LYON, France, Oct. 27 - Eating cruciferous vegetables such as cabbage and broccoli might help protect against lung cancer -- if the right genes go with them -- researches here reported today.
In persons with inactive alleles of the genes for glutathione-S-transferase enzymes, those who ate cruciferous vegetables on a weekly basis decreased their risk of lung cancer by 72% compared with those who rarely ate cruciferous vegetables.
So reported Paul Brennan, Ph.D., of the International Agency for Research on Cancer in Lyon, France, and colleagues in a case-control study published in the Oct. 27 issue of The Lancet. However, in those with active variants of the glutathione-S-transferase enzyme genes, there was no such protective effect.
Cruciferous vegetables are rich in isothiocyanates, which have been shown to have strong chemopreventive properties against lung cancer, the researchers noted. Isothiocyanates are eliminated in the body by glutathione-S-transferase enzymes produced by the genes GSTM1 and GSTT1.
Individuals with inactive variants of these genes therefore have higher concentrations of isothiocyanates because of their reduced elimination capacity and therefore may have decreased risk of lung cancer, the investigators hypothesized.
All participants completed a lifestyle and food frequency questionnaire. The researchers obtained blood samples from all participants for GSTM1 and GSTT1 genotyping. The researchers ensured that GSTM1 and GSTT1 status was not associated with important confounders such as age, smoking status, education, and dietary variables including intake of cruciferous vegetables. The researchers then calculated odds ratios for lung cancer by cruciferous vegetable consumption and genetic status.
Weekly consumption of cruciferous vegetables protected against lung cancer in those with inactive GSTM1 genes (odds ratio=0.67; 95% confidence interval= 0.49–0.91) or inactive GSTT1 genes (OR=0.63; 95% CI=0.37–1.07).
When the results were stratified by smoking status, a protective effect was seen in smokers with both genes inactive (OR 0.31; 95% CI 0.12-0.82) but not in people with both genes active. In non-smokers, there seemed to be a protective effect regardless of genotype, however the results did not reach statistical significance.
“These findings raise the prospect of an important chemopreventive effect against lung cancer for cruciferous vegetables in general, and isothiocyanates in particular,” the researchers concluded.
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