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How many minutes of sun do I need – age, skin color, UV index – Nov 2014

Minimum Exposure Limits and Measured Relationships Between the Vitamin D, Erythema and International Commission on Non-Ionizing Radiation Protection Solar Ultraviolet

Photochemistry and Photobiology. DOI: 10.1111/php.12394
Nathan Downs 1,2,3,*, Alfio Parisi 1,3, Harry Butler 1,3, Joanna Turner 1,3 and Lisa Wainwright

The International Commission on Non-Ionizing Radiation Protection (ICNIRP) has established guidelines for exposure to ultraviolet radiation in outdoor occupational settings.
Spectrally weighted ICNIRP ultraviolet exposures received by the skin or eye in an 8 hr period are limited to 30 Jm−2.
In this study, the time required to reach the ICNIRP exposure limit was measured daily in ten minute intervals upon a horizontal plane at a subtropical Australian latitude over a full year and compared with the effective Vitamin D dose received to ¼ of the available skin surface area for all six Fitzpatrick skin types. The comparison of measured solar ultraviolet exposures for the full range of sky conditions in the 2009 measurement period, including a major September continental dust event, show a clear relationship between the weighted ICNIRP and the effective vitamin D dose. Our results show that the horizontal plane ICNIRP ultraviolet exposure may be used under these conditions to provide minimum guidelines for the healthy moderation of vitamin D, scalable to each of the six Fitzpatrick skin types.

Publisher rents PDF for $6

VitaminDWiki rented the PDF and extracted the following

Skin type 1 (Whitest) lying down (Full body?)
UV index (3-6) 9,400 IU in 19 minutes
UV Index ( <3) 10,300 IU in 73 minutes

Need more sun as you get older
Need 17% more for age 22-40
Need 34% more for age 41-59
Need 49% more for age > 59

Darker skins need more sun
Type 1 Always burns 200-300 J/m2
Type III Burns moderately 450-600 J/m2
Type VI Never Burns 1000-2000 J/m2 (about 5X more time in the sun)

Examples for lie down, full body, black senior to get 10,000 IU
UV Index <3 730 minutes = impossible (73 minute * 2 * 5)
UV Index 3-6: About 3 hours (19 minute * 2 *5)

Need more sun if you are standing up

Note: It is not clear that more skin ==> more vitamin D: it may be a non-linear relationship
  also - some parts of the body may produce more vitamin D than other parts of the body
   - perhaps the face produces far more than the pelvis (body may learn)

See also VitaminDWiki

at is.gd/timeinsun

Response vs obesity @ /is.gd/2Xobese



  • Notional graph of vitamin D vs a few variables

IU of vitamin D to add vs X

see wikipage: http://www.vitamindwiki.com/tiki-index.php?page_id=3152