Used to go sea fishing some years ago. National Post Office Champion, 1991, don't you know!
Dug my own bait from the local beach. Big black lugworm known locally as yellow tails because of the iodine they contained. Much more attractive to fish than the Common Lugworm, arenicola marina.
Was all this extra iodine scent in the water the main attraction? Decided to test the idea. Bought some iodine, watered it down, added it to some sawdust on newspaper and added some black lug.
Within 2 hours all the worms were dead!
Moral - what's good on the inside isn't necessarily good on the outside.