This section is from the book "Practical Dietetics With Special Reference To Diet In Disease", by William Gilman Thompson. Also available from Amazon: Practical Dietetics with Special Reference to Diet in Disease.
Iceland Moss (Cetraria Islandica) is a lichen sometimes employed as food after purifying it by washing. It contains at first various bitter principles, which must be eliminated. It can be made into bread or used as an ingredient of blancmange, etc. It has been recommended by Senator and others for use by diabetics to replace ordinary bread, and it makes a convenient vehicle for the administration of fats, such as bone marrow (Walker). It also forms a good demulcent decoction.
Several forms of seaweeds are used as food by the Japanese, Siamese, and Polynesians.