General Question

emilyrose's avatar

Do our bodies absorb vitamin D from the sun even if we are in the shade?

Asked by emilyrose (2253 points ) October 23rd, 2008

I have been hearing a lot about vitamin D deficiency. Obviously it’s not great to sit in the sun all day. Can we still get vitamin D from the sun without getting a sunburn?

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8 Answers

La_chica_gomela's avatar

I don’t think you can absorb sufficient vitamin D in the shade, but you can do it without getting a sunburn.

Direct sun exposure to your arms and legs for five to 10 minutes daily is sufficient for proper vitamin D production.
-Quote from the Mayo Clinic

I have very fair translucent skin, and even in the brightest sun it takes at least about 15 minutes for me to burn.

Also, if you don’t want to expose your skin to direct sunlight at all, you can still get the recommendation for vitamin D by eating “foods that are naturally rich in vitamin D, including oily fish (salmon, mackerel, sardines) and egg yolks, [and] foods that are fortified with vitamin D, such as cereal, bread, milk and yogurt” or taking vitamin supplements.

[same link; you might want to read it for more info about vitamin D]

laureth's avatar

Vitamin D is formed when sunlight hits the skin and reacts with your own natural 7-dehydrocholesterol (yes, I looked that up, heh). If light doesn’t contact it, no D forms, which is why it’s harder to get this vitamin during the winter, say, when we’re more likely to wear long sleeves or stay indoors.

I’m guessing you mean “light shade,” as opposed to the kind of shade that occurs indoors or under clothes. It would seem that you make D in the skin where sunlight reaches, so if any is made in shade, it is probably insubstantial.

I’m not a doctor or medical professional, though. Just sayin’.

Magnus's avatar

I’ll answer your question with a question. How can you be exposed to the sun in the shade?

La_chica_gomela's avatar

Magnus, if there was no sunlight in the shade, how could you see anything?

hoosier_banana's avatar

The key to vitamin D production is UVB waves. They are the mid-sized UV light beams and do not pass through window glass, but are still in the “shade”. Found this;

“When people in the shade estimate UVB exposure based on an eyeball assessment, they’re getting about twice as much UVB as they think,” Grant says. UVB, unlike visible light, doesn’t shine down in a straight line from the sun. It bounces around in the atmosphere.”

“How much UVB you’re getting more closely correlates with how much sky you can see,” Grant says. “If lots of the sky is obstructed, you’re getting a lot less UVB.”

La_chica_gomela's avatar

Banana, can you please give us a source?

Because I was under the impression that UVB caused cancer.

From what I read on the Mayo Clinic website, it sounded like vitamin D was produced in the presence of visible sunlight, not ultraviolet, but I could be wrong.

Please share a link with us, so we can all check it out!

Or maybe Shilolo will come along and just tell us the deal!

hoosier_banana's avatar

Sure, I just looked at wikipedia’s uv page. Here is the link to the article about uv in the shade. If you think about it, UV is a natural part of our world, and our species evolved to use it, so cutting it out can be just as bad as overdoing it, both cause cancer.

shilolo's avatar

Well, I have to go crack open my old biochemistry book, but from memory, I would say that UV (and not visible) light is the force behind the production of Vitamin D. That said, as little at 10 minute per day in the sun is sufficient to maintain adequate vitamin D levels, and in any event, so many things are fortified these days, it can be very hard to become deficient.

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