Not Written in Stone

"It runs in the family." Most of us have said it, about heart disease, diabetes, weight, low mood or memory loss, as though our future was written in our DNA at birth. For much of the twentieth century, science agreed. But one of the most remarkable discoveries of recent decades has turned that idea on its head. Your genes are not a fixed set of orders. They are more like a piano keyboard, and the way you live decides which keys are played, how loudly, and which stay silent.

The switches on your genes

Almost every cell in your body contains the same DNA, yet a skin cell, a liver cell and a brain cell behave completely differently. The difference lies in which genes are switched on and which are switched off. This layer of control is called the epigenome, from the Greek epi, meaning "on top of".

One of the best-known switches is DNA methylation: tiny chemical tags, made partly from nutrients in our food, that attach to genes and usually quieten them. Others work by loosening or tightening the way DNA is wrapped around its protein spools, making genes easier or harder to read. Crucially, these switches respond to the world around us: to what we eat, how we move, how we sleep, the stress we carry and the chemicals we meet.

Even identical twins, who share exactly the same DNA, grow more different epigenetically as the years go by, especially when they live apart and lead different lives.¹ It's one reason why one twin may develop a disease while the other stays well.

Nature offers a beautiful example. Every honeybee larva in a hive starts life with the same DNA, yet the few fed generously on royal jelly grow into queens: larger, fertile, and living for years, while their sisters become workers who, in summer, live for only a few weeks. In 2008, Australian researchers showed that this works through the epigenome. When they quietened the gene for an enzyme that adds methyl tags (DNMT3) in newly hatched larvae, most of them developed into queens with fully formed ovaries, just as though they had been fed royal jelly.² Same genes, different food, a completely different life.

The mice that changed colour

In 2003, researchers at Duke University carried out an experiment that still astonishes. They worked with a strain of mice carrying a gene called agouti, which, when switched on, makes them yellow, obese and prone to diabetes and cancer. Before and during pregnancy, some mothers were fed a diet rich in methyl donors, nutrients such as folate, vitamin B12, choline and betaine, found in leafy greens, beans, eggs and beetroot. (See Fertile Ground.)

Their babies were born genetically identical to the others, yet many were slim, brown and healthy. The mothers' diet had added methyl tags that quietened the troublesome gene, and the effect lasted throughout the babies' lives.³ In a later study, exposing pregnant mice to bisphenol A (BPA), a chemical found in some plastics, pushed more babies towards the yellow, unhealthy type, but a diet rich in methyl donors largely protected them.⁴ (See Lightening the Load.)

Genes load the gun, but environment pulls the trigger.

Echoes through the generations

In the winter of 1944, a German blockade cut off food to the western Netherlands. During the "Hunger Winter", people survived on as little as 400 to 800 calories a day. Children who were in the womb during the famine were followed for decades, and the findings were striking: those exposed in early pregnancy had higher rates of heart disease, obesity and raised cholesterol as adults.⁵ Sixty years later, their DNA still carried a different pattern of methylation on a gene involved in growth and metabolism, compared with their brothers and sisters born before or after the famine.⁶

Even more remarkable are the records of Överkalix, a remote village in northern Sweden, where harvests were carefully recorded for centuries. Researchers found that the food supply available to grandparents during their own childhood, in the years just before puberty, was linked with their grandchildren's risk of dying from heart disease and diabetes.^7,8 The effects followed the sex of the grandparent: grandfathers' food supply was linked with grandsons, and grandmothers' with granddaughters.

Studying effects across generations in people is enormously complex, as families share homes, habits and circumstances, as well as genes, and scientists are still unravelling exactly how such effects are passed on. But the consistency of these findings, alongside careful animal research, suggests that our lives leave marks that can reach the generations that follow.

Fathers matter too

Pre-conception health has long been seen as a mother's responsibility, but sperm carry epigenetic marks as well. In one study, men's sperm showed significant changes in methylation, including on genes linked with appetite, within a year of major weight loss.⁹ This suggests that a father's diet, weight and lifestyle before conception may matter more than we ever imagined, and that both parents can give their future children a healthier start.

How care shapes the stress response

Some of the most moving research concerns the way we are cared for. Rat pups whose mothers licked and groomed them more grew into calmer adults, and the difference was traced to epigenetic marks on the gene for the stress-hormone receptor in the brain. When pups were swapped between mothers at birth, it was the care they received, not the mother they were born to, that set the switch.¹⁰ In people, similar marks have been found in the brains of adults who suffered abuse in childhood.¹¹

The hopeful part is that these marks are not necessarily permanent. In the rat studies, the effects could be reversed later in life, and in people, the brain and body remain able to change throughout life. (See The Cortisol Clock and Social Resonance.)

The good news: change can start in weeks

If the switches respond to the way we live, then they respond to positive change too, and sometimes surprisingly quickly:

• Food. In a small trial, eight weeks of a diet rich in vegetables, leafy greens, beetroot, seeds, eggs and liver, together with exercise, sleep and relaxation, reduced participants' "epigenetic age" by an average of about three years compared with the control group.¹² Many everyday foods contain compounds that influence epigenetic switches, including sulforaphane in broccoli, the catechins in green tea, curcumin in turmeric, and the folate in greens and beans. (See Food as Medicine.)
• Movement. Even a single session of exercise changes methylation in muscle genes involved in using energy,¹³ and six months of regular exercise changed the methylation of hundreds of genes in fat tissue.¹⁴ (See Born to Move.)
• Calm. After just one day of mindfulness practice, experienced meditators showed lower activity in genes that drive inflammation, along with changes in the enzymes that control epigenetic switches.¹⁵ (See The Sound of Stillness.)
• Lifestyle as a whole. In men with early prostate cancer, three months of whole-food eating, exercise, stress management and group support changed the activity of around 500 genes, quietening many linked with tumour growth.¹⁶

Tending your genes

• Eat the rainbow, with plenty of leafy greens, beans, lentils, beetroot, brassicas, eggs, nuts and seeds for the nutrients that make methyl tags.
• Drink green tea and use turmeric, herbs and spices generously.
• Move every day, mixing walking with strength.
• Protect your sleep and calm your nervous system. (See The Art of Sleep.)
• Lighten your chemical load, especially before conception and in pregnancy. (See Why Eat Organic?)
• Nurture connection and care, for yourself and for the children in your life.

At Rootwise, we never see a family history as a life sentence. We look at the whole person, and the everyday choices of food, movement, rest and calm that help your genes, and perhaps your children's genes too, express themselves at their very best.