ultimately developed the flu’s fever and debilitating muscle aches, there were, no cases of flu among Dr. Cannell’s inmates Dr. Cannell’s, who had been given daily vitamin D supplements. In a 2006 interview, Dr. Cannell said, “First, the ward below mine was quarantined, then the wards on my right, left, and across the hall.” And even though Cannell’s inmates had mingled with the others prior to quarantine, they still managed to avoid the flu.

How was it that his inmates were able to dodge the flu? A few months later, he came across a scientific report stating that vitamin D was found to increase the production of natural antimicrobial compounds in white blood cells. It was then that Dr. Cannell’s “Aha!” moment occurred. Could it have been the vitamin D he routinely gave his inmates that protected them from the flu? Encouraged by his colleagues, Dr. Cannell and seven other noted vitamin D scholars reviewed more than 100 articles that — in one way or another — linked vitamin D with enhanced immunity and fewer respiratory infections.

The research reports that pointed to a D–influenza link included findings like these:

  • Many studies noted an association between rickets, the classic childhood disease of vitamin D deficiency, and increased respiratory infections.
  • A research comparison of 80 rickets-free children found that children with very low 25(OH)D levels (less than 10 ng/mL) were 11 times more likely to be infected with respiratory infections than children with higher vitamin D levels.
  • A 1994 study showed that intervention with vitamin D (60,000 IU a week) and calcium (650 mg/day) produced a significant reduction in the incidence of infections in children with subclinical rickets.

These early research findings, along with his own experience with his inmates, led Dr. Cannell to boldly suggest that vitamin D deficiency could underlie a vulnerability to influenza infection. Since the first article on influenza and vitamin D was published in 2006, a new body of research has developed that strongly supports the hypothesis that low vitamin D levels increase vulnerability to flu and that high vitamin D levels offer a protective effect.

In 2007, Dr. Cannell and colleagues published a second paper on the vitamin D–influenza connection in the Virology Journal. Here they explored 9 key questions including, “Why is influenza both seasonal and ubiquitous, and what happens to the virus between epidemics?” “Why are influenza epidemics so explosive?” “Why do they end so abruptly?” and so forth. An important part of the answers to each of these questions pertains to the fascinating role vitamin D plays in the enhancement of innate immunity.

A series of new studies lends growing support to the theory that low vitamin D levels increase vulnerability to influenza.

  • A study of young Finnish men in military service reported that those with a vitamin D deficiency had significantly more days when they were absent from duty due to respiratory infection than the servicemen who were not vitamin D deficient.
  • A Turkish study of newborn infants found that those with acute lower respiratory infection had lower levels of vitamin D (along with their mothers) than other newborns who were free of respiratory infection.
  • In a study of African-American women, self-reported symptoms of colds and influenza were more than three times lower in the women given 800 IU daily of supplemental vitamin D3 over two years than those in the placebo group. And this relatively low dose effectively abolished the seasonality of colds and flu. A higher dose of 2000 IU given during the last year of this three-year trial virtually eradicated all reports of colds and flu.
  • A very recent report in the Journal of Pediatric Research summarizes the scientific consensus that, in the face of vitamin D deficiency, infants and children appear more susceptible to viral infections than bacterial ones. They concluded that the now recognized connections between vitamin D, infections, and immune function suggest a role for vitamin D supplementation in the pediatric population.

Even more interesting than scientific study — real-life swine flu prevention with vitamin D

While the scientific studies connecting low vitamin D and influenza are interesting, what I find even more valuable and intriguing are the informal reports from clinical settings, where the use of vitamin D amongst patients was tightly linked to a reduction in their vulnerability to the most recent swine flu variant (H1N1). Two very interesting reports from clinical settings were submitted to Dr. Cannell and published in his Vitamin D Council Newsletter in September 2009. These reports help me see the real day-to-day value of vitamin D supplementation even more clearly than the scientific studies do.

The first report is from a doctor in Wisconsin, Dr. Norris Glick, who wrote to Dr. Cannell:

Your recent newsletters and video about Swine flu (H1N1) prompted me to convey our recent experience with an H1N1 outbreak at Central Wisconsin Center (CWC). Unfortunately, the state epidemiologist was not interested in studying it further, so I pass it on to you since I think it is noteworthy.

CWC is a long-term care facility for people with developmental disabilities, home for approx. 275 people with approx. 800 staff. Serum 25-OHD has been monitored in virtually all residents for several years and patients supplemented with vitamin D.

In June 2009, at the time of the well-publicized Wisconsin spike in H1N1 cases, two residents developed influenza-like illness (ILI) and had positive tests for H1N1: one was a long-term resident; the other, a child, was transferred to us with what was later proven to be H1N1.

On the other hand, 60 staff members developed ILI or were documented to have H1N1: of 17 tested for ILI, eight were positive. An additional 43 staff members called in sick with ILI. (Approx. 11–12 staff developed ILI after working on the unit where the child was given care, several of whom had positive H1N1 tests.)

So, it is rather remarkable that only two residents of 275 developed ILI, one of which did not develop it here, while 103 of 800 staff members had ILI. It appears that the spread of H1N1 was not from staff-to-resident but from resident-to-staff (most obvious in the imported case) and between staff, implying that staff were susceptible and our residents protected.

Norris Glick, MD
Central Wisconsin Center
Madison, WI

Dr.Cannell’s Comment:

This is the first hard data that I am aware of concerning H1N1 and vitamin D. It appears vitamin D is incredibly protective against H1N1. Dr. Carlos Carmago at Mass General ran the numbers in an email to me. Even if one excludes 43 staff members who called in sick with influenza, 0.73% of residents were affected, as compared to 7.5% of staff. This 10-fold difference was statistically significant (P<0.001). That is, the chance that this was a chance occurrence is one less than one in a thousand.

Second, if you read my last newsletter, you will see that children with neurological impairments, like the patients at your hospital, have accounted for 2/3 of the childhood deaths for H1N1 so far in the USA. That is, the CDC knows, because they reported it, that patients with neurological impairments are more likely to die from H1N1.

The second report is from a doctor in Georgia, Dr. Ellie Campbell, who wrote to Dr. Cannell:

Thanks for your update about the hospital in Wisconsin. I have had similar anecdotal evidence from my medical practice here in Georgia. We are one of the 5 states with widespread H1N1 outbreaks.

I share an office with another family physician. I aggressively measure and replete vitamin D. He does not. He is seeing one to 10 cases per week of influenza-like illness.

In my practice — I have had zero cases. My patients are universally on 2000–5000 IU to maintain serum levels 50–80 ng/mL.

Ellie Campbell, DO
Campbell Family Medicine
3925 Johns Creek Court
Ste A Suwannee GA 30024

I’m sure that as time goes by, you will find more healthcare providers reporting their experiences with vitamin D supplementation and flu. You can follow the compelling work of John Cannell by subscribing to the Vitamin D Council newsletter and you can also listen to Dr. Cannell discuss vitamin D and the flu on YouTube.

So what’s a person to do?

So far the US Centers for Disease Control (CDC) has not responded to requests from Dr. Cannell and colleagues that the US take a serious look at the link between low vitamin D and flu susceptibility. The Public Health Agency of Canada, on the other hand, is investigating the role vitamin D might play in protection against swine flu. But this research by the Canadian government, while moving in the right direction, will likely take years.

The flu season, on the other hand, is upon us and, given the safety of vitamin D and its likely benefits, it seems reasonable to hedge your bets and take in sufficient vitamin D to reach the suggested protective vitamin D blood level of 50 to 80 ng/mL 25(OH)D. This represents a vitamin D blood concentration consistent with that obtained from abundant natural summertime sunlight exposure. The amount of vitamin D needed to reach this ideal blood level varies from individual to individual, depending on sunlight exposure, vitamin D reserves, skin color, body fat, age, and the like.

As Dr. Cannell reports, most individuals will probably require somewhere between 2000 IU and 5000 IU vitamin D a day to reach the 50-80 ng/mL level. Luckily, with vitamin D we know the blood level we are striving for (50-80 ng/mL), so you can take 2000 units a day for eight weeks and then ask your physician to test your 25(OH)D blood level. Generally, every additional 1000 IU of vitamin D will raise your level about 10 points of ng/mL.

Wave goodbye to seasonal colds and flu

You don’t have to wait until you feel the symptoms of a cold or the flu coming on — you can begin today and build better immunity against colds and flu infections by supplementing with vitamin D. You may well find that seasonal colds and flu become distant memories.

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