Bladderwrack

Bladderwrack is a seaweed that grows off of the North Sea coasts, western coast of the Baltic Sea, Atlantic, and Pacific Oceans. It is the original source of iodine, used extensively in the 1800s to treat iodine-deficient diseases. It is a popular type of seaweed in Japan and is used as a flavoring occasionally in Europe. It is usually found in kelp tablets, though it is not kelp. It has been found to be most useful in treating hypothyroidism because of it's iodine content. It is advised to not be consumed for hyperthyroidism, cardiac issues, during pregnancy, or in excessive amounts (which can lead to other diseases.)