By Rabbi Berach Steinfeld
The mishna in Avos, Perek Gimmel, mishna ches says that if one forgets his learning it is as if he is chayev misa (capital punishment.) The gemara in Menachos says when one forgets his learning he is over on three lavin.
Meseches Horiyus lists types of food that causes a person to forget his learning if he partakes of them. If one eats from these foods does he fall under the category of the mishna in Avos and the gemara in Menachos?
The Sefer Chassidim brings a story of someone who asked his Rebbe the following question. In a normal circumstance he would not eat from foods that were eaten by a mouse, but he was so desperately poor and had no other food and was literally starving. Would it be permissible for him to eat food that had been nibbled on by a mouse? The Rebbe told him it would be permissible for him to eat it since he is not oiver on the lav of forgetting his learning since he is not doing a ma’aseh that will make him forget his learning. It is at best a grama.
We could explain the above question based on a machlokes Rishonim. The Rabbeinu Yona says the reason why one should be careful to remember his learning is so that he should not come to pasken incorrectly. According to this opinion, it would stand to reason that one should not be allowed to eat anything that will cause him to forget; he should therefore be able to pasken correctly.
The Rashgatz argues with Rabbeinu Yona concerning this and says the reason is not because he might pasken incorrectly; because we find in the gemara if a Rov forgot his learning and paskens incorrectly he is not liable. We see that the reason one should not forget his learning is not because of paskening, but rather that there is a mitzvah to remember what one learns and an issur to physically cause oneself to forget his learning. In this case, there would be no issur of eating these foods because it is not a guarantee that it will cause him to forget and he is not physically doing something to directly cause him to forget his learning.
There is a machlokes Achronim whether one who eats these foods is oiver on a lav or not. The Chazon Ish and the Sheilos U’Tshuvos Lehoros Nosson pasken that one is oiver on a lav if he eats from the foods that cause one to forget. Conversely, the Shailos U’Tshuvos Divrei Malkiel and Reb Chaim Kanievsky say there is no lav since there is no guarantee that he will forget his learning. However, they conclude that if one does eat these foods they are considered a mezalzel in Divrei Chazal.
I would say that we should forget about eating those foods.