In a lot of ways evolution has stacked the deck against those of us living in western society in the 21st century. Whereas a prehistoric forbearers benefited from a strong desire to eat as much fat and salt as they could get their hands on (because they frequently couldn’t get their hands on much) modern humans in developed nations can’t go 2 blocks without passing a burger joint or a pizzeria. When we give in to temptation a frequent excuse is “It’s not hurting anybody,” but recent research is beginning to show that that might not necessarily be true.

The Multi-Generational Mother

More and more, scientists are uncovering evidence that the struggles we face and the food we eat (or don’t eat) has an impact on the DNA of our offspring. It turns out that environmental factors like diet, exercise, and stress cause the body to alter the way DNA is expressed. Specifically, under certain conditions, the body produces methyl groups that stick to DNA like glue and block of certain segments, with important consequences on our bodies and behaviour.

One study in mice found that environmental factors alone can change parenting behaviour for multiple generations. You see, when mice are raising their young, some mothers are very nurturing and some are not. The most obvious way mouse mothers show their affection is by licking their offspring. Researchers found that when the offspring of nurturing and neglectful mothers were switched, the DNA of the baby mice was altered so that the infants who were licked the most were most likely to lick their offspring and the neglected mice turned into neglectful parents.

The Impact of Grandpa’s Diet

You might look at those results and say that the baby mice are just learning how to be parents based on what they see in the world, which is a fair point until you consider that similar effects have been observed in relation to obesity and lifespan. Those findings go beyond mice and extend to humans as well.

Researchers in Sweden looked at historical records for a small village north of the Arctic Circle were food availability was frequently not a guarantee. What they found was that the stress that a man was exposed to by living through a famine lead to genetic and health effects in not only his son, but his grandson as well.

If you need an example that is a little closer to home, scientists were recently able to identify a specific DNA signature in babies whose mothers were exposed to power outages during an ice storm in Quebec in 1998. Women who were pregnant during the ice storm and suffered power outages gave birth to babies with altered expression of genes linked to the immune system. The longer a woman was without power, the more pronounced the effect on the baby’s genes. This is the first study to show that objective environmental factors and not just emotional stress can have an effect on DNA.

If something as isolated as a power outage can have long term effects on genes related to the immune system, imagine the effects related to a high fat, high sugar diet spread over a lifetime. More research on mice has shown that obesity can be triggered by environmental factors and that those effects might last for generations. That is definitely something to consider next time you’re thinking of swinging by the drive-thru window.