How your life could change the cells of your grandkids

What you experience in your lifetime can modify your DNA, and these changes can be passed down through the generations.

We explain what the new science of epigenetics means for your children and grandchildren.

Everyone's heard of the genome: that double helix DNA code that is uniquely yours, unless you happen to have an identical twin. But there's another layer of complexity responsible for creating us — and that's the epigenome.

Your epigenome sits in your cells with your genome. It's a set of instructions that decides which bits of your DNA are activated, or which genes are switched on or off.

While every one of us has one unique DNA code, we all have many epigenomes because every different type of cell in the body — in your skin, fat, liver, and brain — has its own epigenome.

The science of epigenetics is just getting started, but promises to deliver big changes to the way we treat disease and understand heredity.

Making music with your DNA

If your DNA is the unique 'song of you', your epigenomes are the audio engineers that decide how that music will be played — which bits are loud, or edited out, whether the melody is dominant or maybe the drums are lost altogether.

Each of your audio engineers takes the same set of musical notes, but creates their own unique production. Similarly, in our bodies our epigenomes manipulate our DNA to create different types of cells.

Throughout your life, your DNA (the 'song of you') stays constant, but your epigenomes (the audio engineers) are more fluid — they change as we develop (such as during puberty) but also due to a host of other reasons that scientists are just starting to understand.

These epigenetic changes affect our cells and how they function and therefore the health of our bodies — both positively and negatively.

"It's very exciting," said Professor Anthony Hannan, head of the Epigenetics and Neural Plasticity Laboratory at the Florey Institute of Neuroscience and Mental Health.

"Epigenetics is a revolution that is going to transform medicine where the prevention and treatment of disease will be based on your genome and your epigenome, which is different for every set of cells or tissues in your body."

How can our lifestyles change our epigenome?

Epigenetic changes occur throughout our lives, in fact a degree of adaptability seems to be required for normal human health.

We know that smoking, alcohol consumption, diet, physical activity, obesity, psychological stress, trauma, physical stress, infectious diseases, environmental pollutants, sun exposure, working night shift and countless other environmental factors can change our epigenomes. We just don't know a lot of the details about how and to what extent.

"It's complicated, and we've only really in the last five years had the tools to be able to address the epigenome," said Professor Susan Clark, Head of Genomics and Epigenetics at the Garvan Institute of Medical Research.

Research into epigenetics is in its early days and understanding the impact of lifestyle factors on an individual's epigenome and health is tricky, mostly because it's difficult to run studies on humans for ethical reasons.

"The other challenge is that each person has one genome but multiple epigenomes, depending on the cell type. And as we age our epigenomes age, so it's an order of magnitude more complex."

How are epigenetic changes passed on?

One of the most interesting and controversial aspects of epigenetics is the concept of inheritance. This suggests that events in our lives can affect our children's development and health, and possibly our grandchildren's.

Similarly, experiences our parents and grandparents had before we were born may also impact on our lives.

"I think everyone's intrigued by this idea they're part of a history that isn't just about the genes that they have, their DNA, that it's also about the experiences that occurred before them to their ancestors. I think this is such a powerful idea," said Rachel Yehuda, Professor of Neuroscience and Psychiatry at the Mount Sinai School of Medicine, New York.

Professor Yehuda studies the impact of traumatic experiences on war veterans, survivors of the Holocaust, of the September 11 attacks and their children.

She's found that children born after the war to Holocaust survivors with post-traumatic stress disorder (PTSD) were more likely to develop PTSD or depression themselves, compared to other Jewish adults.

These children also shared epigenetic markers with their parents on a gene that made them more reactive to stress.

Hear more from Professor Yehuda in the Science Friction episode: 'The secrets inside your cells: epigenetics, trauma and our ancestral selves.'

Our understanding of how epigenetic changes could be transmitted from parent to child is still not entirely clear, but there is evidence to suggest this happens at the time of conception and during pregnancy.

How can mothers (and grandmothers) pass on epigenetic changes?

What a mother does while she is pregnant can impact on the epigenome of her developing baby.

And, because a female baby's lifetime supply of eggs is created when she's growing in her mother's womb, it can also impact on these eggs, and eventually the children they may become.

In this way, the activity of the pregnant mother can touch the lives of her grandchildren.

There's a very famous well-documented case where we can clearly see the impact of famine during pregnancy on a population over generations, Professor Clark said.

"In humans, the best example is during the WWII and the Dutch winter," she said.

During WWII, the Germans cut off food supplies to parts of the Netherlands causing a famine.

Professor Clark said babies born to women during this time had a lower birthweight. When those babies grew up and had their own babies, the third generation had significantly more problems with diabetes and obesity than the rest of the population.

Can fathers transfer epigenetic changes?

Fathers could transfer epigenetic changes to their children, and possibly grandchildren through changes to sperm around the time of conception, although most of our current evidence for this comes from studies in mice and rats.

Professor Hannan and his team at the Florey Institute have shown that stress affects the epigenome of mouse sperm — and this can have an impact for more than one generation.

"We showed that increased paternal stress hormone changed the epigenome of the sperm, and changed the offspring."

Physical stress in the father mice has been shown to increase anxiety in offspring, Professor Hannan said. But it's not all doom and gloom — increased physical activity in the father mice has positive effects too.

Can you heal your life (and those of your children and grandkids) through epigenetics?

Sort of. Professor Clark says while we can't change our DNA sequence, we can change our epigenome, pointing out that this is already happening in some areas of cancer treatment.

"There's epigenetic therapy drugs that are being used in cancer that basically remodel your epigenome," she said.

"There's lots of potential, it's an incredibly exciting area.

"But we need to understand a lot more about the building blocks and the functional consequences of what makes up the epigenome and how lifestyle and environment impacts on the epigenome."

And until we know more, following a healthy lifestyle and doing the things we know have a positive impact on your health — such as eating a good diet, avoiding alcohol, doing exercise; and keeping stress to a minimum — is a good idea.

So for now, eat your broccoli and watch this space!