There are two types of Vit D.
1) Vitamin D3 produced in the skin of humans and other animals, from 7-dehydrocholesterol (a cholesterol derivative) by the action of UVB rays.
2) Vitamin D2 that occurs in plants, in the medicinal mushroom and in yeasts by solar irradiation from ergosterol.
Both vitamin D compounds cannot be used by our bodies. When absorbed, they must be transformed to produce various compounds (their metabolites), which are the active ingredients responsible for vitamin D's multiple functions in the body.
The first biologically active metabolite is 25-hydroxyvitamin D [25(OH)D] (calcidiol), which is produced in the liver from both forms, vitamin D2 or D3.
This is precisely the parameter 25-hydroxyvitamin D [25(OH)D] that is measured in the analysis to see the Vit D levels.
But traditionally, levels of this vitamin have been considered normal at between 15 and 25 ng/ml, but this doesn't mean these values are optimal. It's simply the level that shows a normal distribution in a modern society where most people don't get enough daily sunlight or eat foods rich in this vitamin.
Recently, field studies have been conducted on people exposed to the sun—just as our ancestors did—such as farmers, lifeguards, and athletes who train outdoors, and it was observed that their levels exceeded 40 ng/ml, reaching optimal levels of between 60 and 90 ng/ml.
Try to maintain high levels and supplement if necessary.
Vit D is too important.