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You would need 1) the sun to actually be shining, 2) no cloud cover and 3) probably be naked. Most of us won't get enough vitamin D from being outside for an ho
by dkersten 9y ago
You would need 1) the sun to actually be shining, 2) no cloud cover and 3) probably be naked. Most of us won't get enough vitamin D from being outside for an hour.
- mkempe 9y ago1. The key UV for vitamin D production by our skin are UVB rays, optimal between 10am and 2pm, except in the winter at 40+ latitude when the rays travel longer through the atmosphere due to the low solar angle. For instance in Washington state your skin cannot produce vitamin D from November to February. 2. UVB do pass through clouds. (But not through glass windows.) 3. Arms and face exposure are sufficient if you spend 10, 20, or 30 minutes a day depending on UV index of the day (the higher the UV index the less time you need to trigger vitamin D production) and on your skin color. There is some kind of "reservoir" effect that limits production of vitamin D to a maximum, so sun exposure time beyond the above does not have any benefit in terms of vitamin D production.