I was reading about Shinto mythology as part of a class assignment, and one of the stories involved a man, Izanagi, going to the land of the dead to get back his sister/wife. Unfortunately, by the time he arrives, Izanami has already eaten food from the underworld and can never leave again.
This sounded eerily similar to the story of Persephone and the pomegranate seeds, so I went to see if either of them influenced the other. I didn't find any information on that, but I did learn that there's another similar myth regarding eating food in the land of fairies.
Does this specific myth that eating food while in supernatural realms have a known origin, or is it all just a coincidence?
This isn't itself an answer, but here's a third version for you.
There's a story from the Kwagiulh tribe of the North American Pacific Northwest, as recorded by Franz Boas and George Hunt in the Kwakiutl Tales. A living woman follows her recently-deceased husband into the other world, and eats some berries despite being warned not to. She's allowed to return to the living world, but her mother discovers her newborn grandson is a ghost/corpse baby. (It's not explicitly blamed on the berries, though.)
It's possible that the storyteller here was familiar with the Persephone myth; there are some other parallels as well. On the other hand, it's not an obvious retelling either; structurally and thematically it seems like a Northwest Coast story through and through, it's just a few details (like being forbidden to eat, and there's a river and a ferryman) that are strikingly familiar.
Source: Franz Boas. 1910. Kwakiutl Tales. New York: Columbia University Press.