DNC News

Vitamin D and Influenza

Jacob Schor, ND

November 5, 2006


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“Whoever wishes to investigate medicine properly should proceed thus: in the first place to consider the seasons of the year …”

Hippocrates (circa 400 B.C.)



The hallmark clue to vitamin D deficiency disease is an associated seasonal and latitudinal variability in incidence and morbidity. Multiple sclerosis, almost absent close to the equator increases in frequency the further from the equator one lives. Heart disease is worse in the dark winter months, blood pressure increasing as vitamin D stores in the body decrease. Similar associations are seen in the list of suspected disease caused or closely associated with low vitamin D which include diabetes mellitus, most forms of cancer, hypertension, myocardial infarcts, inflammatory bowel disease, and of course osteomalacia. But up until this December, no one dared to point their finger at the most obvious suspect of all, influenza and the common cold.




In its December 2006 issue, Epidemiology and Infection published a paper about vitamin D that is a must read for everyone in our profession. John Cannell of the Vitamin D Council, is the lead author listed, but the coauthors are all prominent vitamin D researchers. No subservient grad students are on this list: the co-arthurs include all the big names: Vieth of Mt Sinai in Toronto , Umhau of NIH, Holick of Boston University, Grant of SUNARC, Madronich of the National Center of Atmospheric Research, Garland of UC San Diego, and Giovannucci of the Harvard School of Public Health. They all stepped forward with Cannell and pointed out what should have been obvious all along; decreasing vitamin D levels during the winter trigger the seasonal cycle of cold and flu.


Edgar Hope-Simpson (1908-2003):

The paper begins by summarizing the later work of Edgar Hope-Simpson. Hope-Simpson was an English general practitioner, a self-educated epidemiologist, who has been long famous for his work in the 1940's and early 1950's. He figured out the cause of shingles linking it to the varicella virus through epidemiological analysis. In his later years but still, a quarter of a century ago, he turned his attention to influenza. “In 1981,” to quote Cannell, “Edgar Hope-Simpson proposed that a ‘seasonal stimulus' intimately associated with solar radiation explained the remarkable seasonality of epidemic influenza.” Hope-Simpson's 1992 book, The Transmission of Epidemic Influenza , summarized his findings and made an eloquent plea for scientists to identify this ‘stimulus'. As Amazon.com currently lists this book for $122, eloquent or not, it's not in my shopping cart. [leave that to Alex]


To quote Cannell, quoting Hope-Simpson:

“Hope-Simpson was the first to document that influenza A epidemics in temperate latitudes peak in the month following the winter solstice. ‘In both hemispheres, influenza rates rise significantly for about 2 months on either side of its peak. Outbreaks are globally ubiquitous and epidemic loci move smoothly to and fro across the surface of the earth almost every year in a sinuous curve that runs parallel with the midsummer curve of vertical solar radiation, but lags about six months behind it … Latitude alone broadly determines the timing of the epidemics in the annual cycle, a relationship that suggests a rather direct effect of some component of solar radiation acting positively or negatively upon the virus, the human host, or their interaction … The nature of the seasonal stimulus remains undiscovered….'”




Although Edgar suspected a seasonal trigger associated with changing ultraviolet light exposure, he didn't live long enough to identify it as Vitamin D. Cannell and colleagues nominate vitamin D deficiency as the mysterious trigger. They argue this nomination by pointing out a series of circumstantial clues. While Hope-Simpson suspected that some part of human physiology responded to ultraviolet light affecting immunity, he didn't have the benefit of our current knowledge of vitamin D biochemistry. If he had, he would have surely figured this out for himself. We now know that:


1. Vitamin D has profound and multiple effects on human immunity.

2. Vitamin D levels fluctuate over the year, more so in the higher latitudes and that deficiency is common, more so in the winter. Yet seasonal variations in D status occur even in tropical and subtropical latitudes.

3. Vitamin D deficiency is common especially among the elderly in the winter. The elderly only make about 25% of the vitamin D as 20-year-olds do after exposure to the same amount of sunlight.

4. Influenza occurrence parallels vitamin D deficiency in time and space.


If you are interested in the details of how vitamin D deficiency weakens immune function and enjoy brandishing words like, chemokines, defensins and cathelicidins in conversation, I definitely encourage you to read the original papers. Suffice to say that researcher have now elucidated much of the chemistry involved.


Norwegians, who get less sun exposure than any other Europeans, appear somewhat exempt from annual wintertime flu epidemic and have a smaller wintertime spike in mortality. The explanation is simple. Norwegians take fish oil, so much fish oil that they have the highest wintertime vitamin D levels of any European nation.


Disease from Outer Space?

Solar flare activity on the sun affects influenza outbreaks here on earth. Hope-Simpson, was the first to notice this association. Such an outlandish idea has justifiably, had its share of disbelievers. Although one proposed explanation suggests viral invasions from outer space, we now understand what is going on. Solar flare activity increases high-altitude ozone, which, in turn, absorbs more solar radiation and so decreases the amount of ultraviolet light that actually reaches the earth's surface. Current analysis says ultraviolet exposure may drop as much as 13% during maximum solar flare activity, something that fluctuates on an 11-year cycle. This fluctuation produces a proportional decrease in global vitamin D status. Extraterrestrial events may explain the cycles of more and less aggressive influenza epidemics. Wow!


Race Relations:

Melanin in the skin lowers vitamin D production. No one doubts that African Americans have lower vitamin D levels than white Americans. This fact is the simplest explanation as to why black children get pneumonia twice as often as white children. It also explains why blacks are more likely to die of respiratory infections and pneumonia.


Don't volunteer:

There are a number of trials in which people were injected with attenuated flu vaccine and then watched to see how many of them got feverish. It is not clear what incentives researchers employed to find these study participants; I would not rush to volunteer for this one. Anyway, it turns out that injecting people with flu virus produces very different results depending on when and where you perform the experiment. If you run the experiment in the winter, 8 times as many test subjects get a fever than if you run the same test in summer. The further north you run the experiment, the more people get sick at any time of the year.


John Jacob Cannell, MD

More examples:

Cannell points out no end of interesting trivia that associates D deficiency with upper respiratory infections. For example, children with Rickets, the classic vitamin D deficiency illness in which inadequate calcium is absorbed to build bones, are 11 times more likely to have lower respiratory infections than matched controls without Rickets.


Another example is a 1990 Russian study in which athletes were treated with ultraviolet radiation twice a year for three years. Compared to a matched control group, the treated athletes developed half the respiratory infections, recovered faster and had higher levels of salivary immunoglobulin.


These days we promote fish oils for their anti-inflammatory action. Years ago, the focus was different; fish oil was an anti-infective, given to reduce incidence of respiratory infections. Controlled studies from way back in the 1930's, show fish oil, which supplied a decent dose of vitamin D, reduced respiratory infections by 50%.


By this point, you should be getting the idea. You should download and read Cannell's paper: http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=469543



Read the full paper and then, sit down and contemplate those basic lessons we learned in naturopathic philosophy. Recall that debate between germ theory and fertile field that was so elementary to our medical education. As naturopaths, we view the concept that a fertile field is necessary for disease to occur and this remains an ongoing and central theme to our approach to preventing and treating disease. Yet, one rarely hears mention of fertile fields in modern medical literature, rather the focus is always on germs, the infectious agents responsible for causing disease. Cannell's paper lays out a perfect example and explanation for the fertile field. Both the cause and the cure for seasonal influenza are life style. Inadequate exposure to one of the most basic elements of nature cure, sunlight, weakens the body leaving it vulnerable to disease. Feel a little smug if you must.


Will vitamin D be the cure for the common cold? Or at least prevent the common cold? The jury is still out but the evidence is good enough that the question has been asked.



Every year, we all field patient questions about flu shots. This study must now inform how we answer those questions. Flu shots expose a person to a weak relative of the soon to arrive flu virus, stimulating the immune system to respond and acquire immunity. This has benefit as long as the drug makers pick the right virus strain for the vaccine. Vitamin D, in contrast, prevents flu by stimulating innate immunity and prevents flu infection, regardless of what strain arrives this year. Flu vaccine attempts to fight the germ. Vitamin D removes the fertile field. This is what naturopathic medicine is about.



Cannell JJ, Vieth R, Umhau JC, Holick MF, Grant WB, Madronich S, Garland CF, Giovannucci E.   Epidemic influenza and vitamin D.

Epidemiol Infect. 2006 Dec;134(6):1129-40.

Epub 2006 Sep 7.

PMID: 16959053 [PubMed - in process]




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