The Dutch famine of 1944 was a terrible time for many in the Netherlands – with around 4.5m people affected and reliant on soup kitchens after food supplies were stopped from getting into the area by German blockades. As many as 22,000 people were thought to have died, and those who survived would find it extremely difficult to ever fully recover.
The dietary intake of people in affected areas was reduced from a healthy 2000 calories a day to a measly 580 – a quarter of the “normal” food intake. Unsurprisingly, without a balanced diet, children born to mothers who were pregnant during the famine showed a much lower than average birth weight.
But then something strange happened: their children’s children had the same low birth weight, despite their mother’s “normal” food and calorie intake.
On top of this, daughters of women exposed to the Dutch famine were twice as likely to develop schizophrenia than the usually calculated risk. So what was happening?
Welcome to epigenetics
We often talk about our genetic make-up and “how good” or “how healthy” our genes are. We also know “bad genes” can lead to us having a higher chance of developing a particular disease if our parents are carriers. But while scientists can look for those faulty or changed genes, over the last decade we have learned this is not the whole story.
Because it is not just our genes and DNA which determines our health, but also environmental factors such as diet, stresses, and lifestyle choices – just like in the Netherlands.
These environmental conditions, alongside the life experiences of our parents, grandparents, and even our great-grandparents, have been shown to flip “stop” and “go” signals which regulate pretty much every process taking place in our cells. These signals can then cause changes on top of the inherited DNA molecules which can determine our well being – hence the lower birth weight of babies only distantly related to the famine.
Epigenetics takes the age-old question of “nature vs nurture” to a whole new level of scientific interest. But it is a controversial field of study with wide-reaching implications which could change everything we thought we knew about genetic inheritance.
What we do know, though, is that the environment and our nutritional intake plays a crucial role in affecting changes to our DNA – which has been demonstrated by the effects of the Dutch famine. The famine has shown how changes in epigenetic markers – the “stop” and “go” signals – are inherited, from parent to offspring and to their offspring in turn. This process is called transgenerational inheritance.
The genes affected are ones that are important in processing nutrients and are associated with diseases such as diabetes or are implicated in mental health conditions such as schizophrenia and bipolar disorders.
Studies on identical twins show how the environment and trauma can change these epigenetic flags. While the siblings were genetically identical, their identical epigenetics changed over time – essentially showing how environmental factors can alter genes which are linked to depression, anxiety and obesity.
Recently, studies using mice, rats, fruit flies and worms have also shown that trauma and stress can affect these epigenetic flags which then get passed on to the next generation, and then on to the next.
We know that if a female rat takes good care of her offspring, for example, then the pups are able to cope better with stress compared to rat pups that were ignored and had high levels of stress. In this instance, the removal of “stop” signals on a specific gene seems to be linked to happier offspring.
Similarly, male mice who experience stress early in their lives pass this on, even to their grand pups – which are more likely to show symptoms of anxiety and depression, even if they were looked after well and grew up in a nurturing environment.
Fixing the future?
Studies in humans are difficult to control as generally we do not have a reference value for epigenetic markers before a trauma or stress, so we cannot make easy comparisons. But what we do know is that women who were pregnant while experiencing extremely stressful situations, such as the 9/11 attacks, apparently have passed on this experience to their child.
Their children have reported experiencing depression, anxiety and poor coping mechanisms in stressful situations. Similarly, children and grandchildren of Holocaust victims often have mental health issues.
But it isn’t all doom and gloom. We aren’t simply living at the mercy of our ancestors' past lives because we do know that at least some of the epigenetic marks are reversible.
We potentially can affect our epigenetics by living a healthy lifestyle and providing our body with the necessary building blocks for these epigenetic flags.
Recent research also shows that drugs can remove negative epigenetic marks and remove “stop” signals – which has been shown to allow changed genes present in cancer, Alzheimer’s or diabetes to go back to theie original state.
So while we may still be some way off fully understanding the role epigenetics plays in the “nature vs nurture” debate, one thing is clear: it’s not simply our genes that make us. So next time you’re feeling stressed or angry, or thinking about grabbing another takeaway pizza on the way home, think of your future grandchildren. It may save them a whole lot of bother.