As per my food prefs post the other day, here are the results of my search for something that already does it.
Content Checked looked like a promising first result but turned out to be more about personally checking products rather than sharing your personal needs.
Then Plan To Eat also looked like it might contain the feature of sharing your preferences but it’s focused far more on the recipe sharing audience.
And finally Ingredient1 looked perfect, until the download link said it had been removed from the App Store.
Maybe that’s a sign that the idea is too small or niche to make any value from? Or maybe there’s something out there that I can’t find.