Whole grain consumption has a favorable effect on fasting concentrations of glucose and insulin that is unaffected by genetic variation at loci that influence glucose and insulin levels, report Nettleton et al.

The researchers investigated the gene–diet interactions in a 14-cohort meta-analysis that included data of ∼48,000 individuals of European descent who did not have type 2 diabetes mellitus when fasting levels of glucose and insulin were measured; participants' genotype at 16 glucose-related single nucleotide polymorphisms (SNPs) and two insulin-related SNPs was also determined.

The researchers found a strong inverse association between the amount of whole grain intake and fasting glucose or insulin levels, which persisted after adjustment for a number of potential confounders, including sex, age, energy intake and BMI. The inverse association held true regardless of allelic variation at most of the loci tested; however, presence of the insulin-raising C allele in the SNP located in the glucokinase (hexokinase 4) regulator (GCKR) gene seemed to dampen the beneficial insulin-lowering effect of greater whole grain intake.

Could dietary therapy be individualized to a patients' genotype? The researchers hope to find out with further studies of gene–diet interactions. “Obvious next steps would be to expand our focus from just a few SNPs to the multitude available in genome-wide association studies. We are also interested in the possible interaction we noted between GCKR and whole grain intake”, concludes lead researcher Jennifer Nettleton of the University of Texas.