Nutritional epigenetics: How your diet affects future generations

Over the past century, scientists’ view of genetics has changed dramatically.

Under the original model of genetics developed by biologist Gregor Mendel in 1865, genes - sections of DNA that largely determine our physical traits - were seen as fixed. In other words, they were believed to be mostly untouched by an individual’s environment.

The arrival of epigenetics as a field in 1942 overturned that assumption.

Epigenetics describes changes in gene expression that happen without altering the DNA sequence itself. Certain epigenetic changes are part of normal cellular processes, including those linked with ageing.

Yet environmental influences can also alter how genes function, which means human behaviours can affect genetics. Identical twins, for example, arise from one fertilised egg and therefore have identical genetic material. As they grow older, however, their physical appearance can diverge because they encounter different environmental conditions.

One twin might follow a nutritious, balanced diet while the other has an unhealthy diet. This can create differences in the expression of genes involved in obesity, helping the first twin maintain a lower percentage of body fat.

Some influences, including air quality, are largely beyond people’s control. Others are more manageable, such as physical activity, smoking, stress, drug use and exposure to pollutants from plastics, pesticides and fossil-fuel combustion, including vehicle exhaust emissions.

Diet is another influence, and it has led to the specialist area of nutritional epigenetics. The discipline centres on the ideas that “you are what you eat” - and “you are what your grandmother ate.”

Put simply, nutritional epigenetics examines how what you eat, along with the diets of your parents and grandparents, can influence your genes. Because dietary decisions made today may affect the genetics of a person’s future children, epigenetics could encourage healthier eating choices.

Two of us work in epigenetics, while the third investigates how dietary and lifestyle decisions can support good health. Our research group includes fathers, so studying this topic further strengthens our already personal understanding of parenthood’s transformative effect.

The Dutch Hunger Winter and nutritional epigenetics

The origins of nutritional epigenetics research can be linked to a devastating historical event: the Dutch Hunger Winter during the closing phase of World War II.

Under the Nazi occupation of the Netherlands, people had to survive on daily rations of 400 to 800 kilocalories - vastly below the 2,000-kilocalorie diet used as a benchmark by the Food and Drug Administration. Consequently, about 20,000 people died and 4.5 million experienced malnutrition.

Research showed that famine produced epigenetic changes in a growth- and development-related gene known as IGF2. These changes restricted muscle growth in both the children and grandchildren of pregnant women who lived through the famine. For later generations, this reduced growth was associated with a higher likelihood of obesity, heart disease, diabetes and low birth weight.

The results represented a turning point in epigenetics research. They clearly showed that environmental events such as famine can cause epigenetic changes in descendants, potentially with major consequences for health.

How a mother’s diet affects gene expression

Before this influential research, many scientists thought epigenetic changes could not be inherited across generations. Instead, they believed such changes resulted from exposures early in life, including during gestation, which is a particularly vulnerable developmental stage. Early nutritional epigenetics studies therefore concentrated on food intake during pregnancy.

Animal research subsequently supported the findings from the Dutch Hunger Winter. Such studies let researchers control animal breeding, helping them account for background variables. Rats and sheep, the animals used in this work, also reproduce faster than humans, enabling results to be obtained more quickly.

Researchers can additionally manage animals’ diets across their entire lives, making it possible to alter and assess particular dietary components. Taken together, these features make epigenetic changes easier to investigate in animals than in people.

In one experiment, scientists exposed pregnant female rats to vinclozolin, a widely used fungicide. The first generation born after exposure had a reduced capacity to produce sperm, resulting in greater male infertility. Importantly, as with the effects of famine, these consequences continued into later generations.

Although these studies were hugely important in establishing nutritional epigenetics, they overlooked other developmental stages and entirely ignored fathers’ contributions to their offspring’s epigenetic inheritance.

A more recent sheep study, however, found that a father’s diet, supplemented with the amino acid methionine from birth until weaning, influenced the growth and reproductive characteristics of the following three generations. Methionine is an essential amino acid that is involved in DNA methylation, which is one form of epigenetic change.

Healthier choices for future generations

Together, these studies highlight the long-lasting effect that parents’ diets can have on children and grandchildren. They may also strongly motivate prospective and current parents to make healthier dietary decisions, since parents’ food choices shape their children’s diets too.

Consulting a nutrition professional, such as a registered dietitian, can offer evidence-based guidance on practical dietary adjustments for individuals and families.

Much remains uncertain about the ways diet affects and influences genes. Even so, emerging nutritional epigenetics research provides a compelling and powerful case for considering lifestyle changes.

Researchers already understand much about the Western Diet, the pattern eaten by many Americans. A Western Diet contains high levels of saturated fat, sodium and added sugar, but little fibre. Unsurprisingly, Western diets are linked with adverse health outcomes including obesity, type 2 diabetes, cardiovascular disease and certain cancers.

A sensible first step is eating more whole, minimally processed foods - especially fruit, vegetables and whole grains - while reducing processed and convenience foods. These include fast food, crisps, biscuits and sweets, ready-to-cook meals, frozen pizzas, tinned soups and sweetened drinks.

The health advantages of these dietary shifts are well established, and they are outlined in the 2020–2025 Dietary Guidelines for Americans and by the American Heart Association.

For many people, adopting a different lifestyle is challenging, especially when food is involved. Motivation is crucial to making such changes. Fortunately, family and friends can help, as they have a powerful effect on lifestyle choices.

At a wider societal level, though, food security - people’s capacity to obtain and afford healthy food - should be an essential priority for governments, food producers and distributors, and non-profit organisations. Food insecurity is linked to epigenetic changes associated with poor health outcomes, including diabetes, obesity and depression.

Relatively straightforward lifestyle changes can have a substantial, measurable effect on the genes of people’s children and grandchildren. Therefore, when you decide against a bag of crisps and opt for fruit or vegetables instead, remember: It’s not just for you, but for the generations to come.

Nathaniel Johnson, Assistant Professor of Nutrition and Dietetics, University of North Dakota; Hasan Khatib, Associate Chair and Professor of Genetics and Epigenetics, University of Wisconsin-Madison, and Thomas D. Crenshaw, Professor of Animal and Dairy Sciences, University of Wisconsin-Madison

This article is republished from The Conversation under a Creative Commons licence. Read the original article.