Cycad Flour Used by Guamanians: Effects Produced in Rats by Long-term Feeding

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Abstract
Male and female rats were fed diets containing home-made cycad flour for about 23 months to determine whether the flour was carcinogenic. This cycad flour was processed by Guamanians for human consumption. Continuous ingestion of nutritionally adequate diets containing 1.5, 5.0 or 10.0% home-made cycad flour did not affect growth rates of rats significantly. However, a sudden drop of environmental temperatures caused a greater loss of body weights of transient nature in the treated rats than in the controls. Activity of the male rats measured by revolving cages was not significantly different between the control and treated rats. At the termination of the experiment, 11 of 45 experimental rats had died or were moribund, whereas all of the 15 control rats appeared to be in good health. Tumors and hyperplastic processes in organs of the endocrine system as well as reticulum cell sarcomas found at autopsy at the termination of investigation were thought to be related to the advanced age of the animals rather than to the ingestion of processed cycad flour. No neoplastic lesions were observed such as those noted previously following long-term ingestion of unprocessed cycad flour. These observations suggest that the local customs of preparing cycad flour by soaking, if properly executed, removes the carcinogenic substance effectively.