There is considerable epidemiological evidence that a diet rich in cruciferous vegetables may reduce the risk of various cancers. These benefits have been associated with the presence of glucosinolates, sulfur-containing glycosides, that degrade during and after consumption to isothiocyanates and indoles, which have anticarcinogenic activity.

The consumption of broccoli has been specifically linked with a reduction in the risk of cancer. Sulforaphane is a dietary phytochemical obtained from broccoli that has been implicated in several physiological processes consistent with anticarcinogenic activity, including enhanced xenobiotic metabolism, cell cycle arrest and apoptosis. Depending on how broccoli is processed, sulforaphane may be absorbed through the stomach, small intestine or colon.

After passive diffusion into epithelial cells, sulforaphane is rapidly conjugated with glutathione and transported into the blood stream. However, the precise nature and concentration of the conjugates circulating in the plasma has not been fully clarified. In addition, there is uncertainty about the extent to which the induction of detoxification enzyme in vivo accounts for the anticarcinogenic activity of sulforaphane or broccoli. Several studies have reported the ability of sulforaphane to induce apotosis in a range of cell lines, but the physiological processes have not been fully elucidated.

A study by Traka et al.¹ investigated changes in global gene expression in Caco-2 cells exposed to different concentrations of sulforaphane using transcriptome analysis. A total of 169 genes that are highly likely to be altered in expression after exposure to sulforaphane were identified. Several of these genes are involved in diverse biological processes that are implicated in carcinogenesis. The results suggest the complex effects of sulforaphane on gene expression and potential mechanisms by which the consumption of broccoli may reduce the risk of carcinogenesis.

¹ Traka, M; Gasper, AV; Smith, JA; Hawkey, CJ; Bao, Y; Mithen, RF (2005). Transcriptome analysis of human colon Caco-2 cells exposed to sulforaphane. Journal of Nutrition 135 (8) 1865–1872.

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