Alzheimer’s disease and the lack of vitamin D

What is the link between AD (Alzheimer’s disease) and vitamin D? We have two ways to get the vitamin D, first, when the sun converts a cholesterol molecule from our body (7 dehydrocholesterol) into vitamin D (inactive form), which in turn is converted in the active form, or second, by taking vitamin D supplements (ideal if we work on nightshift or we stay a lot inside a building, or we wear a lot of clothes covering most of our skin, or too much sunscreen cream, or in the winter when the day is shorter — September to March). Once the active form of Vitamin D is present in our…