The Vitamin D naysayers, including some so-called "experts", like to say that a little brief sun exposure is all it takes to supply the body's need for Vitamin D. However, that claim has never been put to the test- until recently.
Recently, Dr. John Cannell of the Vitamin D Institute reported on a study out of Korea. Dr. Sang-Hoon Lee and colleagues from the Ajou University School of Medicine in South Korea studied the effect of brief sun exposure on vitamin D levels in 20 young women for four weeks.
The study was conducted between October and November at latitude 37 degrees north, which is about the same latitude as Washington DC. Initial mean levels of Vitamin D were low: just 11 ng/ml, and no woman had levels greater than 20 ng/ml to begin the study. The women were told to get 20 minutes of midday sun exposure on their hands, forearms and face every weekday for four weeks.
Guess how much serum Vitamin D levels increased after a month of daily sun exposure? Nada. Vitamin D levels did not increase at all; in fact, they were a little lower than when the study began!
Why did it fail? Dr. Cannell thinks there are several possible reasons. Perhaps the women didn't comply as well as they reported. Perhaps the amount of UVB in mid-day sunlight in October and November at that lattitude is insufficient to make Vitamin D. Perhaps the area of the body exposed was not large enough to make Vitamin D. And finally, maybe the time of exposure wasn't long enough.
Dr. Cannell points out that human beings were originally equatorial animals. And living on the equator in primordial times, they didn't wear a whole lot clothes, and maybe not any. He estimates a Vitamin D input of 5,000 to 10,000 IUs per day for our primordial ancestors and an average blood level of 50 ng/ml.
I take 5,000 IUs of Vitamin D3 daily. It's the tiniest little capsule you can imagine, but it is a powerhouse of health support. And, I think that just about everybody ought to be doing it, although less for small children.