Your body is designed to acquire the vitamin D it needs by producing it when your skin is exposed to sunlight. The sun’s rays release an natural way to get vitamin D called ultraviolet B (UVB).
There are copious amounts of vitamin D3 (cholecalciferol) are made into your skin when you expose your body to summer sun. This happens very quickly; around half the time it takes for your skin to turn pink and begin to burn. This could be just 15 minutes for a very fair skinned person, yet a couple of hours or more for a dark skinned person.
There are a number of factors that affect how much vitamin D your body produces when your skin is exposed to sunlight. These include the time of year and time of day, where you live in the world and the type of skin you have.
The amount of vitamin D you get from exposing your bare skin to the sun depends on:
The time of day – your skin produces more vitamin D if you expose it during the middle of the day.
Where you live – the closer to the equator you live, the easier it is for you to produce vitamin D from sunlight all year round.
The color of your skin – pale skins make vitamin D more quickly than darker skins.
The amount of skin you expose – the more skin your expose the more vitamin D your body will produce.