Question

Vitamin D synthesis in the skin is affected by all of the following EXCEPT ________.
use of sunscreen
skin color
geographic location
All of these factors can affect vitamin D synthesis

Answer 1

normal synthesis of Vitamin D...first thing is that Vitamin D is a hormone, not a vitamin.

For most people sunlight exposure is the primary source of vitamin D. in skin epidermal layer the precurser 7-dehydrocholesterolis is esposed to solar ultraviolet-B radiation (UVB; wavelengths of 290 to 315 nanometers)  and stimulates the production of vitamin D3.This Vitamin D3 enters the circulation and is transported to the liver, where it is hydroxylated to form 25-hydroxyvitamin D3 and this The circulating 25(OH)D level is an indicator of the vitamin D status.25(OH)D is converted in the kidney to its active hormonal form 1,25-dihydroxyvitamin D (1,25(OH)2D; calcitriol) in a process which is usually tightly controlled by the parathyroid hormone.

so overall .....

Vitamin D is produced in the skin when it’s exposed to UV radiation from the sun.

and if we use the sunscreens so it prevent the sun’s UV radiation from penetrating the skin and therefore may diminish production of vitamin D.

same happened with other mentioned factors as environmental factors such as geographic latitude, season, time of day, weather conditions (cloudiness), amount of air pollution and surface reflection which can all interfere with the amount of UVB radiation reaching the skin.

so the answer is quite obvious i.e. All of these factors can affect vitamin D synthesis