There are two types of Vit D.
1) Vitamin D3 produced in the skin of humans and other animals, from 7-dehydrocholesterol (derived from cholesterol) by the action of UVB rays.
2) Vitamin D2 is produced in plants, fungi and yeasts by solar radiation from ergosterol.
Neither of these vitamin D compounds can be used by our body. Once absorbed, they must be transformed to produce several compounds (their metabolites), which are the active compounds responsible for the multiple functions of vitamin D in the body.
The first biologically active metabolite is 25-hydroxyvitamin D [25(OH)D] (calcidiol), which is produced in the liver from either vitamin D 2 or D 3 forms.
This is precisely the parameter 25-hydroxyvitamin D [25(OH)D] that is measured in the analytics to see the levels of Vit D.
However, levels of this vitamin have traditionally been considered normal to be between 15 and 25 ng/ml, but this does not mean that these figures are optimal. It is just the level that shows a normal distribution in a modern society in which most people do not get enough time in the sun every day or consume foods rich in this vitamin.
Recently, field studies have been conducted on people who live exposed to the sun - just as our ancestors did - such as farmers, lifeguards, athletes who train outdoors and it was observed that their levels exceeded 40 ng/ml, reaching optimal levels of between 60-90 ng/ml.
Try to keep your levels high and supplement if necessary.
Vit D is too important.