Customized Diets for Cancer Prevention According to Genetic Polymorphisms: Are We Ready Yet?

Extract

Since the early 1990s, numerous studies have examined gene-gene and gene–environment interactions in relation to disease risk. Of particular interest are data on how nutrient intakes modify genetic susceptibility to diseases, which may provide scientific bases for formulating preventive strategies through dietary modification. The enthusiasm in this scientific pursuit has been put into action by entrepreneurs who sell dietary recommendations and/or dietary supplements claimed to be tailored to one's genetic susceptibility to disease. Catchy terms such as “nutrigenetic testing,” “personalized supplements,” “feed your genes right,” and “intelligent diet” have been created and used to attract customers.

In this issue of the Journal , Lewis et al. ( 1 ) report the findings from their systematic reviews and meta-analyses of observational studies of dietary folate intake or circulating folate levels and breast cancer and of the C677T polymorphism in the methylenetetrahydrofolate reductase (MTHFR) gene, which encodes a key enzyme in folate metabolism, and breast cancer. Their meta-analysis of the data from 13 case–control studies of folate intake suggested that for every 100-μg increase in folate intake, women were 9% less likely to develop breast cancer. One important finding of this analysis was evidence of publication bias among the case–control studies, such that small studies showed a greater magnitude of association between folate intake and breast cancer risk. Overall, none of the nine cohort studies included in the meta-analysis showed a significant association between folate intake and breast cancer risk, and limited data suggest no association between folate supplementation and breast cancer. Lewis et al. ( 1 ) also found no statistically significant difference in breast cancer risk between women with the MTHFR C677T TT genotype and women with the MTHFR C677T CC genotype and no evidence of a statistical interaction between folate intake and MTHFR genotypes.