hey there,
i m not a theater professional, but I think the "abuse" of food in Phaedra's love underlines Hippolytus' greed, iniciated through his continous boredom of life. he tries to fill and stuff himself by consumation, food and sex, one of the basic elements of human life.
On the other side, Ian (Blasted) is in such a devasted state of self that there doesn't remain a lot apart from hunger- hunger for life, and even for hope which he priorly didn't express verbally. He lost his ability of communicating, so he finds himself isolated within the closest person and finds a relief in eating a baby. I mean, come on, eating the young life, a newly born baby simplify signifies (to me) pure, innocent and NON-depressing life. More questions?