by guest blogger Pam Peeke, MD, MPH, FACP, best-selling author and expert on health, fitness, and nutrition
At some point, you’ve learned that “you are what you eat.” Consume junk food and your risk for heart disease, diabetes, and cancer skyrockets. Grab an apple instead of a Twinkie, and your body rewards you with a strengthened immune system, as life-giving phytonutrients flood your tissues and organs. You feel empowered by your lifestyle choices. You are what you eat.
But this belief was challenged and expanded upon when, in 2008, Duke University’s Randy Jirtle, PhD, published a groundbreaking study proving that you’re not only what you eat, but also what your parents ate. In his experiment, he used the agouti mouse, named for the agouti gene in its genome, which causes the mouse to be obese and die prematurely of heart disease and diabetes. Because of a cross-linkage with the gene that controls fur color, the agouti mouse was yellow. Typically, the agouti offspring were identical to their parents and suffered the same life-shortened fate. Jirtle and his team decided to see if there was any way to partially or completely deactivate this gene. They chose one simple intervention: changing the mother’s diet before conception to a diet rich in methyl donors—CH3 side chains scientists believed could switch off the agouti gene. Methyl donors are commonly found in many foods, including leafy greens, beets, onion, and garlic. Lo and behold, the mice born to the methyl-donor–nutrified mothers were brown and lean and demonstrated no increased disease vulnerability. The agouti gene had been quieted.
Jirtle’s work led to the birth of epigenetics, possibly the most exciting new scientific development of the 21st century. We have all heard about the famous Genome Project, in which geneticists catalogued the existence of 25,000 genes. With the foundation of the Epigenome Project, scientists can now study how to switch genes on and off through a variety of interventions. New research has revealed that in addition to nutrition, interventions like exercise and meditation also profoundly affect how a gene messages to the rest of the body. In essence, you cannot change your genes, but you can most definitely alter how that gene commands changes throughout the body.
Researchers then asked the question, “If parents’ diet and lifestyle could induce significant changes in their children, what about the grandparents’?” Thanks to the terrific work done by scientists in Britain and Sweden, we’ve discovered that what grandparents ate and what they did in life significantly affected gene expression in their grandchildren. Marcus Pembrey, MD, a geneticist from the Institute of Child Health in London, collaborated with Swedish researcher Lars Olov Bygren, MD, PhD, and found a solid basis of evidence depicting transgenerational epigenetic inheritance.
Using the Avon Longitudinal Study, the two reviewed data derived from British children born to 14,000 mothers in the early 1990s. Specifically, they found that in the study more than 5,000 fathers were either active or prior smokers. Of those smokers, 166 had begun smoking during the slow-growth phase that occurs from age 9 to age 12. It’s during this time that genes are very vulnerable to epigenetic influences, from nutrition to smoking.
The researchers found that:
- The sons of men who had smoked in preadolescence (between 9 and 12 years old) were significantly more overweight by the time they had reached 9 years of age.
- A review of the data from the feast or famine records of a small remote Swedish town, Overkalix, showed that if famine took place during the preadolescent years of the grandfather, fewer sons died early.
- If the grandfather experienced overeating during the preadolescent years, the number of sons dying from all causes increased, shortening the life span by six years.
- Granddaughters were not affected by these nutritional changes.
Dutch scientists added even more grist to the epigenetic mill by analyzing the meticulous records kept during and after the horrific 1944 Dutch Hongerwinter, which took place when towns in the western part of Holland were blockaded during World War II. The blockade resulted in 22,000 people dying from malnutrition, as the average daily caloric intake was reduced to 580 calories. What were the effects of prenatal famine on offspring? The infants who did survive were more susceptible to health problems, but their own children, born years later, were significantly underweight. The famine, therefore, had a profound effect on gene expression two generations later.
This has turned the traditional belief that life is about nature versus nurture on its head. What this really means is that nature (our genes) is intimately intertwined with nurture (our environment), and these epigenetic changes have deep roots in the choices of our grandparents, and in those of their grandparents.
The emergence of epigenetics has provided us with two gifts. One is a forewarning that the way we live today does have significant consequences for our children, our grandchildren, and beyond. And the second gift is one of empowerment. Regardless of what took place two generations before us, we still have tremendous power to modify our own gene expression with every thought, every mouthful, and every physical movement we choose to engage in. Our genes are waiting for direction from us. My advice? Go for the apple.
Pamela Peeke, MD, MPH, FACP, is a Pew Scholar in nutrition and metabolism, assistant professor of medicine at the University of Maryland, and a fellow of the American College of Physicians. A triathlete and mountaineer, she is known as “the doc who walks the talk,” living what she’s learned as an expert in health, fitness, and nutrition. Dr. Peeke is featured as one of America’s leading women physicians in the National Institutes of Health Changing Face of Medicine exhibit at the National Library of Medicine. Her current research at the University of Maryland centers on the connection between meditation and overeating. She is the author of many best-selling books, including Fight Fat after Forty. Her new book is the New York Times best-seller The Hunger Fix.