We Pasken like Reish Lakeish of our daf that Mitzvos need intent – that one must have in mind or be aware that he is performing the Mitzva act as a Mitzva.
What if someone ate romaine lettuce – Maror on Seder night, for health reasons? Does he need to eat Maror again?
The Shulchan Aruch Paskens, that if someone was forced to eat Matza, he has fulfilled his obligation so long as he knew that it was Pesach. The Mishna Berurah explains that although he didn’t want to eat at all and by extension did not have intent to perform the Mitzva to eat, since the Mitzva is to eat and he clearly ate he has fulfilled his obligation.
However, as the Mishna Berurah points out, many Poskim disagree with the Shulchan Aruch and say that if forced to eat Matza one has not fulfilled his obligation and must eat Matza again. According to these Poskim, if one ate lettuce for health reasons, must he eat Maror again?
The Chok Yaacov holds that a Mitzva of Rabbinical nature can be fulfilled even without intent. According to him, it would seem that one would not have to eat Maror again. Here too, there are Poskim who disagree.
However Rav Yitzchok Zilberstein Shlita says, that if one did not know that he was performing a Mitzva at all, its likely that he has not fulfilled his obligation. We cannot define the act as a Mitzva, if the one performing it did not know it was a Mitzva.