Back to sun exposure and vitamin D3 production. How much vitamin D3 can we produce? The figure is 10,000-25,000 IUs in 30 minutes though this is for light skinned individual. This is after 30 minutes of full midday sun exposure during the summer. That is with no clothes and 15 minutes full sun exposure to their front and then back. I have not been able to find out what really happens after these 15 minutes.
Does the vitamin D3 production magically stop or possible even reverses. Hardly, rigorous science on my part in using these estimates to calculate vitamin D3 production but I believe a rough estimate. If even close to accurate, then I would hardly call 2,000 IUs/day a high dose.
I tried to find a reference on skin production, but the ones I found were all over the place and I could, probably should write a blog posting just on how they calculate vitamin D3 skin production. See skin type (amount of melanin), amount of skin exposed and for how long and amount of UVB available all factor in.
Those living on the equator are said to be able to produce 30,000-40,000 IUs a day according to an article I read in the journal Science years ago. No, I can’t find it, so perhaps dreaming but doubt it. But this makes sense.
As those who live near the equator during the over the course of the year the sun angle changes very little as does UVB exposure available. Thus those who live there could potentially produce this amount of vitamin D3 year round.
In Northern and Southern hemispheres, the further from the equator the greater the is the angle of the sun as the closer is the day to the winter solstice and thus longer periods of reduced or no UVB light and thus reduced or no vitamin D3 production from the sun.
For example, over a calendar year, in Anchorage, Alaska there is much less cumulative UVB exposure then in New York City, all things being equal. Thus, all things being equal those in Anchorage would produce less vitamin D3 then do those in New York City.
Of course, many areas around the equator and in what I call the golden band (area between tropic of cancer and Capricorn) do have a rainy season when UVB is substantially reduced for prolonged periods of time.
Many factors, as what I discussed above is just the type of the iceberg, reason more study with doses that are optimal is needed and why fully understanding vitamin D3 production is complex. The point is, as I argue in my book and here 2,000 IUs is anything but a high dose. That alone negates the value of the VITAL study.
*The information posted above is for educational purposes only. Always check with your doctor before initiating any changes in your medical treatment. If you do not, then The Two-Minute Health Fact, Dr. Judson Somerville, nor The Optimal Dose is responsible!