Emotions and our susceptibility to disease can be altered by what our parents and grandparents ate and did in the past.

Scientists say our emotions and susceptibility to disease can be altered by what our parents and grandparents ate and did in the past.

The behaviour and experiences of our parents and grandparents can affect the traits they pass on to us, new research reveals.

A phenomenon called epigenetics shows how environmental influences can 'flick the switch' on genes that might otherwise remain switched off.

We inherit a set of genes but what we eat or experience can influence which of the genes are activated – and this can be passed on. 

We each have around 25,000 genes that contain information telling the body's cells what to do, but not all our genes are active at any one time. Epigenetics is the study of changes in gene activity that can be inherited, but that don’t involve changing the genetic code.

So while we might inherit a set of genes, what we eat or experience emotionally can influence which of those genes are activated. This biological imprint can be passed on to our children.

Studies increasingly show that nutrients, toxins and prenatal or postnatal environmental exposures can suppress or activate a gene. This can affect everything from our emotional wellbeing to our susceptibility to disease. For example, when certain genes are switched on, they can suppress cancer.

Around 10 years ago, a study of mice by Duke University found that “even subtle changes in maternal nutrition can dramatically change the coat colour of the offspring.” Changes to the mums’ diets also changed the babies’ susceptibility to diseases like obesity, diabetes, and cancer.

Scientists at The Victor Chang Institute in Sydney have now taken those findings a step further. In the study, the diet of the mother mouse determined whether a gene that controls the colour and likelihood of obesity, as well as its tendency to overeat, was switched on or off in the offspring.

"We've been giving [nutritional] supplements to [mice] mothers mid-gestation, when the ovaries and testes of the embryo are forming," says Dr Catherine Suter. "So we've been targeting the next generation. We found influences are stronger in the second generation than first – there's [some kind of] memory of what your mother or grandmother ate."

Dr Suter says the mice used in the study were genetically identical, so any changes in the offspring were simply the result of different diets.

"We've been working in this space for awhile now," she said. "We know that poor [maternal] nutrition can lead to early onset disease later in life [in the offspring].

"Now what's more pertinent is over-nutrition – something like one in three kids in primary school are overweight. There are inter-generational cycles of obesity – inherited complications – and it's not just about eating habits or whatever.

"What if you do eat well, [but] you have [weight] problems anyway?"

Epigenetics is helping to answer this question and helping scientists understand how to reverse the effects of previous generations' behaviour.

Unlike genes, which can take hundreds of years to change, epigenetic changes can occur relatively quickly.

"We don't need genetic change," Dr Suter says. "It takes one generation [of dietary change] to revert."

Environmental influences also play a part: studies have found that the offspring of stressed male rats had significantly higher levels of depression and anxiety, The Wall Street Journal reported. But maternal care could result in pups that were "essentially normal."

Scientists are still learning the rules of epigenetics and how to selectively target genes. But this all demonstrates how dynamic we are – we’re not just stuck with what we've been given.