Your sperm is as good as your father's diet, a new study suggests.
Researchers have known for some time that you are what your mother ate; that her – and her mother's diet – can trigger genes in the embryo and affect everything from whether you will be prone to overeating or becoming obese to your immunity.
Fathers, on the other hand, have been thought to pass on their genes and not much more.
However, researchers have now realised this is not the case. Far from it.
We each have about 25,000 genes – which contain information telling the body's cells what to do – but, not all our genes are active, or expressed, at any one time. Epigenetics (which means above the gene) is the study of changes in gene activity that can be inherited, but do not involve alterations to the genetic code. Epigenetics is the result of environmental and lifestyle factors – such as diet.
For the latest study, researchers from Monash University wanted to understand the transgenerational impact of a father's diet on their offspring's health outcomes – and specifically, in this case, future reproduction.
Susanne Zajitschek, one of the lead authors of the study, said the research was prompted by "curiosity about the potential of paternal nutrition to influence something as subtle as postcopulatory mechanisms – with the background that we knew already that nutrition can have profound transgenerational effects, as well as the fact that even social circumstances can alter a males' sperm traits".
She and her team experimented with male fruit flies, which share similar pathways and characteristics as human genes, putting them on either high- or low-protein diets.
"Our study found that males that were raised on either high- or low-protein diets, but spent their adulthood on an intermediate diet, produced sons that had large differences in gene expression, which most likely contributed to the resulting differences in sperm competitiveness," said Zajitschek, from the School of Biological Sciences.
"They differed in their ability to sire offspring, with the high-protein dads producing sons who were doing much better in sperm competition, which means their sperm was more likely to win against a competitor's sperm within the female tract.
"We also found that the immune response genes were less active in sons of low-protein fathers, while metabolic and reproductive processes were increased in sons of fathers on a high-protein diet."
How much can these findings be extrapolated to humans is unclear, Zajitschek said of the research published in the journal Biology Letters.
"However, it is already known that parental nutrition [pre-conception, both undernutrition and overnutrition] can have profound effects on offspring [for example disease and/or obesity susceptibility]," she told Fairfax Media. "It is hence at least theoretically possible that dietary transgenerational effects could also be observed in male fertility."
What can we take from it? That a healthy lifestyle is important for parents-to-be, both future mums and dads.
"Diet – or potentially a wide range of environmental factors – can have profound effects, even across generations, and long-term before having babies," Zajitschek said. "And it's not the mother's only, but dad's too."