Emerging studies suggest that dietary components can affect gene expression through epigenetic mechanisms. Epigenetic modifications are heritable and potentially reversible changes in gene expression that do not require changes in the DNA sequence. The main mechanisms of epigenetic control in mammals are DNA methylation, histone modifications, and RNA silencing. The potential reversibility of epigenetic changes suggests that they could be modulated by nutrition and bioactive food compounds. Thus, epigenetic modifications could mediate environmental signals and provide a link between susceptibility genes and environmental factors in the etiology of cancer. Elucidating the impact of nutrition on epigenetic mechanisms may serve as a tool to predict an individuals' susceptibility to cancer, provide dietary recommendations, or provide therapeutic applications of natural compounds against cancer. The optimal duration and the dose necessary for a chemopreventive effect require further studies. There is limited information about tissue specificity and temporal aspects of dietary treatments. Species differences need to be considered when interpreting results from various models. Importantly, molecular mechanisms of bioactive dietary components should be investigated in greater detail in human intervention studies. Although some of these issues remain controversial, this review mainly focuses on promising data that support the developing field of Nutritional Epigenetics.