Okay, maybe not lies, but there is certainly a lot of misinformation out there about how to get your Vitamin D from the sun.
A reader’s comment on my previous post about Vitamin D:
daniel horton– I was expecting to read an article about getting outside and absorbing some rays based on the photo but then you only wrote about supplements. Sad. 🙁
Yes, I agree it’s sad and I fully intended to include information about getting out in the sun to get your Vitamin D in my last post, but when I did the research, I found out that there’s a lot more to it than I realized. Too much to fit it all into the first post.
So, the rest of this is for our friend, Daniel. 😉
What do the following statements all have in common?
- In Chicago, you can’t produce Vitamin D from the sun until March 25, and by September 16, it is too late.
- Office workers get 3-9 times less sun exposure than outdoor workers, yet the indoor workers’ risk of getting malignant melanoma is on the rise, while outdoor workers’ risk has remained steady.
- U.S. drivers are more likely to develop skin cancer on their left arm.
- Some sunscreens actually increase your risk for skin cancer.
Give up?
All of these statements have to do with the fact that the sun emits different types of ultra-violet rays and they each have very different properties.Two types of rays are UVA and UVB rays. Both of them, when taken in excessive amounts, can contribute to skin cancer, but UVB rays cause sunburn more readily than UVA rays. However, you produce Vitamin D in your body only from the UVB rays.
The second important fact is that UVA rays have a longer wave length, so they penetrate the atmosphere more easily. They can penetrate in areas where the the latitude is too high for UVB rays to penetrate and they can penetrate through smog, cloud and window glass when UVB rays can’t. The sun has to be at least 50 degrees above the horizon for UVB rays to reach the earth. Here’s a fun website where you can calculate the date that happens in your hometown.
So, if you put those two pieces of information together, you can come up with the best strategy for maximizing your Vitamin D production from the sun, while minimizing your skin cancer risk.
How to do this? Well, your goal is to get just enough UVB rays to produce optimal amounts of Vitamin D in the shortest amount of time. When is the best time to do this? As it turns out …. noon. Surprising, isn’t it? Here’s the deal. At noon, the shorter, Vitamin D-producing, UVB rays have their best chance of reaching the earth unscattered. Thus, you can produce more Vitamin D in a shorter amount of time at noon than any other time of the day. This limits the total amount of time your skin is exposed to cancer-causing rays.
Here’s a U.S. map that shows the possibility for Vitamin D production in February.
Exactly how much time do you need to spend in the sun to produce adequate Vitamin D? It depends. And it actually depends on quite a few variables … the latitude and elevation of your home town, how old you are, how skinny you are, how healthy you are, how dark your skin is and whether you’re standing up or lying down. Yeah. It’s complicated.
However, for fair-skinned people, 10-15 minutes a day at noon in the summer, wearing no sunscreen and a minimal amount of clothing should be enough to do it. Do this several days a week for optimal health benefits.
What about tanning beds, can you produce Vitamin D when you use a tanning bed? Typically not, as most tanning spas calibrate their beds to include about 95% UVA rays because those are the rays that produce the bronze suntan so desired by their customers. However, the UVA rays aren’t going to allow you to produce Vitamin D, so tanning beds aren’t the answer for most people.
Oh, and why do some sunscreens actually increase your risk for skin cancer? Because many sunscreens only contain protection from UVB rays, preventing sunburn, but allowing UVA rays full access to your skin. While UVA rays are less likely to burn you, they still cause the skin damage that can lead to cancer. In fact, because you are not getting a sunburn when you use UVB protection sunscreen, you typically stay out in the sun longer, thus actually increasing your exposure to the cancer-causing UVA rays.
In addition, Vitamin D actually helps prevent certain skin cancers, so by minimizing the Vitamin D-producing UVB rays, while increasing the cancer-causing UVA rays, you get a double whammy when using sunscreen that contains only UVB protection. Look for a sunscreen that protects from both UVA and UVB rays.
This phenomenon also holds true for both office workers and automobile drivers. The UVA rays penetrate through glass windows, increasing the risk for skin cancer, at the same time that the shorter UVB rays are stopped by the glass, eliminating the production of Vitamin D and its cancer-fighting properties.
Best strategy for Vitamin D production and avoiding skin cancer at the same time?
Short, consistent time in the summer noonday sun without sunscreen. The rest of the time, use a sunscreen that screens both UVA and UVB rays. Supplement during those times of the year when the sun is below 50 degrees from the horizon.
Happy sunning. 🙂
