Is it permissible to say, "Were it not for food, I would not have strength," or "Were it not for medicine, I would not be cured," by analogy with the hadith, "Were it not for the dark wheat, your maidens would not have become plump"?

It is permissible to say "Were it not for me, such and such would have happened" if the speaker believes that food and medicine are means, and that the effect and success come from Allah. The permissibility of attributing something to its cause is evidenced by what is authentically reported from Al-Abbas ibn Abd Al-Muttalib (may Allah be pleased with him). The prohibition of attributing influence to other than Allah Almighty is evidenced by what is authentically reported from Ibn Abbas concerning the interpretation of Allah's saying: "So do not set up rivals unto Allah while you know [that He alone has the right to be worshipped]" (Quran 2:22). However, if one attributes something to an incorrect cause, it may be shirk (associating partners with Allah).