Interesting study apparently showing interaction of genotype and foods:
Study: Eating cruciferous vegetables prevents lung cancer
By David Liu, Ph.D.
Oct 28, 2005, 15:23
Eating cruciferous vegetables such as broccoli and cauliflower may reduce the risk of contracting lung cancer, according to a French study published in the Oct. 27 issue of The Lancet.
The researchers found among the population that carries inactive genotypes pf GSTM1 and GSTT1 that, of this group, whoever ate cruciferous vegetables weekly were 72 percent less likely to have lung cancer compared with those who did not eat the vegetables.
Numerous studies have already associated eating cruciferous vegetables with a lower risk of lung cancer, although such an association was not found in all studies. Some researchers attributed the discrepancy of findings to the difference in genes.
Two genes responsible for the chemopreventive activity of cruciferous vegetables were identified in previous studies as GSTM1 and GSTT1. The genes direct the production of glutathione-S-transferase enzymes, which are involved in the detoxification of toxic compounds, which include isothiocyanates. Isothiocyanates are known to be the active anticancer chemicals present in cruciferous vegetables.
In a study of over 400 Chinese women (published in the Oct. 10, 2001 issue of Cancer Epidemiol Biomarkers Prev.) Zhao B and colleagues from the National University of Singapore reported that nonsmokers with a GSTM1-null genotype, who had high intake of isothiocyanates, were 56 percent less likely to have lung cancer. The inverse association was not found among those with detectable GSTM1.
The current case-control study by Paul Brennan, Ph.D., of the International Agency for Research on Cancer in Lyon, France, apparently confirmed that consuming cruciferous vegetables may only benefit those with inactive genotypes of GSTM1 and/or GSTT1.
The study investigated the association between dietary isothiocyanate intake, GSTM1 and GSTT1 polymorphisms, and lung cancer risk. The study used 2,141 patients with lung cancer and 2,168 control patients from six countries in eastern and central Europe.
The dietary habits of the participants were surveyed using a lifestyle and food frequency questionnaire. Blood samples from the participants were taken for genotyping GSTM1 and GSTT1.
After considering other interfering factors, the researchers found weekly consumption of cruciferous vegetables was associated with a reduced risk of lung cancer in those with inactive forms of GSTM1 and GSTT1. This is compared with those who did not eat the vegetables. The risk in those with inactive GSTM1 and GSTT1 was reduced by 33 and 37 percent respectively.
Those with both inactive GSTM1 and GSTT1, who ate weekly cruciferous vegetables, were 72 percent less likely to have lung cancer compared with those who did not eat the vegetables. A strong effect was also found in the smoking participants. This result was consistent with Zhao B’s findings.
The protective effect of cruciferous vegetables was also found in non-smokers, regardless of the genotype, although the association was less significant.
The researchers explained that people with inactive GSTM1 and GSTT1 lack or have no sufficient glutathione-S-transferase enzymes to metabolize isothiocyanates. Because of this, isothiocyanates can accumulate to a level where they exert an effect in those with the inactive forms of GSTM1 and/or GSTT1.
Isothiocyanates are not the only compounds in cruciferous vegetables that possess chemopreventive properties. Many others also have the effect on lung cancer and many other cancers.
The common cruciferous vegetables include cabbage, cauliflower, broccoli, Brussels sprouts, mustard greens, collard greens, kale, turnip greens and kohlrabi.
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