Well, it makes sense that the kids with the worst diet are the ones who are in general parented the least. If they parents can;'t be bothered to try for a decent diet (I know we all have our weaknesses) then it's not too surprising they don't try to discipline or teach right from wrong ()certainly without any consistency anyway).
On a related note, there was a comedian talking about the fallacy fo marijuana as a "gateway" drug. He proposed that with that same logic, you could draw a line between milk and heroine...so he theorisec that since most heroine addicts started out drinking milk, milk must be the true gateway drug...I always keep that in mind when reading info on studies.