Overview Skin and vitamin D has the following chart for UV when standing
Chart edited to show when shadow length = your height (sun angle = 45 degrees)
Sun Friend would indicate that you are getting a lot of UV, but only 1/4 of it is the UVB needed to make Vitamin D
Until a new version of Sun Friend is available which includes compensation for sun angle (= location & time of year & time of day)
Sun Friend should only be used to estimate vitamin D at local noon +- about 2 hours in the summer
Note: I spoke July 2015 with developers about this limitation.
People wearing the UVA+UVB watch would learn to keep out of the hottest portion of the sun (which actually has the vitamin D) because their watch would (falsely) tell them that they would get lots of vitamin D is the late afternoon - when it is not as hot.
- Getting a tan does not mean that you are getting vitamin D
- Vitamin D protects DNA against UV skin damage – 5 studies 2012-2013
- All items in category UV and Vitamin D
- UVA decreased serum levels of vitamin D - RCT Oct 2012
- Another vitamin D meter fails to distinguish UVB from UVA – Violet – Dec 2014
- UVA decreased vitamin D levels (again) – July 2013
Perhaps the high UVA vs UVB in the late afternoon would actually DECREASES the vitamin D levelsA wrist-watch which measures UVA plus UVB - should NOT be used to increase vitamin D - June 2014
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