Scientists at the International Agency for Cancer Research have identified certain genetic profiles that are more likely to gain protection against cancer from cruciferous vegetables, such as cabbage, broccoli, cress and sprouts.
Previous observational studies have linked consumption of these plant foods with reduced rates of lung cancer, but the mechanism for this effect has not yet been confirmed.
However researchers have shown that isothiocyanates, compounds found in high quantities in cruciferous veg, have strong chemopreventive properties against lung cancer.
The IARC team theorised that as 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 would have higher concentrations of isothiocyanates because of their reduced elimination capacity.
After further investigation, they found that people with inactive forms of the genes are indeed less likely to develop lung cancer, supporting the benefits of these compounds.
Paul Brennan and his colleagues from IARC recruited 2141 patients with lung cancer and 2168 age and sex-matched controls from six countries in eastern and central Europe to test their theory.
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 per cent 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 per cent protective effect, while those with both genes inactivated had a 72 per cent protective effect.
The investigators found no protective effect in people with active forms of the genes.
In a research letter published in this week's issue of The Lancet, Dr Brennan states: "These data provide strong evidence for a substantial protective effect of cruciferous vegetable consumption on lung cancer."