If the flavonoids and other polyphenols present in the diet are CYP1 substrates, then inhibition of these enzymes appears to be disadvantageous, because most studies on the possible mechanism of the cancer-protective effect of dietary flavonoids, hydroxylated by CYP1, have assumed that free hydroxyl groups of flavonoids and other polyphenols are necessary for their biological effects (as an antioxidants). Here, CYP1A1 is linked to cancer.