Vitamins were named as they were discovered and when a new substance called Cholecalciferol was discovered it was mistaken for a vitamin, and called vitamin D since vitamins A, B, and C had been discovered already.
We now know that "Vitamin D" is a hormone and not a vitamin but we all go on pretending it's a vitamin!
We also know that there are different types of vitamin D and they are Vitamin D2 and Vitamin D3.
So which one do we need?
Vitamin D is produced in an inactive form when sunlight shines on the cholesterol in the skin. It is then activated in the liver and kidneys.
Vitamin D is mostly known for its ability to help the body absorb the minerals calcium and phosphate, iron, magnesium, and zinc.
And because our bones are mostly composed of a mineral reinforcement of a collagen structure this enhanced absorption of minerals due to vitamin D yield's stronger bones and protects us against rickets in children and Osteomalacia when older. More recent research shows its relevance to quality of sleep and to healing of old wounds.
Which Vitamin D To Buy
The one I buy is the Nature's Aid Vitamin D3 5000 iu at Amazon US here.
And for my UK patients D3 from Amazon UK is right here
To check your blood level of Vitamin D the NHS laboratory service is here
You may wish to measure your levels before taking D3 and then every 3 or 6 months.