This is a very interesting question. I did some research as I am being treated by this too, and learned that one to two percent of people of European origin have read hair and that Vitamin b12 is one of the few vitamins Mayo Clinic recommends for older adults. I went to Google Scholar to see if there are any medical studies on your question and got zero results. When I used regular Google, I found some unscientific results, but nothing about your question. The National Institute of Health had an article about conditions associated with pale skin, but it has no answer to your question. When I posed the question “who is most likely to have vitamins b12 deficiency” the answer was people who don’t eat enough Vitamin B12 foods people who have trouble digesting it. Perhaps someone else can jump in.