Jarvis wrote a book called Folk Medicine. During his life he was quite aware of the denatured aspect of "modern" processed, industrial foods and urged people to limit their consumption. He believed and stated correctly that every industrial step which food is subject to in processing diminishes its nutritional benefit.
Later, macrobiotic theory espoused a similar view.
When considering how much Iodine to use consder this statement from Jarvis,
"Every element necessary for life is present everyvhere in the sea. Sea water and healthy human blood have an almost identical chemical constituency."