Posted this once and it didnt go through. But I seen this first hand years ago. I was going through Leukemia IV's saline. But there was an old black man that was getting sicker and sicker. One day he came in looking gray and I mean gray. Didnt look black at all. The next day he wasnt there. Two days later he returned looking fantastic. His color returned, he was talkative and even looked younger. We all asked what happened and he said "He gave me some of that young blood" Meaning he got a transfusion. Months later he still died but I'll never forget it. Also, if you donate blood, they do not use a person that is 49 years are older for transfusion. Only for blood products like medicine.
I remember that theory. Didn't care for it.