The reason Jews don't eat Pork, Seafood, and other Treif, is because Hashem
commanded us and told us what is Kosher and what if Treif.
It's absolutely true, that in the past, Pork was dangerous to eat if not thoroughly cooked....The same can be said for Shellfish.
Many Jews who keep Kosher, unfortunately, also get Cancers of the Colon and Rectum. As a trained Biologist and one who has studied Animal Disease and Sciences...The book, or your interpretation of the book may not be so accurate.