In 1998, Craig Cooney and his research team in Arkansas (USA) fed pregnant brown Avy mice with different levels of methylating molecules like methionine, folic acid and zinc. The higher the supplement levels the browner, more heavily mottled were baby mice. As you might expect, browner mice were also leaner and healthier. So the mother’s diet affected the epigenetic state of her offspring including their weight and health.

Jennifer Cropley and her collaborators took this a step further in 2006, by showing that feeding pregnant Avy mice lots of methyl in their diet not only shifted the coat colours of their offspring towards the brown end of the spectrum, but also affected the next generation in the same way. So the grandmother’s diet affects the epigenetic state of her grandchildren.

Traditionally, scientists thought that methylation marks were removed from DNA as it is packaged into germ cells, wiping the epigenetic slate clean for next generation. But Cropley’s experiments suggest that – at least for the Avy gene – some marks must remain, raising questions about the very nature of heredity.

Can diet and other lifestyle factors influence future generations? Might this be true for humans and/or relevant to obesity? Because the Avy experiments were performed on inbred, genetically identical strains of mice – a far cry from our own diverse genomes - drawing parallels with Dutch mothers, albeit tantalising, requires further support.