Healthy Inspiration

Read: Being black in America can be hazardous to your health

In 2016, Rachel Yehuda of Mount Sinai hospital and her colleagues found that Holocaust survivors and their children both had evidence of methylation on a region of a gene associated with stress, suggesting that the survivors’ trauma was passed onto their offspring. The paper was criticized for, among other things, having a small sample size and not looking at the third and fourth generations of descendants of the Holocaust survivors.

The current Civil War paper overcomes some of these drawbacks, since it looked at thousands of veterans and their children. But the study examined only the statistics, not the genes themselves, so the idea that the connection is epigenetic is more like conjecture, or a process of elimination. The authors would have to follow the sample through further generations to know for sure.

And those are only some of the uncertainties when it comes to epigenetics. We don’t yet know, for example, which genes to look at for epigenetic changes. Or how epigenetic markers might survive the power-wash-like fertilization process. Confusingly, some studies have found that stressful times our grandparents experienced might actually be beneficial for future generations. One study found that people who were undernourished at age 9 had grandchildren with better mental health. Studies performed on a series of poor 19th-century harvests in Överkalix, Sweden, found that grandsons of men who had bountiful harvests during childhood actually died younger than expected, but granddaughters of women who were in the womb during a famine were also at a higher risk of death at a young age.

Lars Olov Bygren, the author of the Överkalix studies, told me this could be because it’s beneficial for our grandparents to have plenty of food before age 10, but after that age, something switches, and it’s in the best interest of our own longevity for them to be slightly undernourished. Jirtle, meanwhile, says that the contradictory findings show up because while too little food is bad, so is too much food. Ideally, our grandparents should be stressed just enough, but not too much.

In another twist, the Civil War paper shows that the sons could be protected from their fathers’ trauma if their mothers had good nutrition while they were pregnant, which is something that’s consistent with epigenetic research.

“By no means is it saying that whenever there’s trauma, that means it’s going to be transmitted,” Dora Costa, the lead author of the Civil War study and an economist at UCLA, told me. “The epigenetic story is optimistic because it allows for the possibility of reversibility through maternal nutrition.”

Jirtle, for example, has found that dietary supplements fed to a mother mouse were able to protect baby mice from exposure to a chemical called BPA. “As Hippocrates basically stated two millennia ago, food is medicine,” Jirtle told me.