Fig. 2.
Percentage of pre-vitamin D3 formed after exposing ampules containing 7-dehydrocholesterol (7-DHC) to a portable tanning machine at several times and distances (◆, 14 inches; ■, 20 inches; ▲, 26 inches). Ampules containing 7-DHC (pro-vitamin D) were exposed to a portable tanning machine at several distances and times to determine the optimal conditions for vitamin D production in the skin. Vitamin D production was optimal at 14 cm from the device and an exposure time between 10 and 15 min.