Toxicity of Iceland lichen and Reindeer lichen

Abstract

Iceland lichen (Cetraria islandica) is sold in health food stores to prevent various disorders. In olden times it and sometimes also reindeer lichen (Cladonia sp.) have been used as emergency food. Lichen contains bitter and potentially toxic lichen acids and it also concentrates heavy metals. Therefore lichen toxicity was studied with traditional pretreatment methods (boiling, ash-soaking or both). Untreated and only shortly boiled lichens were lethally toxic to mice in 50 and 25% w/w mixtures in food, but when ash-soaking was added mice tolerated Cetraria (but not Cladonia) reasonably well for 3 weeks. In a 3 month test in rats 25% mixture of Cladonia was tolerated well and blood tests were normal at the end. However, urinary protein was increased, the autopsies revealed kidney changes corresponding to a mild heavy metal poisoning, as the lead concentrations in kidney and lichen were high.