BACKGROUND Breast cancer prevention still needs to be improved. Calorie restriction is thought to prevent breast cancer through the induction of autophagy. Maranta arundinacea L. (MA) has the potential for calorie restriction because it contains high fiber. This research aimed to observe the effect of dietary MA against dimethylbenz(a)anthracene (DMBA)-induced mammary cancer in Sprague Dawley rats related to autophagy. METHODS Twenty-five Sprague Dawley rats were randomly divided into five groups: 1) control group without DMBA-induced with a standard diet, 2) 20 mg/kg BW of DMBA two times a week for five weeks with a standard diet, 3) DMBA and diet modification with 30% of MA, 4) DMBA and diet modification with 45% of MA, and 5) DMBA and diet modification with 60% of MA. Examination of the nodule was conducted once every week for 22 weeks. Breast tissue/tumor examination underwent histology examination with hematoxylin-eosin. Examinations of immunohistochemical staining against Beclin1, LC3B, and SQSTM1 were conducted to reveal autophagy. The difference of autophagy protein expression was analyzed using One way ANOVA with 95% confidence level and significance set as p<0.05. RESULTS Cancer was detected in four rats of DMBA standard diet, two rats of 30% MA, one rat of 45% MA. No cancer was detected in the rats of control and rats with 60% of MA group. The Beclin1 expressions showed that the 60% of MA group had the highest score (2.5±0.52) followed by the 45% of MA group (1.87±0.49), control group (1.77±0.11), 30% of MA group (1.28±0.75), and DMBA with standard diet had the lowest score (1.28±0.91). The difference of Beclin1 expressions was statistically significant (p-value=0.03). However, the difference of the LC3B expressions (p-value=0.11) and SQSTM1 expressions (p-value=0.225) were not statistically significant. CONCLUSIONS Dietary modifications with MA potentially prevent breast cancer and induce initiation of autophagy.