Acorus calamus
In 1968 the Food and Drug Administration banned "Acorus calamus" from being used as a food additive and as a medicinal as a result of lab studies that involved supplementing the diets of lab animals over a prolonged period of time with massive doses of isolated chemicals (β-asarone) from the Indian Jammu strain of "Acorus" "calamus". The plant was labeled procarcinogenic. Wichtl says "It is not clear whether the observed carcinogenic effects in rats are relevant to the human organism." However, most sources advise caution in ingesting strains other than the diploid strain.