The purpose of this study was to determine whether a mineral-rich extract derived from the red marine algae Lithothamnion calcareum could be used as a dietary supplement for chemoprevention against colon polyp formation. A total of 60 C57bl/6 mice were divided into 3 groups based on diet. One group received a low-fat, rodent chow diet (AIN76A). The second group received a high-fat "Western-style" diet (HFWD). The third group was fed the same HFWD with the mineral-rich extract included as a dietary supplement. Mice were maintained on the respective diets for 15 months. Autopsies were performed at the time of death or at the completion of the study. To summarize, the cumulative mortality rate was higher in mice on the HFWD during the 15-month period (55%) than in mice from the low-fat diet or the extract-supplemented high-fat diet groups (20% and 30%, respectively; P < .05 with respect to both). Autopsies revealed colon polyps in 20% of the animals on the HFWD and none in animals of the other 2 groups (P < .05). In addition to the grossly visible polyps, areas of hyperplasia in the colonic mucosa and inflammatory foci throughout the gastrointestinal tract were observed histologically in animals on the high-fat diet. Both were significantly reduced in animals on the low-fat diet and animals on the extract-supplemented HFWD.These data suggest that the mineral-rich algae extract may provide a novel approach to chemoprevention in the colon.