A SURVEY OF ACUTE TOXICITY OF CYCADS AND MORTALITY RATE FROM CANCER IN THE MIYAKO ISLANDS, OKINAWA*

Abstract

In 1959, the Miyako islands, Okinawa were continually attacked by typhoons and the natives who had lost their agricultural products subsisted largely on cycads. Since cycad compounds have a carcinogenic effect in a variety of laboratory animals, it is possible that they could become carcinogenic agents after ingestion in humans. The present authors attempted a statistical survey of the mortality from cancer during the years 1961 through 1966 to follow‐up the tumor incidence among these natives. Mortality from stomach cancer in the Miyako islands was lower than in interior Japan. Although there was no significant difference in death rate for hepatoma between the two, it was higher in TJeno and Irabu district. The death rate for liver cirrhosis in the Miyako islands was higher than that in interior Japan, especially it was most prominent in Tarama district. These statistical results in each district was not proportional to the rate of ingestion of cycad material during the time of famine. However, most natives in these islands have long used this plant as a food before and during World War II. High death rate for liver cirrhosis in the Miyako islands may have some correlation to such a habit of the natives. Symptoms of an acute toxicity of cycad in humans were also studied on 18 patients. ACTA PATH. JAP. 20: 327 ‐ 337, 1970.