Friday, October 02, 2009

Vitamin D, influenza, and old ladies

Many epidemiologists now believe that flu is seasonal because vitamin D levels fluctuate seasonally. Vitamin D is a potent immune modulator; individuals tend to have higher levels during summer months with higher exposure to UV radiation and, therefore, are less likely to contract the flu while sun-kissed.

Researchers followed the seasonal health adventures of 208 post-menopausal women over three years as correlated with their monitored intake of D.(1) The results, shown in the bar graph above, were as follows:
  • Those ladies in the placebo group (lightest bars) got cold and flu symptoms all year long, but especially in the winter.
  • The test subjects (intermediate shaded bars) who received 800 units/day of supplemental D were as likely to get sick in the summer as winter, but were far less likely to take to their beds than their D-ficient colleagues.
  • In the final year of the study, the test subjects were plied with 2000 units of D each day. Only one lady (as represented by the itty-bitty dark bar in summer) got sick while D-eeply dosed with the vitamin.
Presumably D same benefits accrue to old guys too.
1)Aloia JF, Li-Ng M: Epidemic influenza and vitamin D. Epidemiol Infect 2007; 135: 1095–1096.


kenju said...

I take 100 units of D per day. Should I up it to 2K?

femail doc said...

Absolutely. I've had patients who regularly take 400 IU per day (the amount in a multi-vitamin) whose D levels are so low the lab can't even find any at all on testing!

Reality Man said...

Very interesting. 2000 IU is what I am getting in my multi now that I am no longer relying solely on being a sun-drenched dirty guy.

dorsey said...

I'm taking 2 to 3 thousand a day specifically to be a test case re. flu. (I'd say it's to help my brain, too, but I've had to re-type almost every word). So far, so good.

Mauigirl said...

Very interesting. I'll tell my mom and aunt to up their D dosages! And here I thought flu seasonality was because the cold weather killed the viruses!