Could a woman’s diet or weight while she’s pregnant impact whether her child has a higher risk of illness years later? Why don’t identical twins always have the same personality or same risk of disease, even though they have the same set of genes? The answers may lie in how our cells turn our genes on and off like a light switch.
We know that heredity does play a role in a large number of diseases such as diabetes, Alzheimers and cancer, but to what extent we do not know. Mutations in genes only account for a minuscule portion of the inherited risks, explains geneticist Evan Rosen of Harvard’s Beth Israel Deconess Medical Center in Boston. “We’re finding that the impact of genetics on health is much more complicated than just the DNA sequence in an individual’s genes,” further explains Rob Waterland, an associate professor of pediatrics and molecular and human genetics at the Baylor College of Medicine in Houston.
Genes are essentially strings of DNA that serve as blueprints for synthesizing all sorts of proteins that make life possible, such as insulin, heart muscle, antibodies, among other things. Some of our 20,000 genes are always active, producing their proteins, while others get switched on and off at different times. What flips the switch? Epigenetic marks.
Lets get a little technical… A common example is a methyl group – which consists of a carbon atom bonded with three hydrogen atoms. When enough methyl groups become attached to a gene, they can turn the gene off. The same can happen when methyl groups become attached to the histone proteins that DNA strands wrap themselves around. But if enough acetyl groups – each consist of two carbons, one oxygen, and three hydrogen atoms – become attached to a histone, the gene may get switched on.
Some of these epigenetic marks appear soon after conception and last an entire lifetime, such as ones that tell the genes in brain cells to make more brain cells but not liver cells. Others can appear and disappear at any time, in response to diet, weight, stress, and exposure to tobacco or chemicals like DDT. Whats exciting about this is the concept of altering epigenetic marks with our diets.
So far researchers know that certain compounds in foods can change epigenetic marks in cancer cells, at least in test tubes. For example, the curcumin in tumeric, the EGCG in green tea, the genistein in soybeans, the resveratrol in grapes, and the sulforaphane in cruciferous vegetables like broccoli can hinder the enzymes that help attach methyl groups or remove the acetyl groups from genes. However, there is still a lot to be figured out such as whether people can absorb enough of these substances from food, whether the compounds they’re metabolized into can get to the right cells, and how rapidly we can clear, or remove, the compounds from our bodies.
What I find extremely interesting is the relationship between epigenetics and pregnancy.
For instance, Rob Waterland, among other researchers have found that the nutritional status of a mother during pregnancy can have a profound, lifelong impact on whether her children become overweight or obese. In studies looking at babies conceived during times of war, when food was scarce, those children were much more likely to be overweight or obese later in life. Researchers found that an important gene for growth during pregnancy (the blueprint for making insulin-like growth factor-2, or IGF2) was less methylated – more turned on – in people who had been conceived during the worst of the starvation period than in those who were less than six months away from being born.
Also very interesting are two more studies that examined 162 obese Canadian mothers who had children before, and then after, weight-loss surgery. The children who were born after the surgery were half as likely to grow up overweight or obese as the children who were born before the surgery. It was also discovered that the children born after the surgery were found to have different epigenetic marks than those born before the surgery. But its important to note that there could be other factors. For example, weight-loss surgery could have changed the women’s gut microflora or blood sugar levels, or how efficient their bodies were at using insulin to get glucose into the cells. These factors could have accounted, at least partly, for changes in their children’s weight.
But, its not just mothers who matter. In another study looking at 79 newborns, Duke University researchers reported that the gene for IGF2 was less methylated – more turned on – in those born to obese fathers than in those born to normal-weight fathers. This may very well increase those children’s risk of becoming obese adults.
How much newborns eat soon after birth is also critical. Just as the effects of newborns not receiving adequate nutrition can be deeply problematic, consuming too much can be equally detrimental. In a 2013 study, Rob Waterland and colleagues found that mice that were overfed during their first few weeks of life showed subtle changes in the methylation of genes in their hypothalamus that persisted into adulthood. (The hypothalamus is a specialized region of the brain that helps regulated body weight). These overfed mice grew up to become heavier and fatter adults. “Epigenetic changes can be induced by over-nutrition and may have a major long-term impact on behavior and weight,” says Waterland.
Genes aren’t everything. What we put in our bodies and what we expose ourselves to impacts us in much greater ways than we may have realized. Not only do food and drugs, toxins and chemicals affect our own epigenetics, but also those of our children and our great grand children.
–Epigenetics may help explain how diet, body weight, physical activity, stress, or exposure to chemicals may increase or decrease our risk of heart disease, cancer, diabetes, and other illnesses.
–We can’t change our genes, but we may be able to change our genes’ epigenetic marks with food or drugs.
–Not all epigenetic changes are beneficial.
–Use this information as a tool to be make better choices and be more aware of the impact we have on our bodies and those of our offspring!
Sources:Nutrition Action Newsletter July/August 2013