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Old 11-07-2017, 04:44 AM   #89
R.B.
Senior Member
 
Join Date: Mar 2006
Posts: 1,843
Re: Vitamin D thread -Please use this for your Vit D info.

Hi Laurel

Thank you for making me laugh. Indeed there is much confusion and differing of opinion. The Holick and Grass Roots videos (see previous pages) are worth watching if you have not done so - Professor Holick has his own particular tongue in cheek view on the restricted wider health outlook of dermatologist as he would see it. https://www.youtube.com/watch?v=hiGBVDcbFVk

You will note that UVB only reaches the earths surface in significant amount in the center of the day in more northern latitudes. Thus getting sun exposure at the beginning and end of day in these latitudes may simply mean you get UVA exposure with little UVB (so very low capacity to make vitamin D and that is before the application of moisturizer that often contains UVB blockers.)

UVB comprises 5-10%, and UVA the balance of UV, 90-95% that can reach the earths surface. UVA penetrates deeper in the skin damaging DNA and enzymes, and papers suggest is probably equally capable of factoring in cancers as UVB.

UVB promotes vitamin D precursor production. Vitamin D is put back in the skin as an antioxidant so protective.

Skin product producers have begun to talk about acknowledge the role of UVA in cancer now there are UVA blockers in the market, but blocking UVA is not as easy as blocking UVB.

The face apparently (I have not read any papers on this) produced less vitamin D than other skin, and gets more exposure, so logically would be a good area to protect whilst allowing non-burning sun exposure of other areas, but it needs to contain a UVA blocker too - and then there are the wider issues as to chemicals etc etc.

Things get even more complicated because of the siloed nature of skin cancer / suncream research - they just focus cancer rates and sun creams

But the increase in skin cancers could also be, and likely is also due to other dietary factors; lack of important nutrients in the diet, but nobody ever talks about that. For example to pick one nutrient we tend to get too much of, mice on a low Omega 6 diet required double exposure and were more resistant to skin cancer.

It could even be that risk was increased by historic use of UVB only blocking creams, and the consequent over exposure to sun as the burning messaging to get out of the sun was blocked, with consequent excess UVA exposure leading to increased risk of cancer initiation. Consistent with this builders and farmers, not know for rigorous sun cream application, have been noted to possibly have lower comparative skin cancer rates (limited research).

Further Vitamin D does so many things; low vitamin D is associated with a whole range of other health risks. Visit this site, pick your condition and scan the research paper summaries - https://www.vitamindwiki.com/VitaminDWiki

The Swedish study linked below neatly sums things up concluding that your risk of melanoma may be reduced if you avoid the sun, but your risk of dying early of other things is increased.

Avoidance of sun exposure is a risk factor for all-cause mortality: results from the Melanoma in Southern Sweden cohort.

https://www.ncbi.nlm.nih.gov/pubmed/24697969

The results of this study provide observational evidence that avoiding sun exposure is a risk factor for all-cause mortality. Following sun exposure advice that is very restrictive in countries with low solar intensity might in fact be harmful to women's health.

Medscape commented on the paper with the headline


Avoiding Sun as Dangerous as Smoking


https://www.medscape.com/viewarticle/860805

They are now beginning to make creams that block UVA but not the bits of UVB that make vitamin D.!

New Approach to Develop Optimized Sunscreens that Enable Cutaneous Vitamin D Formation with Minimal Erythema Risk
http://journals.plos.org/plosone/art...l.pone.0145509

Last edited by R.B.; 11-07-2017 at 05:00 AM..
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