Vitamin D stimulates hair follicles, so a deficiency may lead to hair loss. There is some evidence that having a vitamin D deficiency does cause hair loss and other hair problems. Vitamin D stimulates hair follicles to grow, and so when the body does not have enough, the hair may be affected
https://nutritions4.com/hair-revital-x/
https://nutritions4.com/hair-revital-x/