I am a fan of Steve Gibson, author of the SpinRite hard drive maintenance tool and the discoverer of "spyware". His web site at http://www.grc.com contains many valuable computer security articles and other freeware goodies. He also has a weekly podcast with Leo Laporte, hosted at http://twit.tv/sn and available free.
In August of 2009, Steve's "Security Now" podcast had one episode dedicated entirely to a very non-computer related topic, Vitamin D. I was interested by what was presented, and followed up with some more of my own research. I didn't follow through on any of it until later that winter... After my usual predictable second winter cold.
I usually can knock down a cold with Zicam in just a few days. But sadly my preferred mode of application (a nasal gel) was removed from the market mid-winter 2009, leaving me with inferior options. In late January 2010, I decided to make myself a guinea pig for my own flu and cold vaccine... vitamin D.
Considering the likely suspects for vitamin D deficiency, I fit the profile: technology worker who rarely goes outdoors, paranoia about sunburn with SPF 30+ as the norm when I do go outside, drink very little milk, and like most Americans don't eat enough fish. In direct sunlight, the human body can produce 10000 IU or more of vitamin D within an hour. I have been taking 5000 IU of vitamin D3 for the past 9 months, under the assumption that i was likely vitamin D deficient. This works out to the equivalent vitamin D I would get from daily sun exposure of an amount "halfway to a sunburn", or 4 tablespoons of cod liver oil.
I will be having a physical exam from my primary care physician shortly and plan to request a test for 25-hydroxy-vitamin D levels, to see if I am within the recommended range. But the real telling result will be the very typical colds I get every winter. I get at least one cold, and I have had the flu every three years or so. I am not a fan of flu vaccines, and consider this vitamin D experiment my own self-vaccination experiment.
I urge you to review the materials compiled at http://www.grc.com/health/Vitamin-D.htm and see for yourself. This is no quackery, but contains some of the usual suspects in the so-called real medical community stating that vitamin D might actually have benefits far beyond the prevention of rickets. I'll keep you posted with my own experimentation.
For what it's worth: I have not been Ill a single day since starting vitamin D in January 2010, and this included a February trip to Israel. If I get through the entire winter untouched by cold or flu, I will certainly be convinced there's something to this...