DNA methylation and histone modifications are two major epigenetic mechanisms that can affect gene expression through chromatin structure. Although many dietary polyphenolic compounds have strong cancer-preventive effects in various cancers, the modulating effect of dietary polyphenols on DNA methylation and histone methylation status has still not been characterized very well. DNA methylation and histone methylation. can each modulate gene expression separately, there is growing evidence that an interplay exists between cytosine methylation and histone modification to from a transcriptionally inactive chromatin state. Therefore, the ability of dietary polyphenols to inhibit DNA methylation may also modulate the key parameters of histone methylation and reactivate the expression of tumor suppressor genes in cancer cells. However, it is hypothesized that all dietary polyphenols may not be the same in terms of reactivating silenced genes and modulating the methylation status of histone proteins due to the fact that each polyphenol has varying degrees of inhibition protencies and dfficacies. More studies are warranted to further test these unknown hypotheses.