Whether the consumption of cruciferous vegetables, such as cabbage, broccoli and sprouts, protects against lung cancer is unclear. Some observational studies have shown a protective effect. But a person's genetic status may influence or mask this effect. Cruciferous vegetables are rich in isothiocyanates, which have been shown to have strong chemopreventive properties against lung cancer. Isothiocyanates are eliminated in the body by glutathione-S-transferase enzymes produced by the genes GSTM1 and GSTT1. People who have inactive forms of these genes therefore have higher concentrations of isothiocyanates because of their reduced elimination capacity. Paul Brennan (International Agency for Cancer Research) and colleagues looked at whether the protective effect of cruciferous vegetables was most apparent in these individuals.
The investigators recruited 2141 patients with lung cancer and 2168 age and sex-matched controls from six countries in eastern and central Europe. The researchers gave participants a food questionnaire to fill in and assessed their genetic status from a blood sample. They found that weekly consumption of cruciferous vegetables had a 33% protective effect against lung cancer in people who had an inactive form of the GSTM1 gene. In people who had an inactive GSTT1 gene there was a 37% protective effect, while those with both genes inactivated had a 72% protective effect. The investigators found no protective effect in people with active forms of the genes.
Dr Brennan states: "These data provide strong evidence for a substantial protective effect of cruciferous vegetable consumption on lung cancer."