When we were in New Zealand in Dec/Jan there was a huge shortage of eggs. Sometimes you could a few, other times the shelves were completely bare. It certainly wasn’t Brexit there. Shortages happen, we’re not going to starve.
Yes, that was due to a large epidemic of bird flu in many parts of the world.
But again, when there are real shortages around the world, this makes it much worse for Brexit UK. Low currency, lots of red tape, transport issues, Channel crossing- and basically producing countries prioritising their own (as the EU will do, quite naturally, and that is not 'punishing' UK, just plain simple.
You look after your own first.