UV (Ultraviolet) Radiation, Vitamin D, Sunburns, and Skin Cancer

sunshineUltraviolet radiation comes in three separate wavelength groups:
  –UVA 320 – 400 nanometers 
  –UVB 281 – 289 nanometers
  –UVC 200 – 280 nanometers

UVB is the high-energy form of radiation that stimulates the production of vitamin D.  It is also the form of radiation that is absorbed by DNA and proteins, reddens skin, can cause sun burns and is the major contributor to non-melanoma skin cancers.  If it causes a sun burn, then it may also add to the risk of melanoma.

UVA contains much less energy than UVB. Up to 100 times the amount of UVA reaches the earths surface, compared to UVB and it is able to penetrate deeper into the layers of your skin where it can increase free radicals causing wrinkles, and increased chances of melanomas, the most deadly type of skin cancer. UVA also affects the melanocytes (your pigment cells) more, and can affect the immune system.

Without sunscreens, people would not be able to stay out in the sun long enough to put themselves at much risk for melanoma.  The older sunscreens just blocked UVB so people would not burn, however this lead to people being able to spend very long hours in the sun accumulating much more UVA radiation than was safe, and increasing the risk of melanomas.  Fortunately, most sunscreens are now full spectrum sunscreens that protect against most UVA and nearly all the UVB if SPF numbers are high enough.  SPF 8 protects against 90% of the UVB and SPF 30 about 99%.

Think of A for aging and B for Burning.  It is also the UVB that we need to start the reaction in the skin that converts 7-dehydroxycholesterol to vitamin  D3.  Once this is in the blood stream it has a half life of up to 2 weeks, and is converted to active 25-OH D3 in the liver.  In the kidneys this is converted to the biologically active 1,25-OH D3 as needed for the body. 

The issue of cancers and vitamin D is an interesting one. Since World War II, it was discovered that the further north a man lived, the greater their chance of prostate cancer.  This relationship has been confirmed beyond a doubt.  The higher your latitude (and thus the lower your vitamin D), the higher your chance of dying from prostate cancer. Read More Here.   

This relationship has been confirmed for breast cancer and colon cancer also. More… Given that breast cancer kills 40,000 women a year in the US alone, and about 500 die from non-melanoma skin cancers (the type likely resulting from UVB exposure) if you were to balance your risk factors, it seems only logical that some careful limited sun exposure (not enough to burn you or even cause significant redness of the skin at 24 hours) would make total sense.  Can I say common sense?  Common sense is lost in narrowly defined research, and is definitely out the window when big money and conflicts of interest get involved. The sun screen and sun lotion industry has done a masterful job of studying and documenting the ill effects of the sun to the point that most of us have sun phobia and dermatologists have been swept up in the fear. We have lost the forest for the trees, or is it the sun we have lost?

So the moral of this story is that you should take enough vitamin D3 to keep your circulating levels in the optimal range (50-80) and consider just enough sun exposure to avoid any redness, but you’ll need for that exposure to be without the UVB blocking sun screens.  Just 15 minutes or less a week would be enough for most if you already had enough vitamin D on board.  

Dr. Paul


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