Iodine deficiency has come up here before, a real danger if you're on short rations and away from the sea coast. Caught mention of the term 'goiter belt on survivalblog.com and sure enough it's a real thing from the old days, eliminated in our time by the use of iodized salt. Deficiencies are reportedly coming back though no doubt due to the phobia about salt intake. There's a map of the Belt at the link, only shows the US though, and not Canada. But it's a safe bet we're the same or worse.