Why can epidemiologic studies give us a clear answer about the cancer-protective effects of cruciferous vegetables?
Recent research suggests that genetic factors affecting the metabolism of glucosinolate breakdown products may influence the relationship between cruciferous vegetable intake and cancer risk. Glutathione S-transferases (GSTs) are a family of enzymes that metabolize a variety of compounds, including isothiocyanates from cruciferous vegetables, in a way that promotes their elimination from the body. Genetic variations that affect the activity of GSTs have been identified in humans. Specifically, individuals who inherit two copies of the GSTM1-null or GSTT1-null gene cannot produce the corresponding GST enzyme. Lower GST activity in such individuals could result in slower elimination and longer exposure to isothiocyanates after cruciferous vegetable consumption, thus enhancing cancer prevention. In support of this idea, several epidemiologic studies have found that inverse associations between isothiocyanate intake from cruciferous vegetables and the risk of lung cancer or colon cancer we
