Over the past century, researchers’ understanding of genetics has undergone a profound transformation.
Genes, regions of DNA largely responsible for our physical characteristics, were considered immutable in the original genetics model developed by biologist Gregor Mendel in 1865. That is, genes were thought to be largely unaffected by a person’s environment.
The emergence of the field of epigenetics in 1942 destroyed this idea.
Epigenetics refers to shifts in gene expression that occur without changes in the DNA sequence. Some epigenetic changes are an aspect of cell function, such as changes associated with aging.
However, environmental factors also influence the functions of genes, meaning that people’s behavior influences their genetics. For example, identical twins develop from one fertilized egg and as a result share the same genetic makeup. However, as the twins grow older, their appearance may differ due to different environmental exposures. One twin may eat a healthy, balanced diet while the other eats an unhealthy diet, resulting in differences in the expression of their genes that play a role in obesity, causing the former twin to have a lower body fat percentage.
People don’t have much control over some of these factors, such as air quality. However, other factors are more within our control: physical activity, smoking, stress, drug use and exposure to pollution, such as that from plastics, pesticides and the combustion of fossil fuels, including car exhaust.
Another factor is nutrition, from which the subfield of nutritional epigenetics emerged. This discipline deals with the notions that ‘you are what you eat’ – and ‘you are what your grandmother ate’. Basically, nutritional epigenetics is the study of how your diet, and the diet of your parents and grandparents, affects your genes. Because the nutritional choices a person makes today influence the genetics of their future children, epigenetics can provide motivation for making better nutritional choices.
Two of us work in the field of epigenetics. The other explores how diet and lifestyle choices can help people stay healthy. Our research team includes fathers, so our work in this area only increases our already intimate familiarity with the transformative power of parenting.
A story of famine
The roots of nutritional epigenetics research can be traced back to a moving chapter in history: the Dutch Hunger Winter in the final phase of the Second World War.
During the Nazi occupation of the Netherlands, the population was forced to live on rations of 400 to 800 kilocalories per day, which is in stark contrast to the typical 2,000 kilocalorie diet used as a standard by the Food and Drug Administration. As a result, approximately 20,000 people died and 4.5 million people became malnourished.
Research has shown that the famine caused epigenic changes in a gene called IGF2, which is linked to growth and development. These changes suppressed muscle growth in both the children and grandchildren of pregnant women who had endured the famine. For these subsequent generations, that oppression led to an increased risk of obesity, heart disease, diabetes and low birth weight.
These findings marked a pivotal moment in epigenetics research – clearly demonstrating that environmental factors, such as famine, can lead to epigenetic changes in offspring that can have serious consequences for their health.
The role of the mother’s diet
Until this groundbreaking work, most researchers believed that epigenetic changes could not be passed from one generation to the next. Rather, researchers thought that epigenetic changes might occur with exposure in early life, such as during pregnancy – a very vulnerable period of development. The first epigenetic nutritional research therefore focused on dietary intake during pregnancy.
The findings from the Dutch Hunger Winter were later supported by animal studies, allowing researchers to determine how animals are bred, which can help control for background variables. Another benefit for researchers is that the rats and sheep used in these studies reproduce faster than humans, allowing for faster results. In addition, researchers can fully monitor the diet of animals throughout their lives, allowing specific aspects of diet to be manipulated and investigated. Together, these factors allow researchers to better investigate epigenetic changes in animals than in humans.
In one study, researchers exposed pregnant female rats to a common fungicide called vinclozolin. In response to this exposure, the first born generation showed a reduced ability to produce sperm, leading to increased male infertility. Crucially, these effects, like those of the famine, were passed on to subsequent generations.
As monumental as these works are in shaping nutritional epigenetics, they ignored other developmental periods and completely ignored the role of fathers in the epigenetic inheritance of their offspring. However, a more recent study in sheep found that a paternal diet supplemented with the amino acid methionine given from birth to weaning affected the growth and reproductive traits of the next three generations. Methionine is an essential amino acid involved in DNA methylation, an example of an epigenetic change.
Healthy choices for future generations
These studies underline the lasting impact that parents’ diets have on their children and grandchildren. They also serve as a powerful motivator for parents-to-be and current parents to make healthier food choices, as the food choices parents make influence their children’s diets.
Meeting with a nutrition professional, such as a registered dietitian, can provide evidence-based recommendations for making practical dietary changes for individuals and families.
There are still many unknowns about how diet impacts and affects our genes. What research is beginning to show about nutritional epigenetics is a powerful and compelling reason to consider lifestyle changes.
There are many things researchers already know about the Western diet, which is what many Americans eat. A Western diet is high in saturated fats, sodium and added sugars, but low in fiber; Not surprisingly, Western diets have been linked to negative health outcomes, such as obesity, type 2 diabetes, cardiovascular disease and some cancers.
A good start is to eat more whole, unprocessed foods, especially fruits, vegetables and whole grains, and fewer processed or convenience foods – such as fast food, chips, cookies and sweets, prepared meals, frozen pizzas, canned soups and sweetened drinks.
These dietary changes are known for their health benefits and are outlined in the Dietary Guidelines for Americans 2020-2025 and by the American Heart Association.
Many people find it difficult to embrace a lifestyle change, especially when it comes to food. Motivation is a key factor in making these changes. Fortunately, family and friends can help here: they have a major influence on lifestyle decisions.
At a broader, societal level, food security—that is, people’s ability to access and afford healthy food—should be a critical priority for governments, food producers and distributors, and nonprofit organizations. Lack of food security is associated with epigenetic changes that have been linked to negative health outcomes such as diabetes, obesity and depression.
Through relatively simple lifestyle changes, people can significantly and measurably influence the genes of their children and grandchildren. So when you pass up a bag of chips – and choose fruit or vegetables instead – remember: it’s not just for you, but for generations to come.
This article is republished from The Conversation, an independent nonprofit organization providing facts and analysis to help you understand our complex world.
It was written by: Nathaniel Johnson, University of North Dakota; Hasan Khatib, University of Wisconsin-Madisonand Thomas D. Crenshaw, University of Wisconsin-Madison.
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Nathaniel Johnson receives funding from the U.S. Department of Agriculture and the National Institutes of Health. He has previously received funding through the National Science Foundation, the National Cattlemen’s Beef Association and the North Dakota Beef Checkoff.
Hasan Khatib receives Funding No. 2023-67015-39527 from the USDA National Institute of Food and Agriculture
Thomas D Crenshaw receives funding from Hatch Multi-State Research Formula Funds; USDA/National. Institute of Food and Agriculture; DHHS, PHS, National Institutes of Health.