What Is Epigenetics

Written by Dr. Steve Chaney on . Posted in current health articles, Food and Health, Nutritiion, Obesity

Can What We Eat Affect Our Kids?

Author: Dr. Stephen Chaney

 

what is epigeneticsWhat is epigenetics?  For me, the first stages of understanding came a while back.  When I was a young graduate student (which is more than just a few years ago), I was taught that all genetic information resided in our DNA. During conception, we picked up some DNA from our dad and some from our mom, and that DNA was what made us a unique individual.

We knew that environmental influences such as diet, lifestyle and exposure to toxic chemicals could affect our health personally. However, we never dreamed that the effects of those environmental influences could actually alter our gene expression, and that those genetic alterations could be passed on to our children.

Today we know that environmental influences can actually modify our DNA and that those modifications can be passed on to our offspring – a process called epigenetics.

What Is Epigenetics & How Does It Affect Gene Expression?

Simply put, epigenetics involves modifications to our DNA. DNA can be methylated or acetylated and the proteins that bind to our DNA can be modified in multiple ways. That is important for two reasons:

  • These alterations can turn genes on and off. That means that epigenetic modifications can alter gene expression.
  • These alterations can be influenced by our environment – diet, lifestyle, and exposure to environmental chemicals

In a previous “Health Tips From the Professor” article titled “Can Diet Alter Your Genetic Destiny?”  I discussed recent research suggesting that a healthy diet and lifestyle causes epigenetic changes in the DNA that may reduce your risk of heart disease, cancer and diabetes.

That alone was a monumental discovery. Even more monumental is the recent discovery that at least some of those epigenetic changes can be passed on to our children, which brings me to the question I posed in the title of this article: “Can what we eat affect our kids?”

Animal Studies Showing That Epigenetic Changes Can Be Inherited

epigenetic changes are inheritedAs is often the case, the first definitive study showed that epigenetic changes were heritable was an animal study. This study was done with a mouse strain called agouti (Waterman and Jirtle, Mol. Cell. Biol. 23: 5193 – 5300, 2003). Agouti mice can have two remarkably distinctive phenotypes. They can either have a yellow coat, become obese as adults and be prone to cancer and diabetes as they age or they can have a brown coat and grow up to be lean and healthy.

It had been known for some time that these phenotypic differences were controlled by the epigenetic methylation of a specific gene called the agouti gene. The agouti gene codes for a genetic regulator that controls coat color, feeding behavior, and body weight set-point, among other things. When the agouti gene is under methylated it is active. As a consequence the mice have yellow coats and are prone to obesity. When the agouti gene is highly methylated it is inactive. The mice have brown coats and are lean and healthy.

Moreover, methylation of the agouti gene is not a purely random event. Mothers with the yellow, obese phenotype tended to produce a preponderance of offspring with the same phenotype and vice-versa. In short, the epigenetic methylation pattern of the agouti gene could be passed from generation to generation. It was heritable.

Waterman and Jirtle’s research broke new ground by showing that the methylation of the agouti gene could be strongly influenced by what the mother ate while the fetal mice were still in the womb.

When they fed agouti mothers a diet with extra folic acid, B12, betaine and choline (all nutrients that favor DNA methylation) during conception and pregnancy the agouti gene of their offspring became highly methylated. A high percentage of those offspring had brown coats and grew up to be lean and healthy.

However, when Waterman and Jirtle put agouti mothers on a diet that was deficient in folic acid, B12, betaine and choline during conception and pregnancy the agouti gene of their offspring was under methylated. Many of those offspring had yellow coats and grew up to be fat and unhealthy.

Subsequent studies from the same laboratory have shown that:

  • Addition of genistein, a phytonutrient from soy, to the maternal diet also favors methylation of the agouti gene and protects against obesity in agouti mice (Dolinoy et al, Environmental Health Perspective, 114: 567-572, 2006).
  • The addition of the environmental toxin bisphenol A to maternal diets causes under methylation of the agouti gene and predisposes to obesity in agouti mice, but this effect can be reversed by also feeding the mother genistein or folic acid and related nutrients during pregnancy (Dolinoy et al, PNAS, 13056-13061, 2007).

The agouti mice studies provide a dramatic example of how diet and environmental exposure during pregnancy can cause epigenetic changes in fetal DNA that have long term health consequences for the offspring. However, they are animal studies. Does the same hold true for humans?

Diet, Epigenetic Changes, and Obesity in Humans

diet-epigenetic-changes-obesityWith humans, it is really difficult to determine whether epigenetic changes that occur during conception and pregnancy affect our children. That is because when you measure an epigenetic effect in a child or adult, it is difficult to sort out how much of that effect was caused by what the mom ate during pregnancy and how much was caused by how the family ate as the kids were growing up.

Unfortunately, there is a tragic human experiment that shows that the same kind of epigenetic changes are heritable in humans. I’m referring to what is known as the “Dutch Hunger Winter”. This was a period of starvation during 1944-1945, the final year of World War II, when the Germans set up a blockade that prevented food from reaching western Holland. During that few months even pregnant women were forced to live on food rations providing a little as 500 calories a day.

This was an event without parallel in human history. Holland is not a third world country. Once the blockade was lifted children born during the Hunger Winter had the same plentiful supply of food as every other Dutch citizen. This has allowed generations of research scientists to ask what were the effects of a brief exposure to malnutrition during conception and pregnancy.

The health consequences were dramatic. 50 years later individuals who were conceived during the Hunger Winter weighed about 14 pounds more, had waists about 1.5 “ larger, and were three times more likely to have heart disease than those born to mothers who were in their second or third trimester of pregnancy during that time. By the time they reached age 63, they experienced a 10% increase in mortality.

What caused those health consequences? Could the cause have been epigenetic? Recent research suggests that the answer might be yes.

A recent study analyzed epigenetic changes in DNA from blood samples of survivors born during the Hunger Winter that had been collected when they were 59 years old (Tobi et al, Int. J. Epidemiology, doi: 10.1093/ije/dyv043, 2015). This study showed:

  • A distinct pattern of DNA methylation was observed in survivors who were conceived during the Hunger Winter. This pattern of DNA methylation was not observed in survivors who were in their second or third trimester during the Hunger Winter. It was also not seen in people who were conceived immediately before or after the Hunger Winter.
  • Some of the genes with distinctive methylation patterns were genes that affected things like cholesterol levels and insulin sensitivity, which have the potential to increase disease risk.
  • Other genes with distinctive methylation patterns were genes that affected metabolism. They were “thrifty” genes that increased the efficiency of metabolism. Increased efficiency of metabolism is beneficial when calories are scarce, but can lead to obesity when calories are plentiful.

That is a truly remarkable finding when you think about it. If these data are true, they suggest that starvation during early pregnancy caused the fetus to make epigenetic changes to its DNA that allowed it to become more efficient at energy utilization, and those epigenetic changes have lasted a lifetime – even when food was abundant throughout the rest of that lifetime.

What Is Epigenetics And Can What We Eat Affect Our Kids?

can what we eat affect our kidsThe studies I featured in this article are powerful “proof of concept” that diet and environmental exposure during conception and pregnancy can result in epigenetic changes to the DNA of the offspring that can persist throughout their life and dramatically affect their health. However, it is not yet clear how they apply to you and me.

  • Agouti mice are a very special strain of mice. It is not yet clear what effect folic acid, genistein and bisphenol A have on epigenetic modification of specific human genes, and whether those epigenetic modifications will have health consequences in humans.
  • The specific circumstances of the Dutch Hunger Winter are unlikely to be repeated on any significant scale. The closest approximation I can envision would be a woman who becomes pregnant while on a very low calorie fad diet.

There are, of course, many other examples of heritable epigenetic modifications. For example:

  • When female rats are maintained on a “junk-food diet” high in fat and sugar during pregnancy and lactation their offspring show a marked preference for high fat foods (Ong & Muhlhausler, FASB J, 25: 2167-2179, 2011). They also show epigenetic alterations of the central reward pathways that may pre-condition them to require higher intakes of fat to experience pleasure from eating.
  • When rats are fed diets deficient in omega-3 fatty acids, adolescent rats from the second and subsequent generations display marked increases in hyperactivity and anxiety (For more details, see my “Health Tips from the Professor” article titled “The Seventh Generation Revisited”.
  • In a clinical trial of 162 obese Canadian mothers who had children before and after weight loss surgery, the children born after weight loss surgery were half as likely to grow up overweight or obese as the children born before the weight loss surgery (Smith et al, Journal of Clinical Endocrinology & Metabolism 94: 4275-4283, 2009), and this correlated with epigenetic modification of genes that play a role in obesity, diabetes, cancer and heart disease (Guernard et al, PNAS 110: 11439-11443, 2013).

Taken together, the existing data suggest that our diet and environmental exposure during conception and pregnancy can cause epigenetic changes to our children’s DNA that may affect their future health in ways that we can only begin to understand at present. It is a sobering thought.

 

The Bottom Line

 

  • The term epigenetics describes modifications to our DNA that turn our genes off and on.
  • In this article I discussed two powerful “proof of concept” studies, one in rats and the other in humans, showing that diet and environmental exposure during conception and pregnancy can result in epigenetic changes to the DNA of the offspring that can persist throughout their life and dramatically affect their health.
  • The health consequences of these epigenetic modifications include obesity, diabetes, cancer, heart disease, hyperactivity, anxiety and many more.
  • This is a new paradigm. Most prenatal nutrition advice is currently based on what it takes to have a healthy baby – not on what it might take for your child to experience better health throughout their life.
  • Of course, the science of epigenetics is relatively new. It will be many years before we will be able to make specific recommendations as to what your diet should be like during pregnancy and lactation if you wish to make beneficial modifications to your baby’s DNA.
  • However, you should be aware that what you eat during pregnancy & lactation may influence the health of your children – not just at the time of their birth – but throughout their life, and that a high calorie, “junk-food” diet or a fad weight loss diet just may not be your best choice.

*The agouti mice picture is by Randy Jirtle and Dana Dolinoy (E-mailed by author) [CC BY 3.0 (http://creativecommons.org/licenses/by/3.0)], via Wikimedia Commons.

 

These statements have not been evaluated by the Food and Drug Administration. This information is not intended to diagnose, treat, cure or prevent any disease.

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Comments (1)

  • Mary Butler

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    I have long wondered why a beautiful, gifted mom and wife of 5 gifted children, is morbidly obese. She is in her 40’s and struggling for life from cancer. Doctors have given up on her…..so very tragic! This may be the answer, her mom is also morbidly obese. Her one sibling is moderately overweight. Thank you for all you do.

    Reply

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Latest Article

Can Plant-based Diets Be Unhealthy?

Posted September 10, 2019 by Dr. Steve Chaney

Do Plant-Based Diets Reduce Heart Disease Deaths?

Author: Dr. Stephen Chaney

 

plant-based diets vegetablesPlant-based diets have become the “Golden Boys” of the diet world. They are the diets most often recommended by knowledgeable health and nutrition professionals. I’m not talking about all the “Dr. Strangeloves” who pitch weird diets in books and the internet. I am talking legitimate experts who have spent their life studying the impact of nutrition on our health.

Certainly, there is an overwhelming body of evidence supporting the claim that plant-based diets are healthy. Going on a plant-based diet can help you lower blood pressure, inflammation, cholesterol and triglycerides. People who consume a plant-based diet for a lifetime weigh less and have decreased risk of heart disease, diabetes, and cancer.

But, can a plant-based diet be unhealthy? Some people consider a plant-based diet to simply be the absence of meat and other animal foods. Is just replacing animal foods with plant-based foods enough to make a diet healthy?

Maybe not. After all, sugar and white flour are plant-based food ingredients. Fake meats of all kinds abound in our grocery stores. Some are very wholesome, but others are little more than vegetarian junk food. If you replace animal foods with plant-based sweets, desserts, and junk food, is your diet really healthier?

While the answer to that question seems obvious, very few studies have asked that question. Most studies on the benefits of plant-based diets have compared population groups that eat a strictly plant-based diet (Seventh-Day Adventists, vegans, or vegetarians) with the general public. They have not looked at variations in plant food consumption within the general public. Nor have they compared people who consume healthy and unhealthy plant foods.

This study (H Kim et al, Journal of the American Heart Association, 8:e012865, 2019) was designed to fill that void.

 

How Was The Study Done?

plant-based diets studyThis study used data collected from 12,168 middle aged adults in the ARIC (Atherosclerosis Risk in Communities) study between 1987 and 2016.

The participant’s usual intake of foods and beverages was assessed by trained interviewers using a food frequency questionnaire at the time of entry into the study and again 6 years later.

Participants were asked to indicate the frequency with which they consumed 66 foods and beverages of a defined serving size in the previous year. Visual guides were provided to help participants estimate portion sizes.

The participant’s adherence to a plant-based diet was assessed using four different well-established plant-based diet scores. For the sake of simplicity, I will include 3 of them in this review.

  • The PDI (Plant-Based Diet Index) categorizes foods as either plant foods or animal foods. A high PDI score means that the participant’s diet contains more plant foods than animal foods. A low PDI score means the participant’s diet contains more animal foods than plant foods.
  • The hPDI (healthy plant-based diet index) is based on the PDI but emphasizes “healthy” plant foods. A high hPDI score means that the participant’s diet is high in healthy plant foods (whole grains, fruits, vegetables, nuts, legumes, coffee and tea) and low in animal foods.
  • The uPDI (unhealthy plant-based diet index) is based on the PDI but emphasizes “unhealthy” plant foods. A high uPDI score means that the participant’s diet is high in unhealthy plant foods (refined grains, fruit juices, French fries and chips, sugar sweetened and artificially sweetened beverages, sweets and desserts) and low in animal foods.

For statistical analysis the scores from the various plant-based diet indices were divided into 5 equal groups. In each case, the group with the highest score consumed the most plant foods and least animal foods. The group with the lowest score consumed the least plant foods and the most animal foods.

The health outcomes measured in this study were heart disease events, heart disease deaths, and all-cause deaths. Again, for the sake of simplicity, I will only include 2 of these outcomes (heart disease deaths and all-cause deaths) in this review. The data on deaths were obtained from state death records and the National Death Index. (Yes, your personal information is available on the web even after you die.)

 

Do Plant-Based Diets Reduce Heart Disease Deaths?

plant-based diets reduce heart deathsThe participants in this study were followed for an average of 25 years.

The investigators looked at heart disease deaths over the 25 years and compared people with the highest intake of plant foods to people with the highest intake of red meat and other animal foods. The results were:

  • People with the highest intake of plant foods and the highest intake of healthy plant foods (whole grains, fruits, vegetables, nuts, legumes, coffee and tea) had a 19-32% lower risk of dying from heart disease than people with the highest intake of red meat and other animal foods.
  • People with the highest intake of unhealthy plant foods (refined grains, fruit juices, French fries and chips, sugar sweetened and artificially sweetened beverages, sweets and desserts) had the same risk of dying from heart disease as people with the highest intake of red meat and other animal foods.

When the investigators looked at all-cause deaths over the 25 years:

  • People with the highest intake of plant foods and the highest intake of healthy plant foods had an 11-25% lower risk of dying from any cause than people with the highest intake of red meat and other animal foods.
  • People with the highest intake of unhealthy plant foods had the same risk of dying from heart disease as people with the highest intake of red meat and other animal foods.

What Else Did The Study Show?

The investigators made a couple of other interesting observations:

  • The association of the overall diet with heart disease and all-cause deaths was stronger than the association of individual food components. This underscores the importance of looking at the effect of the whole diet on health outcomes rather than the “magic” foods you hear about on Dr. Strangelove’s Health Blog.
  • Diets with the highest amount of healthy plant foods were associated with higher intake of carbohydrates, plant protein, fiber, and micronutrients, including potassium, magnesium, iron, vitamin A, vitamin C, folate, and lower intake of saturated fat and cholesterol.
  • Diets with the highest amount of unhealthy plant foods were associated with higher intake of calories and carbohydrates and lower intake of fiber and micronutrients.

The last two observations may help explain some of the health benefits of plant-based diets.

 

Can Plant-Based Diets Be Unhealthy?

plant-based diets unhealthy cookiesNow, let’s return to the question I asked at the beginning of this article: “Can plant-based diets be unhealthy?” Although some previous studies have suggested that unhealthy plant-based diets might increase the risk of heart disease, this study did not show that.

What this study did show was that an unhealthy plant-based diet was no better for you than a diet containing lots of red meat and other animal foods.

If this were the only conclusion from this study, it might be considered a neutral result. However, this result clearly contrasts with the data from this study and many others showing that both plant-based diets in general and healthy plant-based diets reduce the risk of heart disease deaths and all-cause deaths compared to animal-based diets.

The main message from this study is clear.

  • Replacing red meat and other animal foods with plant foods can be a healthier choice, but only if they are whole, minimally processed plant foods like whole grains, fruits, vegetables, nuts, legumes, coffee and tea.
  • If the plant foods are refined grains, fruit juices, French fries and chips, sugar sweetened and artificially sweetened beverages, sweets and desserts, all bets are off. You may be just as unhealthy as if you kept eating a diet high in red meat and other animal foods.

There is one other subtle message from this study. This study did not compare vegans with the general public. Everyone in the study was the general public. Nobody in the study was consuming a 100% plant-based diet.

For example:

  • The group with the highest intake of plant foods consumed 9 servings per day of plant foods and 3.6 servings per day of animal foods.
  • The group with the lowest intake of plant foods consumed 5.4 servings per day of plant foods and 5.6 servings per day of animal foods.

In other words, you don’t need to be a vegan purist to experience health benefits from adding more whole, minimally processed plant foods to your diet.

 

The Bottom Line

A recent study analyzed the effect of consuming plant foods on heart disease deaths and all-cause deaths over a 25-year period.

When the investigators looked at heart disease deaths over the 25 years:

  • People with the highest intake of plant foods and the highest intake of healthy plant foods had a 19-32% lower risk of dying from heart disease than people with the highest intake of red meat and other animal foods.
  • People with the highest intake of unhealthy plant foods had the same risk of dying from heart disease as people with the highest intake of red meat and other animal foods.

When the investigators looked at all-cause deaths over the 25 years:

  • People with the highest intake of plant foods and the highest intake of healthy plant foods had an 11-25% lower risk of dying from any cause than people with the highest intake of red meat and other animal foods.
  • People with the highest intake of unhealthy plant foods had the same risk of dying from heart disease as people with the highest intake of red meat and other animal foods.

The main message from this study is clear.

  • Replacing red meat and other animal foods with plant foods can be a healthier choice, but only if they are whole, minimally processed plant foods like whole grains, fruits, vegetables, nuts, legumes, coffee and tea.
  • If the plant foods are refined grains, fruit juices, French fries and chips, sugar sweetened and artificially sweetened beverages, sweets and desserts, all bets are off. You may be just as unhealthy as if you kept eating a diet high in red meat and other animal foods.

A more subtle message from the study is that you don’t need to be a vegan purist to experience health benefits from adding more whole, minimally processed plant foods to your diet. The people in this study were not following some special diet. The only difference was that some of the people in this study ate more plant foods and others more animal foods.

For more details on the study, read the article above.

 

These statements have not been evaluated by the Food and Drug Administration. This information is not intended to diagnose, treat, cure or prevent any disease.

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