Vitamin D Newsletter


Sunlight and Melanoma

Anonymous writes:

Dr. Cannell: My dermatologist told me that the sun causes melanoma and I should stay out of the sun. He seems to know what he is talking about.

Dr. Cannell replies:

Sunlight contains radiation. Radiation can both help and harm you. The body figured that out long ago, way before dermatologists evolved. People who lived in the sun, like your ancestors in Africa, did not get sunburned. They were in the sun most of the day so their skin developed a natural sunscreen, melanin, which pigmented their skin black or brown. That pigmentation rapidly disappeared in the humans that migrated to temperate latitudes beginning 50,000 years ago. Today, most light skin people also deposit melanin in their skin on sun exposure; we call it a tan and it has always been a sign of good health. Diets rich in vegetables, fruits, and omega-3 fats—and the absence of appreciable quantities of omega-6 and trans-fats—also protects your skin from burning. The people who get sunburned are modern humans who live and work indoors, avoid fruit and vegetables, love french fries and chips, hate salmon, and go to the beach two or three times in the summer to roast themselves. Frequent sunburns, especially in childhood, are but one factor in melanoma—genetics and diet are more important.

There is a dermatologist at Rush University Medical Center, Dr. Arthur Rhodes, who understands most of this. If you want to read a reasonable dermatologist, one who has escaped the mass hysteria that all melanomas are caused by sunlight, read his paper on cutaneous melanoma.

An even better discussion is Oliver Gillie's recent paper: A new government policy is needed for sunlight and vitamin D.

The real question is, "Which is best: vitamin D supplements or sun exposure?" The answer is tough. First, the sun won't make much vitamin D during the winter at temperate latitudes above 37 degrees, so if you rely solely on the sun, you'll need to take supplemental vitamin D, use a UVB lamp or a sunbed during the winter. Second, African Americans can't spend an hour in the sun every day so they must take adequate supplements. Third, what other good does the sun do in addition to making vitamin D? The last one is the clincher for me and was recently discussed by Luca and Posonby in the paper below. As humans evolved in the sun, I sensibly go in the sun when I can (without drinking a bottle of Coppertone chased with a bottle of Deepwoods Off).

If you are scientific, try a little experiment. Take someone you know with fair skin who burns easily and who doesn't go in the sun. Take him or her into a sun tan booth and find out exactly how many minutes it takes for their skin to just begin to turn pink, called one minimal erythemal dose  (MED). Then, keep them out of the sun but give them 10,000 units of vitamin D a day for a month. Then take them into the sun tan booth again and see how long it takes for them to get one MED. What you will discover is that their time for one MED is longer. High vitamin D blood levels help prevent burning and facilitate tanning. My teenage daughter, who used to burn easily, discovered this. Against my advice, she took 5,000 units of vitamin D every day and regularly went into a sun tan booth as well. Now all her friends are begging her to tell them why she never burned and got so incredibly tan, tanner than she ever got before. Furthermore, burning in vitamin D deficient people actually may have an evolutionary benefit. Burning heats the skin and the final step in the production of vitamin D is driven by high skin temperatures. It also makes evolutionary and physiological sense that high vitamin D blood levels would facilitate rapid tanning and thus protect against vitamin D toxicity. Just remember, burning is dangerous and should always be avoided.

Page last edited: 17 August 2010