Imagine opening a book where every word is already printed. You cannot change them. But you can decide which pages get read and which stay closed — forever, or for now. That is exactly what epigenetics does with your DNA.
For a long time, genetics was seen as a lottery. You receive a combination of genes from your parents and everything is predetermined: height, temperament, susceptibility to disease. But over the last thirty years, scientists have uncovered something unexpected — between genes and how they actually work, there is an entire additional layer of control. That layer is called epigenetics, literally "above genetics".
The idea is straightforward. Every cell in your body carries the same set of roughly 20,000 genes. Yet a heart muscle cell behaves completely differently from a neuron or a pancreatic cell. What distinguishes them? Not the DNA itself, but which sections of it are being "read" and which are locked shut. Epigenetic marks are the bookmarks, sticky notes and padlocks inside your genetic book.
Genes are the question. Epigenetics is your body's answer to the conditions of your life.
The main tool of epigenetics is DNA methylation. Methyl groups (CH₃) attach to specific points on the molecule and silence the gene: it is still there, but it is not working. The reverse process, demethylation, switches a previously silent section back on. Histone modifications work the same way — the chemical state of the proteins around which DNA is wound determines how tightly chromatin is packed and whether a gene is accessible for transcription.
In 2003, American biologist Randy Jirtle published results of an experiment that turned our understanding of heredity upside down. The subject: mice carrying what is known as the agouti gene. When this gene is active, the mouse is born yellow, obese, and prone to diabetes and tumors. A genetic disaster in miniature.
Jirtle tried something simple: he switched pregnant mothers onto a diet rich in folic acid, vitamin B12, choline and betaine — all methyl-group donors. The result was stunning. The offspring were born lean, healthy and dark-furred, even though they carried the same "bad" gene. The methyl groups had effectively silenced it — without altering a single letter of the DNA sequence.
This experiment illustrated a principle that sounds revolutionary even today: what you eat during pregnancy can change the phenotype of your child — without touching their genetic code.
Winter, 1944–1945. Nazi Germany blockaded the western Netherlands, cutting off food supplies. Around 4.5 million people were pushed to the edge of starvation. Adults survived on 400–800 calories a day. Soup made from tulip bulbs became ordinary food.
When the war ended, Dutch epidemiologists made a remarkable discovery. People conceived during the blockade were significantly more likely, as adults, to suffer from obesity, type 2 diabetes, cardiovascular disease and even schizophrenia, compared to those conceived before or after the famine. Their bodies seemed to have "remembered" the scarcity and tuned themselves toward maximum storage.
More striking still: the children of those people — grandchildren of those who had starved — also showed elevated risk of metabolic disorders. The epigenetic marks formed under famine conditions had passed through a generation.
The Dutch Hunger Winter showed that the extreme experiences of our ancestors can leave a biological trace in our bodies — without changing a single letter of DNA.
Similar findings have emerged from studies of descendants of the Leningrad siege survivors, and from analyses of children of genocide survivors. Epigenetics is not a metaphor for inherited memory. It is the molecular mechanism behind it.
As early as 1942 — decades before molecular biologists had the tools to test his ideas — British scientist Conrad Waddington proposed his famous metaphor. Imagine a marble rolling down a hillside. Before it lies a landscape of valleys and ridges. Each valley represents one of the possible cellular fates. Ridges separate the paths.
The genome sets the shape of this landscape. But the landscape is not fixed — it is plastic. Diet, stress, physical activity, toxins, even sleep quality gradually reshape the hills and deepen the valleys. This is epigenetics in action: not a rewrite of the code, but a change in the route that life takes.
Epigenetics is not a reason for panic, nor a promise of omnipotence. But it shifts several important things in how we think about preparing for pregnancy.
A sperm cell takes around 74 days to mature. An egg completes its final stage of development in the 90–120 days before ovulation. That is precisely the window in which your lifestyle — nutrition, stress, toxins, activity — leaves epigenetic marks on your reproductive cells: that is, on the genetic material your child will receive.
Jirtle's experiment with agouti mice is not just a beautiful piece of science. It explains why folic acid — or more precisely its active form, methylfolate — reduces the risk of neural tube defects in the fetus: it supplies methyl groups at the exact moment the embryo's epigenome is forming most intensively. This is a direct epigenetic action.
Chronic stress raises cortisol levels, which through epigenetic mechanisms alters the activity of genes linked to inflammation, immune function and metabolism. In pregnant women with high anxiety levels, infants more often show heightened neural reactivity — and this is measurable in the epigenetic profile of cord blood.
For a long time, the epigenetics of pregnancy was seen as a story exclusively about mothers. Today we know otherwise. Research shows that a father's lifestyle during spermatogenesis — especially diet, alcohol, stress and age — influences the epigenetic profile of sperm and, through that, the health of offspring. In mice fed a folate-deficient diet, higher rates of developmental defects appeared in offspring regardless of the mother's nutrition.
If epigenetic marks can be placed, they can also be removed — or deliberately changed. That is exactly what several research teams around the world are working on, using tools analogous to CRISPR, but targeting not the DNA itself but its chemical "annotations".
In 2019, a group at the University of California reported successfully switching off a gene linked to alcohol dependence in rats using epigenetic editing. Rats that had previously consumed alcohol eagerly at every opportunity stopped seeking it — without behavioral training, without medication, purely through altering the methylation of a single gene in the brain.
This is not yet medicine for humans — too many questions remain about delivery, precision and long-term effects. But the direction is set, and research is moving fast.
Module 3 (Biohacking & Preconception) contains a concrete preparation protocol based on epigenetic research: which tests to run, which supplements have an evidence base and when they make sense. Available free in the Learn section.
the attachment of a methyl group (CH₃) to a cytosine base in DNA, typically silencing the gene at that location.
chemical changes to the proteins around which DNA is wound; they influence how tightly chromatin is packed and whether genes are accessible for transcription.
the transmission of epigenetic marks to offspring, bypassing the usual "reset" that occurs during the formation of reproductive cells.
the active, ready-to-use form of vitamin B9, requiring no enzymatic conversion.