Dr. McDougall's Online Discussion Board

Jeff, are you aware of cases where people get what should by all accounts be sufficient sun exposure but they remain without adequate vitamin D levels, even for those with fair skin? Any thoughts on what can cause this, if not just genetics? I tried skimming and searching the Vitamin D Consensus thread and couldn't see anything, but might have missed a relevant article.

What’s your blood level?

JeffN wrote:What’s your blood level?

I'm asking for a friend whose ng/mL was consistently around 13 despite a lot of sun exposure for many months of tropic sun. No symptoms though, and no noticeable change in how they felt after supplementing. I figure without symptoms, no worries, unless there are silent effects that would wear them down over time.

Personally I'm fine, with end of summer at 65 and end of winter at 28 when I got tested. No issue.

I have to assume that if a large number of east asians test at lower vitamin D levels despite what should be far more than adequate sun exposure, if there are no symptoms, there must be some compensating mechanism that makes those levels just fine in such cases. But I'm not familiar with the studies so this is all assumptions on my part.

A quick search did turn this up though. If the mean value in China is 12.7 ng/mL (40.4 nmol/L), and the nation isn't absolutely plagued with rickets, there's something going on. Still though, Thailand whose people generally don't stay out of the sun as much had much higher values (mean value for women 22 ng/mL).
Vitamin D status and sun exposure in southeast Asia
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3897596

"The epidemic of obesity has added to the epidemic of vitamin D deficiency. Because vitamin D is fat-soluble, excess body fat will pull vitamin D out of circulation, thus contributing to lower levels."

Source: https://www.drmcdougall.com/misc/2015nl ... tamind.htm

"Mary [McDougall] is not an unusual example of well-sunned people failing this commonly prescribed test. Similar results were found during a study of active young people living in Hawaii with an average sun exposure of 29 hours a week. Even with all that vitamin D-promoting solar radiation, 51 percent of the group failed to meet sufficiency levels of 30 ng/mL.6 The highest reported level was 62 ng/mL and several people had values below 20 ng/mL. Another study of 495 women with an average age of 74 years, living in Hawaii, a geographical area with high environmental UV irradiance, found 44 percent of subjects had vitamin D values of less than 30 ng/mL, but none were below 10 ng/mL; and there was little evidence of seasonal variation of vitamin D levels.7"

"Based on recent reviews, adequate, I believe, is 20 ng/mL or greater (see below)..."

Source: https://www.drmcdougall.com/misc/2011nl/mar/vitd.htm

You Need Vitamin D to Live. How Could This Woman Survive With None in Her Blood?

"[T]he amount of free vitamin D that this woman received from her diet or exposure to sun may have been sufficient to develop her bones and keep them alive."

Source: https://web.archive.org/web/20200713072 ... bones.html