Cruciferous vegetables in cancer prevention

Epidemiological studies have reported a strong inverse correlation between the intake of cruciferous vegetables and the cancer risk. This association has been found stronger than the association between cancer risk and fruit and vegetable intake in general. Cruciferous vegetables are unique in that they are rich sources of glucosinolates. Hydrolytic degradation of glucosinolates results in the formation of biologically active compounds, including indoles (such as I3C - indole-3-carbinol, DIM - diindolylmethane, indole phytoalexins) and isothiocyanates (such as PEITC - phenethyl isothiocyanate, SFN - sulforaphane). Some mechanisms, like effect on biotransformation system, induction of cell cycle arrest and apoptosis, and antiangiogenic effect, by which cruciferous vegetables act as chemopreventive agents have been described. Beneficial modulation of oestrogen metabolism with reduced risk of breast and cervical cancer after DIM and I3C supplementation was noted. Despite all health benefit expectation, some studies found that I3C actually promoted or enhanced the development of cancer when administered chronically after the carcinogen (post initiation) to rats. Because the long-term effects of the supplementation of the mentioned compounds on cancer risk in humans are not known, the widespread use of dietary supplements containing natural compounds in humans should be avoided until the potential risks versus benefits are better understood.