March 4th, 2019 

Now that we have set the table for health with optimal delivery and newborn feeding methods, we need to look at the issues of nature versus nurture.

The theory of nature versus nurture is that your genes, your environment or both have a profound impact on human health. Essentially, is it your genetic code that dictates your health outcome or is it your parents nurturing nature of you? My favorite researchers in this space are Dr. Moshe Szyf and Dr. Michael Meaney at McGill University.

They performed some of the seminal research in rodents looking to prove this answer. From his epigenetic explanatory article, "We propose that the modulation of DNA methylation in response to environmental cues early in life serves as a mechanism of life-long genome "adaptation" that molecularly embeds the early experiences of a child ("nurture") in the genome ("nature"). (Szyf 2011)

What he is saying is that the changes to your child's gene's DNA sticky notes that say read or do not read me in response to the environmental cues like parenting can have a life-long effect on your child's genome or book of life. This in turn sets the stage for how a child may respond to the environment later on, good or bad.

Unfortunately, it turns out that if these environmental cues are negative, they can place dysfunctional sticky notes on a child's genes that can be conserved over future generations. I believe that this may be the reason that we are seeing such a steep climb in the incidence of many diseases in children.

Let us look at some of the research to gain a better understanding. In the hallmark research by Moshe Szyf, he looked at the response of rat offspring to differential social grooming and subsequent stress responses over time. His group cross fostered rat pups born to a high licking and grooming (HLG) mother subsequently given to a low licking and grooming (LLG) mother to raise/nurture and visa versa. Animals that were poorly groomed by a LLG mother rat despite having the genes of a HLG mother had higher long-term stress responses because of brain stress receptor changes that occurred. This study showed that a baby is primed epigenetically to expect a tough world if his mother was not a loving groomer. Conversely, the HLG groomed offspring had reduced receptors for stress expecting a happier world. (Szyf et. al. 2007)

The real proof of the study was noted when these animals had much different responses to the same stressors later in life. Poorly nurtured rat pups had more stressful responses to the same stimulus compared to highly groomed pups.

At the simplest level, this research shows us that a baby can develop a heightened stress response later in life. Evolutionarily, this makes complete sense to me. If a baby perceives that a stressful world exists then her stress related genes will be turned on in anticipation of continued issues requiring certain stress receptors to be highly functional.

This is likely the intuitive reason that certain cultures shielded their women and children from external stressors during pregnancy and early childhood.

Dr. Romen and colleagues persisted in this line of research in humans and found similar results with alterations in the stress glucocorticoid receptor of children exposed to physical abuse. The stress receptor gene sets in children exposed to physical abuse had increased epigenetic methylation "sticky notes" that down-regulates the gene and up-regulates the child's stress response. (Romen et. al. 2014)

On another line of epigenetic/genetic thinking, Dr. Mitchell looked at telomere length in children after the death or loss of a father, a severe stressor. Their group found a 14% reduction in telomere length in the father loss group. Telomere tails protect the DNA code from damage and are highly associated with longevity. This is profound as telomere length shortening causes significant issues with social and physically negative outcomes. (Mitchell et. al. 2017)

Confounding this research even further, Dr. Slavich and colleague looked at the perceived response to stress in humans and the gene response. What they found is even more disturbing! Your perception of an event has the ability to alter gene expression further. This may explain the differential response of a group of soldiers being exposed to a road side bomb and one has post traumatic stress disorder where the other survivors do not. (Slavich et. al. 2013)

I could go on and on with the emerging research that continues to prove this reality of environment and gene interactions profoundly affecting our children, however, that would belabor the point. The better path now is to think of how to alter this effect.

Ideally, we would like to shelter our mother-child dyad from all significant stressors during pregnancy and childhood until they are significantly older and their genes are well established and running full steam ahead. Clearly this is polyannish as life happens to us and often not by choice. That being said, we have the ability to make and take a choice and to learn how to perceive events in a positive light.

How can we see an event in a positive light? How do we choose this route?


Dr. M

Szyf Epigenetic Article
Szyf Environ Mol Mutagen Article
Szyf Reproductive Toxicol Article
Mitchell Pediatrics Article
Romens Child Development Article
Slavich Clinical Psych Science Article
Weaver Epigenetics Article