The belief in Judaic law was that the spirit stays with the body for 3 days and there was hope to come back. It's why the story of Lazarus was a big deal in the Bible. I'm not sure how relevant that is to a situation like this but it's why I get paranoid of people who say they've seen heaven or hell after being pronounced dead for a day.

If your uncle is adamant on that point have you tried convincing him to veganism or is he one already? Feel like there's probably a real good argument for veganism there too.