But, despite their genetic susceptibility, they may never develop cancer if their exposure to the carcinogen is low. Likewise, those who have both active genes for glutathione S-transferase may be able to endure high exposure to the carcinogen and still escape cancer. The uncertainty remains because some studies have shown no association between broiled or grilled meats and cancers of the colon or rectum. If individuals in these studies were tested for the presence or absence of the two genes that code for glutathione S-transferase, then the results might be clearer. Glutathione S-transferase has another function beyond helping to detoxify xenobiotics.
Isothiocyanates are present in rich amounts in cruciferous vegetables.
Isothiocyanates induce enzymes that detoxify environmental carcinogens. Eight out of 12 studies of colon cancer and 5 out of 5 studies of rectal cancer found that a high intake of cruciferous vegetables reduced risk. Or conversely, the absence of these genes could increase a person's risk for colon cancer. The bottom line is that genes are not destiny. But knowing your genetic make-up could help you decide how to manage your personal environment and take the actions that are most important for you.