Although earlier studies have suggested that these foods might play a role in preventing lung cancer, their results were not conclusive. The latest research indicates that a person's genetic status may influence or mask this effect.

Inactive Genes

Cruciferous vegetables are rich in isothiocyanates, which have been shown to have strong chemopreventive properties against lung cancer. Isothiocyanates are sulphur-containing phytochemicals that combat carcinogens by neutralizing them, reducing their poisonous effect.

Specific genes -- GSTM1 and GSTT -- produce enzymes (glutathione-S-transferase) that eliminate these isothiocyanates from the body.

In some individuals, these genes occur in an inactive form, reducing their elimination capacity. Therefore, they retain higher concentrations of isothiocyanates when they consume foods rich in these phytochemicals.

Paul Brennan of the International Agency for Cancer Research (IARC) and colleagues looked at whether the protective effect of cruciferous vegetables was most apparent in these individuals.

72% Protective Effect

The investigators recruited 2,141 patients with lung cancer and 2,168 age and sex-matched controls from six countries in eastern and central Europe. The participants completed a food questionnaire, and the researchers assessed their genetic status from a blood sample.

In people who had an inactive form of the GSTM1 gene, weekly consumption of cruciferous vegetables had a 33% protective effect against lung cancer, the researchers found.

In those who had an inactive GSTT1 gene there was a 37% protective effect. Individuals with both genes inactivated had a 72% protective effect.

The investigators observed no protective effect in people with active forms of the genes.

"These data provide strong evidence for a substantial protective effect of cruciferous vegetable consumption on lung cancer," concludes Dr. Brennan.