The body produces from 10,000 to 25,000 international units of vitamin D-3 from sunlight when exposure lasts long enough to turn the skin pink, according to the Vitamin D Council. The body also derives some vitamin D from dietary sources, although the amount absorbed depends on the food consumed.
The amount of vitamin D-3 absorbed via skin depends on several factors, notes the Vitamin D Council. The time of day of sun exposure affects the amount of vitamin D-3 the skin produces. Exposure during the middle of the day causes the body to produce more vitamin D-3 than exposure at other times. Also, proximity to the equator affects absortion levels, with higher levels absorbed nearer to the equator.
Vitamin D-3, also called colocalciferol, is vitamin D in its natural form produced by the body, reports WebMD.