In terms of blood-borne viruses (like HIV and hepatitis), breast milk is considered in the same risk category as semen or vaginal secretions, only blood is higher. Whereas piss and shit are only considered a risk if they contain blood. Obviously there’s other reasons why you don’t want shit in your food, but it probably won’t give you anything really nasty and long-lasting. Piss it’s pretty much totally safe, but I reckon you could still get in trouble for secretly feeding it to someone.