Variations in both the genome and epigenome can affect individual nutrient requirements. In order to optimise nutrient intake for good health, it becomes important to understand the way in which nutrients affect the expression of key genes. Epigenetic events imply a change of gene expression without a heritable change in DNA base pairs. These events may result from the action of transcription factors, the methylation of certain DNA bases, changes in chromatin structure through various histone modifications, or the action of non-coding RNAs. Each these classes of events is susceptible to both dietary and environmental influences. Transcription factors trigger gene expression in response to external signals, including certain dietary lipids. Changes in DNA methylation can occur directly, through an imbalance in the methyl donor pool. The key nutrient implicated here is folate, but vitamins B6 or B12, betaine, choline and selenium all play established roles. Dietary effects on DNA methylation may also occur indirectly, through inhibition of DNA methyltransferase enzymes. Inhibitors of such enzymes include various phytochemicals, including a range of polyphenols, such as epigallocatechin gallate, from green tea, or isothiocyanates, which are common in Brassicaceous vegetables. Post-translational modifications of histones play a key role, not only in regulating chromatin structure and gene expression, but also in genomic stability. A range of dietary compounds have been implicated as histone deacetylase inhibitors, including butyrate (produced through the digestion and fermentation of dietary fibres) and isothiocyanates. Single nucleotide polymorphisms in genes affecting methyl donor pools may impact individual susceptibility to epigenetic events, and these will be profoundly influenced by diet, not only pre-conception, but throughout the lifecycle. This paper addresses a hitherto neglected dimension in human nutrigenomics science literature – epigenetics and the importance of dietary effects on the epigenome - in the overarching context of tailoring diets to match peoples genetic make-up.
Epigenetics, DNA methylation, methyl donor imbalance, methyltransferase inhibitor, histone deacetylase inhibitor
Discipline of Nutrition, Faculty of Medical&Health Science, The University of Auckland, Private Bag 92019, Auckland, New Zealand.