It’s summertime and I have sunshine on the brain (pretty hard not to at 111 degrees!)
Sunshine and thinking people have a “complicated relationship.” First, it is undeniably the giver of life. Without sunshine, Planet Earth would be close to absolute zero. Even the gases would be solid.
There would be no life at all, unless crystal growth counts. Yet this life-giving radiation is a source of wrinkles, aging, and the occasional cancer. Icarus syndrome, perhaps.
A suntan is the most visible effect of time spent in the sun. The ability to suntan is, like so many other things in life, fundamentally unfair (blame it on your parents). Melanin is the stuff of suntans. It is pigment made by your skin cells in response to ultraviolet radiation. It protects your skin cells from genetic damage.
The amount of melanin you start with is hereditary. If your people hail from Ireland, you have so little melanin that you can sunburn just thinking about a sunny day. If your blood calls Persia home, beach volleyball is your friend.
Suntans have not always been popular. As recently as a couple of generations ago, a suntan was considered evidence of an outdoor career, i.e. farm labor.
People went to extremes to appear pale; not only avoiding sun exposure, but applying somewhat poisonous bleaching chemicals to their skin.
Fast forward to the ‘70s and suntans are back in fashion. The “California look;” all blond and suntanned, seizes the public consciousness. Rickets almost disappears; and unemployed doctors go into dermatology.
Sunblock was invented in response to all this healthy glow; our schizophrenic thing with sun again. And someone decided to dice up the ultraviolet spectrum, forever confusing even smart people. Truth in advertising, SPF reform, hasn’t caught up with the sunblock industry yet, although the FDA is threatening. Smear this on and take 20 years off your skin.
Sunshine is made of infrared, visible and a couple hundred wavelengths of ultraviolet radiation. Infrared keeps you warm and cozy, like a lizard on a sunny rock. Visible light makes things look good, avoids broken legs, and gives you an excuse to wear cool sunglasses. Ultraviolet radiation is the pesky part. It is higher energy radiation and can breakdown the DNA in your skin, which keeps dermatologists employed.
When we talk ultraviolet radiation (UV), we are mostly talking about UVB (280-320 nm). UVB is blocked by the ozone layer and sunblock (mostly). It will give you a bad sunburn, and perhaps worse – old, saggy, wrinkled skin, age spots or cancer.
But UVB also stimulates vitamin D production; which is a free radical scavenger with anti-cancer properties. It also stimulates melanin production, which is the ultimate sunblock.
UVA is the latest thing. It is a little higher frequency than B (UVA 320-400nm). It comes down on us all daylight hours in all seasons. It is not blocked by the ozone layer or by most sunblocks. UVA oxidizes melanin which darkens it, gives you some quick color, but no sunburn protection. Oxidized melanin doesn’t stop UV anything. You need more melanin, not just a different color of melanin. UVA doesn’t directly damage DNA – it creates free radicals, which may be worse.
There is a great deal of research being done on new sunblocks effective against both UVA and UVB. Living in the desert we have learned to live in peace with the sun. Sunblocks, shade, Gatorade and cool sunglasses are a part of our lives. I draw the line at funny little sun umbrellas, not until I’m much older.
As always, take care.
Dr. B
