What is epigenetics: how gene activity is regulated and what is supported by evidence

What to expect in this article

1. What epigenetics is and what it is not
2. Genome and epigenome: the difference in one image
3. The three mechanisms that regulate gene activity
4. How epigenetic marks arise and how stable they are
5. Four statements about epigenetics that go too far
6. The winter famine of 1944/45 and what the cohorts really show
7. Sequence, methylation, gene expression: what to distinguish from what
8. Epigenetic age tests are a research field of their own
9. What a commercially available saliva test actually reads
10. What the longevity test covers and what it does not
11. Who should even consider having a genetic analysis
12. Limits: where epigenetics ends today
13. What ultimately matters
14. Frequently asked questions
15. Sources

What epigenetics is and what it is not

Epigenetics is a field of research, not a procedure or a product. It examines changes in gene activity that occur without a change to the DNA sequence. The word itself indicates where it operates: the Greek prefix epi means “above,” and that is precisely where the regulatory level lies—above the text, not within it.

The U.S. National Library of Medicine describes epigenetic changes in its genetics portal as modifications to DNA that do not alter the sequence of its building blocks (as of 2021). This wording is the dividing line for the entire field. What changes the sequence is a mutation. What changes readability is an epigenetic mark.

Why a liver cell is not a nerve cell

Every nucleated body cell in a human carries the same DNA. A liver cell and a nerve cell therefore differ not in their blueprint, but in which parts of it are read. This very question was the starting point of epigenetics, long before it became associated with diet or lifestyle.

The development of an embryo is therefore the textbook example of the field. Hundreds of cell types arise from a single fertilized egg without the blueprint changing. What differs is how it is read. A field that answers this question is initially developmental biology, not lifestyle management.

This origin explains much of what goes wrong today. A mechanism that keeps cell identity stable is turned in advice articles into a switch that one flips at the breakfast table. Research describes both: highly stable markers and highly dynamic ones. Which of the two is meant determines the significance of every statement.

Genome and epigenome: the difference in one picture

A picture is more helpful here than a second definition. Every cell in your body carries the same staff. What distinguishes the cells from one another is the work schedule: who is working today, who has the day off, and who is not called in at all.

The genome is the staff list. It is identical in every cell and changes practically not at all over the course of a lifetime. The epigenome is the work schedule. It differs from one cell type to another, is continuously updated, and determines which capabilities of the staff are actually put to use on a given day.

This picture reveals the most important practical difference. Anyone who reads a staff list gets a result that remains valid for a lifetime. Anyone who reads a work schedule gets a snapshot from a specific tissue at a specific point in time. Both are measurements, but they answer different questions and age at entirely different rates.

The picture has a limit, and that limit matters. A work schedule is written by someone who can choose it freely. An epigenome arises simultaneously from developmental programs, cell division, age, tissue, and the environment. No one sits down and enters a line.

The three mechanisms that regulate gene activity

In the scientific literature, three mechanisms are regarded as the main pillars of epigenetic regulation: DNA methylation, histone modification, and regulation through non-coding RNA. They do not work independently of one another, but they act at different points.

DNA methylation: a mark directly on the letter

In DNA methylation, a methyl group—that is, a very small chemical attachment—is bonded to one of the building blocks of DNA. The U.S. National Library of Medicine describes the consequence as the affected gene being silenced, so that no protein is produced from it (as of 2021). The letter remains in place; it is simply no longer read.

Methylation is the best-studied of the three mechanisms, and there is a technical reason for that. It occurs at defined positions, persists through cell division, and can be measured at thousands of sites simultaneously in the laboratory. That is why almost everything you read about epigenetics in numerical terms is actually a statement about methylation.

Histone modification: how tightly the strand is coiled

DNA does not lie loose in the cell nucleus. It is wrapped around proteins called histones, which act like spools. The U.S. National Library of Medicine describes how chemical groups can be added to or removed from these histones, changing how tightly the DNA is coiled (as of 2021).

Tightly coiled means inaccessible; loosely coiled means readable. This mechanism therefore regulates not individual letters but entire sections at once. It is more dynamic than methylation and therefore harder to measure as a stable finding.

Non-coding RNA: regulation after transcription

The third level comes into play later. Non-coding RNAs are RNA molecules from which no protein is made and which instead perform regulatory tasks. They can block the translation of a transcribed gene copy or accelerate its breakdown.

In practice, this third pillar is the least conspicuous because it does not appear in any consumer test. It is important for understanding because it shows how many steps lie between a gene and an effect. A gene is not a statement about a person, but the beginning of a long chain.

How epigenetic marks arise and how stable they are

Several stages lie between an external stimulus and altered gene activity. The following overview presents them in the order in which they are described in the scientific literature. It is an organizational aid, not an instruction manual.

The final stage is where most texts stop. But it is the crucial one. A changed readout at a handful of gene sites is a measurable finding, not a health event. The entire rest of biology lies between the two.

There are two answers regarding stability, and they only appear to contradict each other. The markers that make a liver cell a liver cell remain stable for decades and survive every cell division. Other markers change within hours. Anyone who talks about epigenetics without saying which kind they mean is saying almost nothing.

Are epigenetic markers inherited?

This question is the most popular part of the field and also the part where people most quickly say too much. The U.S. National Library of Medicine states that epigenetic modifications can be passed from cell to cell during cell division and, in some cases, across generations (as of 2021). The phrase “in some cases” carries all the weight.

Two things are regularly conflated here. The first is transmission within a body: A skin cell divides, and the daughter cell remains a skin cell. This transmission is undisputed and forms the basis of every tissue identity.

The other is transmission through the germ cells to the next generation. During the formation of egg and sperm cells, and again during early embryonic development, large parts of the markers are cleared and reset. This very twofold reset is why the transmission of acquired patterns to children and grandchildren in humans remains an active area of research and is not an established everyday claim.

Four statements about epigenetics that go too far

Few areas of biology have been exaggerated so often. The appeal lies in the message: Anyone who says that genes are destiny has nothing to sell. Anyone who says they can be rewritten suddenly has a great deal to sell. The following three comparisons dissect the most common claims.

Widespread versus substantiated

The fourth sentence is the quietest and the most consequential. It says that a genetic test shows which genes are currently switched on or off in your body. No commercially available genetic test does that, because it reads the sequence, not the markers on it. Chapter 9 examines this point in detail.

None of these sentences is made up. Each starts from a genuine finding and loses, on its way into advertising, precisely the detail that made it sound: the model system, the scale, the condition. Putting the condition back beside it does not diminish epigenetics. It simply puts it in the right place.

The famine winter of 1944–45 and what the cohorts really show

In the winter of 1944–45, food supplies in parts of the occupied Netherlands were severely restricted for months. Because the birth cohorts and the duration of the famine are well documented, these cohorts are among the most frequently studied groups in epigenetics. They are the human counterpart to the agouti mice.

A study by Tobi and colleagues compared 60 people who were affected by the famine around the time of conception with one unaffected same-sex sibling each. Five regulatory regions in the IGF2/H19 region were examined, an area whose expression is known to be epigenetically regulated (PLoS ONE, 2012).

The result is informative in both directions. Consistent differences in methylation were found, specifically in all the IGF2 regions examined. At the same time, these differences were small, below three percent. The sibling comparison makes the finding robust because it largely accounts for the influence of the family.

That is precisely where the value of these cohorts lies for an honest text. They demonstrate that an environmental condition can leave a lasting mark on the epigenome six decades after the event. And they show how large that mark is after one of the most extreme exposures that can be documented in humans at all.

Anyone who concludes from this study that a two-week diet plan remodels the epigenome has skipped several orders of magnitude. The benchmark was a months-long famine during the most sensitive phase of development. A breakfast is not a winter of hunger.

Sequence, methylation, gene expression: what needs to be distinguished from what

Three things are constantly confused in everyday life, even though they involve different laboratories, different samples, and different claims. The table places them side by side according to the same criteria.

The last line is why this article does not end with a testing offer that fulfills its own headline. A saliva test reads the sequence. It does not capture the epigenetics discussed here on every page.

This also puts the related topics in order. What a genetic predisposition says about nutrient metabolism is covered in our article Genetic nutrition test: what it shows and what it costs. The article Nutrigenetics test reviews assesses how reliable it is to derive dietary recommendations from such predispositions. This article stays with the question that comes before that: what epigenetics actually is.

Epigenetic age tests are a distinct field of research

Anyone exploring epigenetics quickly encounters biological age. The idea behind it is elegant: if methylation patterns systematically shift with age, an age can be calculated from them. That is precisely what so-called epigenetic clocks do.

The best-known one was developed by Steve Horvath and published in Genome Biology in 2013. It is based on 353 methylation sites, was developed using around 8,000 samples from 51 healthy tissues and cell types, and estimated chronological age in the test data with a median deviation of 3.6 years. The author describes the result as a measure of the cumulative effect of an epigenetic maintenance system.

What a clock measures and what it does not measure

A clock trained on chronological age is initially an estimation tool for chronological age. The idea that a downward deviation means a better condition and an upward deviation a worse one is an additional assumption that requires its own evidence. It does not follow from the clock itself.

There is also the tissue issue from the table above. Methylation patterns differ between blood, skin, and liver. A clock calibrated for one tissue initially says nothing about another. That is precisely why stating which sample a value comes from is not a detail but half the meaning.

One point is important for understanding this article, and it is deliberately stated here in the middle rather than at the end. Epigenetic age tests are not part of the mybody®x (MYBODY Lab GmbH) product range. They are described here because they belong to the field, not because any product covers them.

What a retail saliva test actually reads

DNA tests for consumers predominantly use SNP genotyping. An SNP, pronounced like the English word snip, is a position in the genome where people regularly differ in a single building block. Such a test does not read the entire genome; instead, it examines a predefined selection of these positions.

This is a sequence analysis. It answers the question of which variant someone carries at a particular location. It does not answer whether that location is currently methylated, how tightly it is packaged, or how much of it is transcribed. A test that reads the sequence does not measure methylation.

This leads to a practical characteristic that is often interpreted as a disadvantage but is actually not one. Because the sequence does not change, the result does not change. A genotyping result from today remains unchanged twenty years from now. A methylation result from today would be different in a year if it were measured again.

Conversely, this also means that a saliva test cannot show what your lifestyle has changed in your gene activity. Anyone asking this question is asking an epigenetic question, and this method does not answer it. This is not a weakness of any individual provider, but a characteristic of the method.

Why the sample type is half the answer

For genotyping, saliva is a sensible sample because the sequence is the same in every cell with a nucleus. It does not matter whether the cells come from the oral mucosa or the blood. The blueprint is present everywhere in the same version.

For a methylation analysis, the opposite is true. There, the sample determines what the result means because the markings differ between tissues. That is why epigenetic tests use a defined sample, usually blood, and why a methylation result is always a result concerning that one tissue.

Almost everything in this article follows from this one technical distinction. The sequence is the same everywhere and permanent; the marking is tissue-specific and changeable. Once you understand this, you can recognize within a minute which of the two questions any test offering can actually answer.

What the Longevity test covers and what it does not

At this point, a product of its own belongs in the text, and it should be included with the same precision as everything that came before. The Longevity ALL IN ONE DNA Test from mybody®x is a saliva test based on genotyping. According to the product page, more than 170 genetic variations are analyzed, from which reports on nutrition, exercise, metabolism, and skincare are derived, accessed on 08/27/2026.

What this test does not do is more important for this article than what it does. It does not measure DNA methylation. It does not determine methylation age or an epigenetic clock. It does not show which of your genes are currently active. It is an assessment of predisposition, not of current state.

One point requires explicit clarification, because it could otherwise be misunderstood. The product page lists a report on biological aging that analyzes a component of telomerase. This is a gene locus in the sequence and therefore a predisposition, not a measurement of epigenetic age. Equating the two confuses two different methods.

DNA test from a saliva sample

Longevity | ALL IN ONE DNA Test

According to the product page, analyzes more than 170 genetic variants and derives suggestions for nutrition, exercise, metabolism, and skincare. What the test does not do: It does not measure DNA methylation, determine epigenetic age, show which genes are currently being read, provide a diagnosis, or predict future developments. It describes predispositions, not a current state.

Price €369.00 As of 27 August 2026; subject to change

Sample type Saliva sample

Processing time Kit shipping 1–3 business days
Laboratory analysis 15–25 business days after sample receipt

Laboratory laboratory-guided analysis
Information from the product page, accessed 27 August 2026

About the Longevity ALL IN ONE DNA Test

The bridge from this article to this product is therefore short, and it should remain short. Anyone searching for epigenetics is looking for an explanation. A genotyping test is not the answer to that, but rather provides related information: it describes the predisposition on which epigenetic regulation operates. If you want to know about that predisposition, it is the right choice for you. If you want to have your epigenome measured, it is not.

Who might consider genetic analysis at all

After everything discussed in this article, one practical question remains. It is not whether epigenetics is interesting, but whether a commercially available test answers something for you. The following comparison sets out both sides.

The right-hand column is the more honest part of this page. It contains no watered-down benefits, but three cases in which the answer is simply no. Anyone in one of them saves 369 euros and still learns something.

Boundaries: where epigenetics ends today

The first boundary is the distinction between association and cause. Many epigenetic findings are observations of groups: people with characteristic A show a different methylation pattern at site B. Whether the marking causes the characteristic, the characteristic causes the marking, or a third factor produces both remains unclear.

The second boundary is magnitude. The differences found in well-controlled human studies are usually small. That does not invalidate them, because even small shifts at regulatory sites can mean something. But it rules out the language of switching, which suggests a toggle.

The third boundary is tissue. What is measured in a blood sample applies to blood cells. It cannot readily be inferred from that for the liver, adipose tissue, or brain. In a field whose entire point is cell-type specificity, this is not a minor detail.

The fourth boundary is legal, and it is non-negotiable. Neither a genotyping test nor a methylation analysis is a method that detects, treats, or prevents a disease. When symptoms are present, the route is through medical evaluation, not a self-test.

What matters in the end

It began with the observation that epigenetics does not change the text, but the bookmarks. That is precisely where the field's importance lies—and at the same time its susceptibility to exaggeration. A bookmark is easier to imagine than a mutation, and is therefore easier to promise.

What remains from this article are three verifiable statements. Epigenetics describes regulation without changing the sequence. Environmental conditions leave traces in it, whose magnitude is small in human studies. And a commercially available DNA test measures none of this because it uses a different method.

This leads to a question you can now apply to any text selling you epigenetics: Which sample, which tissue, what magnitude? A text that answers none of these three has no finding, but an image. You can recognize that now in ten seconds.

Frequently asked questions

Sources

1. U.S. National Library of Medicine, MedlinePlus Genetics: What is epigenetics? (as of 2021) – medlineplus.gov
2. Max Planck Society: Epigenetics – Changes beyond the genetic code (2016) – mpg.de
3. Tobi EW, Slagboom PE, van Dongen J and colleagues: Prenatal Famine and Genetic Variation Are Independently and Additively Associated with DNA Methylation at Regulatory Loci within IGF2/H19. PLoS ONE, 2012 – journals.plos.org
4. Horvath S: DNA methylation age of human tissues and cell types. Genome Biology, 2013 – genomebiology.biomedcentral.com

The description of DNA methylation and histone modification, as well as the distinction from the DNA sequence, is based on [1]. The direct quotation on the regulation of gene activity comes from [2]. The figures on the Hunger Winter—namely, the 60 sibling pairs compared and the differences of less than three percent in the IGF2 regions—come from [3]. The information on the epigenetic clock, with 353 methylation sites, around 8,000 samples, 51 tissues, and a median deviation of 3.6 years, comes from [4]. The finding concerning Agouti mice comes from a study by Waterland and Jirtle in Molecular and Cellular Biology (2003); it is attributed in the main text with the authors, journal, and year and is therefore not included in this list. Information on price, gene variations, sample type, and laboratory comes from mybody®x's product page, accessed on 27.08.2026; processing times follow the central specifications for DNA tests. All sources were accessed and checked on 27.08.2026.

mybody®x Editorial & Expert Team

Nutrigenetics Laboratory diagnostics Nutritional science Molecular biology

This article was created by the mybody®x editorial and expert team. The team combines nutrigenetics, laboratory diagnostics, and nutritional science. Those who contribute to it are listed on the authors page.

Published on 25.08.2025 · Last updated on 27.08.2026

The DNA analysis is intended for nutritional and lifestyle counseling. It is not a diagnostic procedure, does not predict disease, and does not replace a medical examination or consultation. Genetic variants describe probabilities in population groups, not predetermined outcomes for individuals.