Ideal Time For Sun Exposure

[ilikecats]

does anyone know what time or day ray peat thinks is ideal to get out in the sun? In terms of achieving maximum benefits from your sun exposure?

 

[loess]

Supposedly UVB rays (which are the UV rays that, when they hit the epidermis layer of the skin, instigate the process of the production vitamin D) are only available when the angle of the sun along the horizon is greater than 50 degrees. Another term for this is the sun's azimuth. You can use this table and input your location to see the times of day when the angle is greater than 50 degrees: Sun or Moon Altitude/Azimuth Table

Chris Masterjohn wrote an article a while back questioning the latitude hypothesis:
http://www.westonaprice.org/our-blogs/cmasterjohn/vitamin-d-problems-with-the-latitude-hypothesis

In any case, one probably casts the widest net for vitamin D synthesis at times when the sun azimuth is > 50 degrees.

 

[raypeatclips]

The ideal time for sun exposure is at night when it is dark.

 

[Rafe]

He's right, you know.

 

[encerent]

Early morning and near sundown there is less harmful blue to violet and ultraviolet light. Most of the light at these times are orange to red to infrared.

 

[biggirlkisss]

i would think when its brightest 1 to 4 pm.

 

[Brian]

My preference for a short full body sunbathe is near noon, but only for 5 to 10 minutes per side for a full spectrum exposure. Otherwise I prefer early morning and evening light for longer skin contact during the summer.

But I also like being outdoors as much as possible on days that I can but out of direct sun contact more than is comfortable. Mostly for the bright environment that is hard to replicate indoors.

 

[dd99]

I think it depends what you're looking for.

To get the benefits of red light, you need exposure to early morning or late afternoon sunlight.

To make vitamin D, you need to go out when there is UVB available, which is usually between around 10am and 3pm, but varies throughout the year.

To expand on what loess wrote above, your body synthesises vitamin D from UVB, and UVB only enters the atmosphere when the sun is more than 30 degrees above the horizon (there has been some discussion amongst experts about this figure, but they seem to be settling on 30 degrees). That means if you live more than around 35 degrees from the equator, you won't be able to make vitamin D for some times of the year, because the sun simply won't be at a steep enough angle relative to your position for UVB to reach you.

For example, I live in London (51 degrees north of the equator), and the last day this year that the sun is more than 30 degrees above the horizon is 13 October. After that, I won't be able to create vitamin D until 26 February 2017.

I couldn't find anything like the below online, but I think the chart that I made (from my dilettante understanding of all this) shows the roughly optimal times to go outside: when you still have red light, but are starting to get some UVB - so in the mid morning and mid to late afternoon, depending on sunrise and sunset and UVB times. Try the dminder app for precise times where you are.

Personally, I try to get some light around 10am and again around 3pm - and if there is the possibility of making some vitamin D (i.e. between end February and mid October for me), I will get 5 or 10 minutes of sun at solar noon (right now, 12:45 - fluctuates from 11:45 to 12:15, but you need to factor in daylight savings).

 

[GelatinGoblin]

Good thread

 

[Mauritio]

"In view of this, short, nonerythemogenic exposures around noon should be recommended rather than longer nonerythemogenic exposures in the afternoon. This would give a maximal yield of vitamin D at a minimal CMM risk."

At what time should one go out in the sun? - PubMed

To get an optimal vitamin D supplement from the sun at a minimal risk of getting cutaneous malignant melanoma (CMM), the best time of sun exposure is noon. Thus, common health recommendations given by authorities in many countries, that sun exposure should be avoided for three to five hours...

pubmed.ncbi.nlm.nih.gov

 

[Lejeboca]

"In view of this, short, nonerythemogenic exposures around noon should be recommended rather than longer nonerythemogenic exposures in the afternoon. This would give a maximal yield of vitamin D at a minimal CMM risk."

Thanks for the find. Very interesting. And it seems to corroborate with Ray's saying that, given low moderate exposure, higher-level radiation passes faster through our bodies w/o much damage contrary to the effects of lower-level radiation that tends to be less scattered in the atmosphere and to 'linger' in our bodies.
From the said paper ( At what time should one go out in the sun? - PubMed ) :

"Since ultraviolet B (UVB, 280-320 nm) is much more scattered in the atmosphere than ultraviolet A (UVA, 320-400 nm) is and has widely different
health consequences, the choice of geometric representation for the human body is of fundamental importance. "

"With the cylinder model, high UVA fluence rates last about twice as long after noon as high UVB fluence rates do"

Spoiler: Figure for Conclusion that postponing moderate non erythemogenic sun exposures from noon to afternoon yields less vitamin D at a similar melanoma risk.

 

[laleto12]

use dminder app guys on your smartphones. It tells you a lot about sun abd vitamin d

 

[Lejeboca]

A a detailed web tool to find out UVB vitamin D equivalent to ~1000IU (25 mcg) orally based on your geographical, atmospheric, skin type, and time of the day parameters.
Calculated Ultraviolet Exposure Levels for a Healthy Vitamin D Status - simple version

N.B. They use Hollick's rule: "sun exposure 1/4 of a minimal erythemal dose (MED) over 1/4 of a body is equivalent to 1000 International Units (IU) oral vitamin D3." (see the references in the link above.)

 

[sunny]

Short exposure to uvb for making D at noon, solar noon (D Minder app). As much sunlight at dawn until uvb comes (which is about 9am currently), and then evening sun as much as possible. The infrared that is pre and post uvb are good for the body and for getting enough bright natural light in your life.