would consumption of twili food have any effect on the bodys natural magic? what would happen if a hyrulean decided to live in the twilight realm for a long time?

Outside of getting a Light Dweller acclimated to the magic and atmosphere of the Twilight Realm? Not really. They’d have to consume a shit ton for it to do anything to them, but that would only happen if the Light Dweller decided to live in the Twilight Realm.

Living in the Twilight Realm would affect the magic of the Light Dweller due to them passively absorbing the magic in the atmosphere, as well as prolonged exposure to the realm in general. They’d probably have increased ability in magic, given how dense the Twilight Realm is with it (moreso than the Light Realm), as well as gain an affinity for Twilight Magic in general. Their appearance wouldn’t change but they would become a little more sensitive to the sun, a trait seen in all Twilight dwellers, so wearing a hood or cloak (or using an umbrella) and eye protection is usually a common part of their wardrobe if they ever go back to the Light Realm again.