7

votes

Vitamin D from indirect sunlight?

Answered on August 08, 2017
Created July 07, 2012 at 2:43 PM

Can you get vitamin D from being outside (in relative shade?) with indirect sunlight?

I am sure it would be a fraction of direct sunlight exposure, but I was wondering if there was any significant vitamin d we can get from indirect sunlight.

01114547678b001f3e52cc3a9d343fd1

(-23)

on August 02, 2014
at 08:59 PM

Interesting that no one before upvoted this spectacular answer.

03a4ec34751186201a56da298ac843ce

(4100)

on July 21, 2012
at 04:33 AM

Take off your shirt.....lol...good suggestion for the ladies!

8e3782b68e033763485472f414f507a5

(2433)

on July 07, 2012
at 09:02 PM

UVA is not equally present from dawn to dusk. Trust me, I've measured it. It gets more intense as the sun rises just like UVB. (In my measurements the ratio of UVA:UVB varied based on time of day and time of year -- ranging from 15:1 (summer, high sun) to 30:1 (winter, as well as low sun)).

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5 Answers

8
21fd060d0796fdb8a4a990441e08eae7

(24543)

on July 07, 2012
at 03:06 PM

Not much, unfortunately.

If the UV index outside is let's say at 5, then the UV index in shade will be...lower (I don't recall how much lower, but it's much lower).

Combine that with the decreased per-unit of skin area production of vitamin D in non-torso areas (meaning face and arms, areas that are typically exposed for the working professional) and you get not much vitamin D production. For optimum vitamin D, take your shirt off and run around the streets :)

There is glass that lets in UVB, which I guess would let you produce vitamin D indoors to some degree, but it's hella expensive. http://www.dendroboard.com/forum/parts-construction/33431-uvb-uva-penetrate-glass.html

03a4ec34751186201a56da298ac843ce

(4100)

on July 21, 2012
at 04:33 AM

Take off your shirt.....lol...good suggestion for the ladies!

2
Cb9a270955e2c277a02c4a4b5dad10b5

(10989)

on March 05, 2016
at 04:05 PM

Yes, you may get around 50% of the vitamin d production in certain shaded areas as you would in full sun: http://www.ncbi.nlm.nih.gov/m/pubmed/16005208/ .

0
Bfc4652ed95fa33a3de1fbe1424b756c

on August 08, 2017
at 09:26 AM

I'm no expert but I believe you can hit your RDA if you stay long enough in that shade as long as you're outside and in direct exposure to some sunlight (light cracks through leaves).

From what I understand of it, the amount of uvb you receive depends on many factors: amount of skin area exposure, skin type (lighter skin is easier), time of day, location (equator is faster), climate (clouds, pollution, etc.), duration, and season.

0
2ab23de741113eb0d7a74bd343d29381

on March 05, 2016
at 06:04 PM

Not ony is there almost no efective UVB radiation from reflected sunlight, vitamin D (hormone) production is almost exclusively achived between the hours of 10 am and 3 pm, the exact time dermatologists tell us to stay out of ther sun. you actually need exposure of your torso and legs to be able to make an appropriater amount of D on your skin without burning, unless you have a good base tan. sunscreen and just having your face or arms exposed wont do much. 

Cb9a270955e2c277a02c4a4b5dad10b5

(10989)

on March 05, 2016
at 06:24 PM

Joel, what do you mean by "there is no effective UVB radiation from reflected sunlight"? Does something happen to 100% of the UVB radiation when it deflects off a tree limb, deck, sand, wall that changes the wavelength? UVB rays bounce off millions of particles in the atmosphere before they reach an individual.

0
Da12b342d4959f5bd776c0f00b072a6c

on July 07, 2012
at 07:27 PM

Basically, no. All sunlight is not the same. Of the two main types of UV rays, UVA - which is equally present from dawn to dusk in both summer and winter and UVB radiation – which is the only form of sunlight that produces Vitamin D and varies in strength depending on the height of the sun. The ‘higher’ the sun, the greater the UVB. Getting some regular exposure around mid-day, but avoiding overexposure is the key. Commonly heard advice to get our sun exposure in either the early morning or late afternoon may greatly compromise our health. Regular UVA radiation -without UVB - can alter the immune system and increase risk for skin cancer. Glass filters UVB. UVA can pass through windows and break down vitamin D.

8e3782b68e033763485472f414f507a5

(2433)

on July 07, 2012
at 09:02 PM

UVA is not equally present from dawn to dusk. Trust me, I've measured it. It gets more intense as the sun rises just like UVB. (In my measurements the ratio of UVA:UVB varied based on time of day and time of year -- ranging from 15:1 (summer, high sun) to 30:1 (winter, as well as low sun)).

01114547678b001f3e52cc3a9d343fd1

(-23)

on August 02, 2014
at 08:59 PM

Interesting that no one before upvoted this spectacular answer.

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