Vitamin D plays so many roles in the development of alopecia that I regard it worth detailing. Allergies induce vitamin D deficiency via a complex pattern of inflammatory signaling involving TGF-beta and prostaglandin production. Vitamin D regulates bone mineralisation and helps to maintain osteoblast calcium homeostasis. Vitamin D deficiencies have been linked to the development of alopecia. Vitamin D inhibits interleukin expression. Finally, mutations of the genes which direct construction of vitamin D receptors are directly implicated in patterns of non-male pattern baldness; reducing signaling/reactions resultant from binding of vitamin D and specific steroid hormones to those receptors. Although such mutations are specific to those types of baldness there have been studies of the specific genes which make alopecia areata more likely to occur. The list is quite extensive and it's likely that the more of such nonsense gene mutations are present in an individual the more predisposed the individual is to developing male pattern baldness. The real trick, in preventing this from occurring or reversing it, seems to be to understand the process, avoid allergens and toxins, and provide necessary nutrients to ensure bone and hair health.