I don't know if it would be worse to never have a big song or to think you have it "made in the shade" and then never walk on sunshine again. (Hmmm, sounds like my struggle to become nationally known in medicine. I'll let you know in 30 years.)

I love sunshine, but I also wear sunscreen because our ozone layer looks like Britney Spears' clothes: too much exposure. So should Katrina re-write her song, "I'm walking on sunshine, Wooah, and don't it give me vitamin D? Hey! Alright now!"? (Where is Clive Davis? I want to sign a record deal. Pronto!)

Dr. Connie Christ, a fabulous nephrologist in Charlottesville, gave me the latest New England Journal of Medicine article on vitamin D deficiency because she sees it all the time in her practice, as do I. Vitamin D deficiency (or insufficiency) might be affecting up to 1 billion people in the world. (I wish Carl Sagan were still here to say billions and billions.) Why?

Sunlight is the most effective way to get vitamin D but also is the most effective way to get skin cancer. So we're avoiding the sun and using more sunscreen to block out UVB, but UVB radiation exposure to the skin causes 7-dehydrocholesterol to convert into previtamin D3, which a long way down the line converts to vitamin D. (See? T his is where bureaucracy originated. Nothing in the endocrine system is a simple, one-step task.)

Vitamin D is important for calcium and phosphorus absorption by the gut so that healthy bones can be made. Vitamin D is also important to keep PTH (parathyroid hormone) levels from becoming high, which can lead to thinner bones.

Yet half of women being treated for osteoporosis are thought to be vitamin D deficient, and nearly half of Americans are probably low on vitamin D or deficient during the winter months. Of course, in the Middle East where women wear burkas, they have more vitamin D deficiency due to lack of sunlight on the skin. 

So what about foods with Vitamin D? Well, Alaskans should be in good shape because fresh wild fish, in particular wild salmon, have a lot of vitamin D. 

Studies show adults who get less than 400IU of vitamin D have more problems, including osteoporosis, fractures, muscle and joint pains (and possibly even Type II diabetes, poor immune systems, mental illness, and cancer-- though the associations aren't really that high). Vitamin D 800-1000IU in those who don't get UVB-radiated light seems to be beneficial, and 3.5 ounces of wild fresh salmon has about 1000IU of vitamin D.

Remember on The Waltons when Mary Ellen tried to give cod liver oil to two orphans with rickets? Well, cod liver oil and other fish have quite a bit of vitamin D. Most dairy is fortified with 100IU vitamin D like 8 ounces of milk or yogurt, and 3 ounces of cheese. 

For patients who need vitamin D, there are prescription-strength doses of vitamin D2 or D3 which can help boost levels. Vitamin D toxicity is pretty rare, but in general a blood level of 25-OH vitamin D is too high. 

It's so sad Mr. Ozone is disappearing like characters on the TV show Lost. Sitting out in the sun isn't the same anymore. I wonder if all of us are going to have to wear burkas to prevent skin cancer-- but then our vitamin D levels might be in peril.

Perhaps it will come to a point there will be a beauty pageant for women in burkas. Would the winner be Delta Burka?

Dr. Hook cracks a joke or two, but he's a renowned physician with a local practice. Email him with your questions.

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