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Wednesday, November 6, 2013

Vitamin D production from UV radiation: The effects of total cholesterol and skin pigmentation

Our entire body naturally produces as significantly as ten,000 IU of vitamin D based on a few minutes of sun exposure when the solar is substantial. Getting that significantly vitamin D from nutritional sources is very tough, even right after “fortification”.

The earlier mentioned refers to pre-sunburn exposure. Sunburn is not associated with increased vitamin D generation it is linked with skin injury and cancer.

Solar ultraviolet (UV) radiation is generally divided into two primary varieties: UVB (wavelength: 280–320 nm) and UVA (320–400 nm). Vitamin D is made primarily primarily based on UVB radiation. Nevertheless, UVA is significantly more abundant, amounting to about ninety percent of the sun’s UV radiation.

UVA looks to cause the most pores and skin injury, despite the fact that there is some discussion on this. If this is correct, one would anticipate pores and skin pigmentation to be our body’s defense primarily against UVA radiation, not UVB radiation. If so, one’s ability to produce vitamin D primarily based on UVB ought to not go down drastically as one’s skin becomes darker.

Also, vitamin D and cholesterol seem to be to be closely joined. Some argue that a single is produced primarily based on the other other folks that they have the same precursor substance(s). No matter what the scenario might be, if vitamin D and cholesterol are certainly carefully linked, one would count on reduced cholesterol stages to be associated with lower vitamin D creation primarily based on daylight.

Bogh et al. (2010) not too long ago released a very exciting research. The url to the research was presented by Ted Hutchinson in the responses sections of a previous post on vitamin D. (Many thanks Ted!) The research was released in a refereed journal with a reliable popularity, the Journal of Investigative Dermatology.

The study by Bogh et al. (2010) is notably fascinating due to the fact it investigates a handful of concerns on which there is a good deal of speculation. Between the troubles investigated are the consequences of whole cholesterol and skin pigmentation on the generation of vitamin D from UVB radiation.

The determine beneath depicts the connection in between whole cholesterol and vitamin D generation primarily based on UVB radiation. Vitamin D generation is referred to as “delta twenty five(OH)D”. The univariate correlation is a pretty higher and significant .fifty one.


25(OH)D is the abbreviation for calcidiol, a prehormone that is made in the liver primarily based on vitamin D3 (cholecalciferol), and then transformed in the kidneys into calcitriol, which is normally abbreviated as one,twenty five-(OH)2D3. The latter is the energetic form of vitamin D.

The table beneath shows nine columns the most relevant types are the very last pair at the correct. They are the delta twenty five(OH)D levels for folks with dark and honest pores and skin right after exposure to the same sum of UVB radiation. The big difference in vitamin D creation in between the two teams is statistically indistinguishable from zero.


So there you have it. In accordance to this review, lower complete cholesterol would seem to be associated with impaired capability to make vitamin D from UVB radiation. And skin pigmentation seems to have little  effect on the quantity of vitamin D made.

I hope that there will be far more analysis in the future investigating this study’s promises, as the study has a handful of weaknesses. For case in point, if you just take a search at the 2nd pair of columns from the proper on the desk previously mentioned, you will notice that the baseline twenty five(OH)D is lower for men and women with darkish skin. The variation was just limited of currently being important at the .05 level.

What is the problem with that? Well, a single of the results of the study was that decrease baseline twenty five(OH)D levels were substantially related with larger delta twenty five(OH)D stages. Still, the baseline distinction does not appear to be big enough to totally make clear the lack of distinction in delta twenty five(OH)D ranges for folks with dark and fair skin.

A broadly cited dermatology researcher, Antony Young, published an invited commentary on this examine in the exact same journal problem (Young, 2010). The commentary factors out some weaknesses in the research, but is generally favorable. The weaknesses include the use of small sub-samples.

References

Bogh, M.K.B., Schmedes, A.V., Philipsen, P.A., Thieden, E., & Wulf, H.C. (2010). Vitamin D creation following UVB exposure depends on baseline vitamin D and complete cholesterol but not on skin pigmentation. Journal of Investigative Dermatology, a hundred thirty(two), 546–553.

Young, A.R. (2010). Some light on the photobiology of vitamin D. Journal of Investigative Dermatology, one hundred thirty(2), 346–348.
Title: Vitamin D production from UV radiation: The effects of total cholesterol and skin pigmentation
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