Re: Iodine-deficient soils in the U.S. the "goiter belt"

Soils derived from granite seem to be generally deprived of minerals in general. Hard to say what soil samples (farm or forest) were used to determine the map. But from the map in your post you can imagine where the line of glacier had dropped down from the north.

The maps of Iodine deficient soil and the regions where walnut trees flourish seem to overlap only slightly in southern Michigan, northern Ohio, Indiana & Illinois and southern Minnesota, Wisconsin, (all goiter belt states), all of Iowa and parts of eastern Texas and Nebraska.

Walnut tree range in U.S.


Regional map of Iodine deficient soils.

Isn't there a test one can do at home with vitamin C to help determine whether the walnut hull contains this trace element? If not, then I suppose it would be wise to find out where your Black-Walnut hulls are harvested from, to be more or less certain as to whether it contains iodine.
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