Being dad is a hefty responsibility. It’s a never-ending job, for sure. Each and every choice we make in real time affects and, more accurately, shapes our children’s experience of the world. However, there’s another level of influence, including our past experiences — not to mention those of our parents, and grandparents, that also weigh heavily on our future generations.
Where our ancestors lived, as well as their habits, values, morals, etc., clearly have effects that we pass down through the generations. But what can we say about the legacy of their health status? Did our ancestors smoke, drink or take drugs; did they endure famine or poverty, or fight in a war?
Not just a sperm donor
It’s no great shock that expectant mothers have to pay attention to their lifestyle, environment and stress level. Yet, an expectant father’s lifestyle and environment also equally influence the lives of his children and grandchildren. In makes complete sense, of course, that a mother’s environment during reproduction would influence her children. However, the father’s pre-conception environment plays an equally important role.
I was thinking back to a now well-known Emory University study that looked at how fear, when associated with a particular smell, affected male mice and, most significantly, how that association left an imprint on -their descendants’ brains. In the study, researchers exposed the mice to acetophenone — a sweet, almond-like smelling ketone (chemical) used in soaps and perfumes, as a flavoring agent in foods, and as a plastics and resins thinner — and then gave them a mild foot shock. After being exposed to this treatment five times a day for three days, the mice became predictably fearful of the odor, freezing in the presence of acetophenone, even when they didn’t receive a shock.
The mice’s children also were sensitive to the smell of acetophenone, especially when compared with other odors, and more likely to be startled by an unexpected noise while being exposed to the smell. As tellingly, the grandchildren of these mice were anxious in the presence of acetophenone. The researchers also found that the brains of all three generations had undergone significant rewiring, making them more sensitive to smell of acetophenone. The researchers even ran vitro fertilization experiments to make sure that the father was not in some way passing on a fear of acetophenone through interactions with the mother. What they found was an epigenetic tweak in the sperm of these mice that continued in the offspring’s DNA, leading to increased receptor expression in the animals’ noses and, ultimately, enhanced sensitivity to acetophenone.
This hereditary transmission of the mice’s environmental information can be explained by “epigenetics,”—chemical changes to the genome that affect how DNA is packaged and expressed without altering its structure. Epigenetic changes are known to greatly affect fetal development, but were thought to be “wiped clean” before birth. However, recent research has shown that some of these markers, or “epigenetic signatures,” survive all the way from the sperm cell, throughout fetal development, and persist in the baby.
Epigenetic heritability, which accounts for trait such as weight, height, disease susceptibility, and intelligence, isn’t a new phenomenon; it’s been observed for years in plants.
Tomatoes, as an example, pass along chemical markings that control an important ripening gene. But, we now have significant evidence that this phenomenon occurs in rodents and humans as well.
Though the mechanisms by which epigenetic inheritance works are still not fully understood, it’s increasing clear that sperm gain and lose epigenetic marks. Epigenetics started drawing the attention of scientists in the early 2000s, when scientists noticed that environmental factors could influence the addition or removal of chemical tags on DNA that turn genes on and off. We know, as an example that mom can—and often does—pass on environmental exposures, and habits such as a poor diet, to her fetus during pregnancy. Prolonged exposure to chemical, physical or emotional elements in an expectant mother can wreak havoc on a baby’s budding nervous system. In one study,
pregnant rats exposed to pesticides and fungicides gave birth to organ-damaged offspring. What was so fascinating about this study, however, was that the sperm of mom’s male offspring showed changes in DNA methylation—an epigenetic mechanism used by cells to control gene expression—that persisted for several generations. So these
future “dads” were about to pass on these changes to their offspring.
A 2005 British study found that dads who started smoking before the age of 11, which is pretty damn early, were at increased risk of having fat boys. A study of Swedish historical records showed that men who had experienced famine before puberty were less likely to have grandsons with heart disease or diabetes than men who had plenty
Acknowledging dad’s role
The thing to acknowledge here is that expectant dads mold their kids, too. Indeed, a dad’s health has a measurable impact on his future offspring’s health and happiness. Even if the dad has “bad” genes (those that predispose him to cancer, or heart disease) so to speak, his offspring’s overall health will be a culmination of his choices, habits, and
exposures, as well as those of his ancestors. Really, this “discovery” is old hat to many of us. I’ve been telling my male patients for years that excess weight, unhealthy lifestyle habits like smoking, and exposure to environmental toxins adversely impacts their sperm quality. Environmental toxins, in particular, leave their mark on our successors. Vinclozin, a fungicide once liberally sprayed on crops, is a known endocrine disrupter that blocks the production of testosterone. In one study, male rats whose mothers receive a dose of vinclozin late in their pregnancy are highly likely to be born with defective testicles and reduced fertility, and these problems persisted for a minimum of four subsequent generations of male rats.
Creating fatherly awareness
We need to let our male patients know that the health of their unborn children can be affected by what and how much men eat; the toxins they absorb; the traumas they endure; their socioeconomic status; and even their age at the time of conception. A man’s life experience leaves biological traces on his children, which they certainly pass along
to future generations. I always remind patients of the three main factors that can switch our genes on or off. They include what we ingest (food, drink, air, toxins); what we experience (stress, trauma); and how long, and well, we live. We should never forget that our children are shaped in everyway by the life we lead and the world we live in.