Dr. do you believe that different brand names of biotin can effect hair growth? some swear, one brand works better than other? what is rec daily dose?

No good studies: There are no good studies apparently. Any that had a positive result were with a very small number of people, for decreasing nail thickness and splitting. http://www.med.nyu.edu/content?ChunkIID=21571 http://www.med.nyu.edu/content?ChunkIID=21425 http://www.nlm.nih.gov/medlineplus/druginfo/natural/313.html So brand probably does not matter. It can cause constipation.