To unravel the link between epigenetics and diet, let’s step back to World War II (watch out for that unexploded shell!) and the so-called 'Dutch mothers'. A group of pregnant women living in the Netherlands, labouring under starvation conditions imposed by a harsh winter and food embargo, gave birth to relatively small babies. When their children grew up, in relative prosperity, to have children of their own their babies were unexpectedly small. So the effects of poor nutrition on Dutch mothers carried through to their grandchildren. The study seemed to support the scientific heresy of Lamarckism – the idea that physical changes acquired during an individual’s lifetime could be passed on to their offspring. But how can diet affect inheritance, given that it can’t change the DNA sequence in eggs or sperm?

We now know that the effect seen in the Dutch families arose from changes to epigenetic markers on their DNA, caused by the deficiency of crucial molecules in the diets of the grandmothers. One of the most important epigenetic changes is methylation (see What Neil says) which usually labels genes that are switched off. In order to faithfully maintain the correct patterns of methylation through cell division, new methyl groups are stuck onto freshly-copied DNA. This requires a constant supply of new methyl groups, which can be provided directly from our food, including the trio of molecules methionine, betaine and choline. Alternatively, we can make methyl groups from precursor chemicals, including folic acid.

Other chemicals from food are needed to transport the methyl groups within the body, and attach them safely to DNA. For example: vitamin B-12 and the mineral zinc. Deficiencies in these essential molecules can have effects on levels of DNA methylation in the body, as revealed by studies in rodents and humans. In the case of the Dutch mothers, it’s likely that their meagre rations deprived them of the nutrients they needed to set up the correct patterns of methylation in their offspring, and that these epigenetic quirks were also passed on to the next generation.