Epigenetics – is nature or nurture most powerful?

Did you know that human DNA is not static and can be heavily affected by environmental factors? Here, we investigate how nature and nurture interact dynamically to influence health outcomes.

Harvard University’s Centre on the Developing Child explains epigenetics as “an emerging area of scientific research that shows how environmental influences can affect gene expression.” Gene expression is the process by which the information encoded in a gene is turned into a function.

The Centre’s ongoing research, and that of other experts in the field, has overturned the notion that an individual’s genetic make-up is set in stone.

In fact, our genes are now understood to accumulate chemical marks over time, depending on what we experience – which then determine how much of our genetic makeup is expressed later in life.

A typical example can be seen in two children with similar – or even identical – genetic make-up (such as siblings or twins), who manifest different behavioural patterns, health characteristics, and achievements.

This collection of chemical marks, or modifications to DNA and DNA-associated proteins in a cell, is called the “epigenome”. While these marks can be passed down from cell to cell, and from one generation to the next, environmental factors, such as diet, climate, smoking, alcohol consumption, toxin exposure, physical activity, and stress levels, are critical in determining whether a particular disease develops or not.

For clarity, the National Human Genome Research Institute in the USA defines the term epigenome as a series of “chemical compounds that modify, or mark, the genome in a way that tells it what to do, where to do it, and when to do it,” even though these marks are not part of the DNA itself.

Lining up the pressing questions

An important consideration for researchers, and those of us intent on maintaining optimal health, is whether an incredibly nurturing childhood or a career filled with excruciating levels of stress will have the greatest impact on our genetic make-up. Is the positive influence, or potential damage, temporary or permanent; and to what extent can a negative influence, such as smoking, be reversed to restore optimum health if we quit?

Associate Professor Allan McRae at the University of Queensland reports that genes can play a major role in some traits. For example, genes influence height by up to 80%, whereas our environment accounts for only 20%. He says, “The epigenome gives interesting insights into environmental influences, as the inherited epigenome tends to get reset at conception, and changes with age, exposure, and disease – meaning we can study how it has changed over time.”

This brings us to a few of the key questions researchers are looking to answer:

• Is methylation (a process in which a gene gets turned on or off) a cause, or a consequence, of neurodegenerative diseases (for example, Parkinson’s disease) or chronic mental health conditions (for example, schizophrenia)?

• To what extent can giving up smoking and reducing stress levels lower our ‘methylation age’, delaying the onset of illness or preventing it altogether?

The Centre on the Developing Child suggests that high-quality healthcare for pregnant women across societal demographics, along with nurturing childcare and rich learning experiences for the very young, are the most important steps in building epigenetic resilience.

Experiences during early, rapid brain development appear to have the greatest impact on our future capacity for health maintenance.

A local genetics expert weighs in

“The interplay between nature and nurture, emphasising how environmental factors can shape gene expression through epigenetics, is fascinating” says Dr René Goliath, a medical biological scientist who offers genetic counselling. “We now know that lifestyle can radically influence our long-term health by modifying the epigenome.”

One particularly intriguing aspect of epigenetics, according to Dr Goliath, is evidence from animal studies suggesting some changes can be passed down to offspring in a process called “transgenerational epigenetic inheritance.” However, the exact mechanism and extent of this in humans is still being studied.

“So, while the epigenome is largely reset at conception, certain chemical modifications may persist across generations influencing disease risk in future generations. This knowledge reinforces the importance of creating healthy environments, particularly in early childhood when epigenetic programming is being established. It also offers hope that positive changes, even later in life, can reshape our health trajectory and potentially benefit future generations.”