Toggle Health Problems and D

Getting a tan does not mean that you are getting vitamin D

When the sun is low in the sky (not summer, early in the day, late in the day) there is significantly more UVA than UVB

Under those conditions you can tan but get very little vitamin D
Note: Example: UVA >> UVB when you are standing (cylinder) and the solar zenith angle is say 30 degrees (close to the horizon)

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From Sun and Sun Beds: Inducers of Vitamin D and Skin Cancer- 2009 file from ANTICANCER RESEARCH: 2009

See also VitaminDWiki

Very little of the tanning bulb intensity actually generates vitamin D