While losing 50-100 hairs daily is normal, excessive hair loss — especially in women — has been linked to Vitamin D deficiency. Vitamin D stimulates hair follicles and is essential for the hair growth cycle. Severe deficiency can even trigger alopecia areata, an autoimmune condition causing patchy hair loss. The hair follicle has Vitamin D receptors, and without adequate levels, follicles can go dormant prematurely.