A proper medical study also has doctors monitoring for any risks. They would run blood work and check for anything wrong - it's hard for one person to draw conclusions about how healthy this is if he wasn't baselining and monitoring different vital statistics (liver enzymes, etc.)

Also, everyone's body is different: he may just be a genetic freak who is able to do this. Especially with heath/body claims, be very wary that one person's results will be able to transfer to anyone else.