About 15 years ago, I knew a fisherman from what we call the HILLS, or southern Ohio. He knew a feller that was born and as a baby, nothing agreed with him, his body rejected just about everything. The family finally just fed him what was natural and nothing from a store. This boy grew up loving Nature and moved off into the deep woods and lives off the land as they did hundreds of years ago, he is still friendly to his kin, but won't eat anything but what God gives him freely and my ole fishing buddy said this guy was in the best shape and strength stronger than anyone he knew.
This is why many old doctors wrote books about returning to Nature.