We all change habits
in the winter time, shifting activities indoors due to weather and shorter
daylight hours. Is it a
coincidence that the peak flu season is in the mid winter months? Apparently not.
A very interesting article in Epidemiological
Infections covers the history of thinking and investigation about the
subject and concludes that there is a very strong correlation with lack of
ultraviolet radiation exposure on the skin and incidence of the seasonal
flu. It is well worth reading if
for nothing other than an interesting graphic showing a completely inverse
relationship to skin UV exposure (and hence Vitamin D production), and the flu.
Our skin synthesizes
Vitamin D when exposed to the Sun’s UV radiation, however the Office of Dietary
Supplements of the National Institutes of Health point out that the sun screen
protection (SPF) we all apply in order to avoid skin cancer (don’t we all use
it?) can affect Vitamin D production.
In fact, SPF above 8 completely blocks
Vitamin D synthesis.
That said, I
advocate using a high SPF sunscreen, generally in the range of an SPF 30 to 50
because it is generally thought to limit UV damage to skin, and hopefully lower
our chances of developing skin cancer.
However, since this will significantly reduce Vitamin D production, it
is necessary to add a dietary supplement.
A good natural
source of Vitamin D is Cod Liver Oil.
However, for those non-fish oil lovers, any off the shelf source of
Vitamin D-3 will do.
While the original
recommended daily dose of Vitamin D was 400 iu, the FDA increased to 600-800 iu its recommended
daily dose depending on the population age. The Mayo Clinic article on Vitamin D
recommends a maximum safe limit of 10,000 iu.
So, it is not a
coincidence that we tend to start getting the winter flu in November, and it
peaks in February. Let’s try to
make our Vitamin D levels stable throughout the year and see if we can beat
that.
