In Catalonia we have one saying “eat stalk raisin” (“menja cues de pansa”). We say it when someone forgets something.
I know that in Alicante zone they say “tienes que comer más pescado” (“you must eat more fish”). And in Morocco they say “eat more liver” (see the Morocco entry, Mustapha is who said so).
I’m quite sure that the liver or fish sayings may have some scientific explanation. Not sure about the “stalk raisin”. I like to know what different countries say about the same topic. I should search for some other ones!