Does Vitamin D prevent the flu?
Influenza (flu) epidemics occur in winter, and rarely if ever in the summer. Vitamin D levels in humans are lowest in the winter, and highest in summer. Is there a connection, and does vitamin D prevent the flu?
Consider the following chart, taken from a paper, Epidemic influenza and vitamin D, which shows the percentage of all cases of type A influenza by latitude and month. Virtually all cases occur in winter and early spring, and none in the summer.
Next, the seasonal variation in vitamin D blood levels in people aged 50 to 80 in southern Germany.
There’s a clear correlation between vitamin D and influenza. But is it causal?
Probably.
I can’t find the report anymore, but for some reason they gave 35,000 IU to diabetics in a diabetes clinic. (That’s over 50 times the RDA, and nearly twice peak natural production.) A flu went through the clinic, except only the nurses got sick, not the patients. Notably, diabetics suffer a penalty to their immune function.
When I tried it, I found 8000 IU attenuated cold symptoms and at 10,000 it’s hard to even tell whether I catch them at all.
Coincidentally, a recent study found a statistical error in the RDA calculation, and their re-calculation suggests the RDA should be 9000. The current ‘safe’ upper value is 4000.
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At 10,000 IU daily, isn’t there a risk for kidney stones?
Source. You can find similar numbers elsewhere.