PROBLEM TO BE SOLVED: To provide a colon cancer inhibitor utilizing effects of crystalline paramylon or amorphous paramylon of a substance provided by modifying the crystal structure of the crystalline paramylon.SOLUTION: There is provided a substance for inhibiting colon cancer diseases. There are provided the colon cancer inhibitors comprising a Euglena origin paramylon, especially a colon cancer inhibitor comprising amorphous paramylon provided by making the Euglena origin crystalline paramylon amorphous. The amorphous paramylon is a substance having a relative crystallinity of &le；20% to the crystallinity of the crystalline paramylon, measured by the X-ray diffraction method. The colon cancer inhibitor can effectively inhibit generation of ACF of precancerous lesion of the colon cancer.
