The MidrashAvot de Rabbi Natan, states: Midrash (pl. ...
One time, when Rabban Yochanan ben Zakkai was walking in Jerusalem with Rebbi Yehoshua, they arrived at where the Temple in Jerusalem now stood in ruins. "Woe to us" cried Rabbi Yehoshua, "for this house where atonement was made for Israel's sins now lies in ruins!" Answered Rabban Yochanan, "We have another, equally important source of atonement, the practice of gemilut hasadim (loving kindness), as it is stated 'I desire loving kindness and not sacrifice'".
Rebbi Eliezer maintains that a person becomes Tamei with the same degree of Tum'ah as the food that he eats, whether he eats food that is Tamei with Rishon, Sheni, or Shelishi l'Tum'ah.
RebbiYehoshua argues and maintains that when a person eats food that is Tamei with Rishon l'Tum'ah or Sheni l'Tum'ah, he becomes Tamei with Sheni l'Tum'ah.
RebbiYehoshua claims that a person cannot attain even a Tum'ah *equal* to the Tum'ah of the food that he ate, unless there is a precedent for such a thing.