Curious if anyone has been using creatine for a longer period e.g. a year or more? I've been using it for about 3 months now, 5g a day. I feel like it has made a difference not only physically but also with my mental acuity. That said, I just changed medical clinics and saw a new doctor for the first time. When I mentioned I was using creatine, he freaked out and said I had to quit immediately as it did serious damage to kidneys. Everything I've read said that in small quantities it wasn't an issue. Any comments?