The barbarian in our last group consumed the heart of a recently slain dragon, and after 3 successive Fort saves (where failure of any one would mean the guy just could not go through with it, presumably), the DM granted him +2 Str and +4 Con.
This is bizzare- our group was just talking about this yesterday.
As a DM I suggested nothing would happen without magical "assistance" and even then it would last only a short time. Kinda like a ritual done by a Druid in Eberron.