What you do will remain in future DNA: diet and behavior across generations

Diet and behavior (smoking, drinking, physical activity, social interactions etc.) have a direct effect on your DNA! One cannot anymore say “It’s in my genes” and shake off responsibility for taking care of one’s own body, mind and health. We do have serious effects on our chances to diseases beyond what is written (and not necessarily transcribed) in our DNA sequence.

* Information number 1:

the responsibility of getting a disease is not JUST in the genes but up to us and our behaviour. Human biology is a very complicated business. “Everybody talks about the genes that they received from their mother and father, for this trait or the other. But in reality, those genes have very little impact on life outcomes…and genes are absolutely not our fate” (Craig Venter). What is written in your DNA (e.g. propensity towards certain diseases) does not necessarily mean that it is what will happen to you. It only gives a chance of things to happen. The chance becomes a reality when the environmental conditions (external or internal) “decide” which genes will work.

* Information number 2:

there is even more responsibility on ourselves since we pass on more inheritance to following generations than what we thought: it is not only what is written in the DNA sequence of our genes that we relay to our lineage but also what is carried in genes’ modification during our lifetime. Our behaviour, i.e. what we eat, if we smoke, drink or how we nurture our children will have cascade effects on the behaviour and HEALTH of our prole and their prole. Responsibility acts through behaviour across generations.

Both of these types of mechanisms are the result of epigenetics. Epigenetics is the science that studies cellular and physiological variations caused by external factors that switch genes on and off and affect how cells read genes. The genes are the blueprint of our physical and behavioural profile, but not all genes are always active in a cell. Actually, most of the about 20,000 genes in the human DNA are in an inactive phase or turned off (silenced) when not in use. In this phase, the string of DNA curls up around discs of proteins (histones) in a compact inaccessible form and cannot be ‘transcribed’, e. g. used to produce the proteins that are at the basis of our whole functioning system.

Figure from: http://learn.genetics.utah.edu/content/epigenetics/nutrition/

The epigenome is the compacted format of the DNA wrapped around the histones. It is a flexible structure that can be unwrapped when necessary to make parts of the DNA available. The wrapping is achieved by a simple chemical process, on pieces of DNA or on the histones, and this changes a cell's gene expression.

The simple chemical modifications or epigenetic changes (such as methylation, acetylation, phosphorylation etc.) that modify the 3D configurations of the DNA and free parts of it to be expressed are caused by environmental signaling such as diet and stress. Such epigenetic changes allow an organism to continually adjust its gene expression to fit its environment - without changing its DNA code.

This mechanism intervenes normally in the ‘differentiation’ of cells during development. All cells contain the same DNA sequence or list of genes, but only some genes are transcribed and used for producing certain proteins in each cell type. Skin cells will have only genes that produce skin proteins, while liver cells DNA will have only the genes that synthesize liver factors. This happens because the cells daughters of the first embryonic cell (union of father-sperm and mother-egg) modify into all the specialized different cell types (neurons, muscles cells, skin cells, etc.) by activating some genes while inhibiting the expression (silencing) of others.

Thus the genome or DNA of each cell contains two layers of information: the DNA sequence (code) inherited from our parents which is conserved throughout life and identical in all cells and among identical twins, and epigenetic marks (i.e., DNA wrapping/unwrapping and deactivation/activation) which are cell- , tissue- and individual-specific.

However, changes of the epigenome are not limited to the embryo development into a fetus but continue through life and regulate our existence from development to ageing as a result of exposure to a variety of environmental factors.

Environmental signals that are received by the epigenome come from inside the cell, from neighboring cells, or from the outside world (environment), i.e. before birth: food and stress hormones from the mother to the foetus, and after birth: social interactions, physical activity, diet and other inputs.

Some of the epigenetic changes can be dysregulated by physiologic mistakes, or are the response to negative signals from either the environment (toxins) or abnormal behaviour such as eating the wrong food or smoking or drinking alcohol when pregnant, wrong nurturing the child, bad food habits and bad behaviour when adult. All such cases can lead to harmful epigenetic changes that cause serious negative consequences like neuropsychiatric disorders and degenerative diseases. For example DNA epigenetic patterns resulting from wrong responses to the environment (wrong diet, no physical activity, smoking, drinking etc.) have been associated with a large number of human cancers, mainly due to reductions in expression of DNA repair genes (as in breast, colorectal, ovarian, head and neck cancers) but also in increased expression of growth genes (or lower expression of genes coding for proteins that slow cell growth). Higher stress response, anxiety, depression, cognitive impairment, obesity, osteoporosis, cardiovascular problems caused by altered endocrine (hormone) and immune response have also been shown to be the result of an improper epigenetic mechanism.

Some of such changes are also transmitted to the following generations.

But how does that happen?

Heredity of epigentetic changes. It was thought that mechanism of blocking/unblocking of genes would get undone when fertilization of the mother’s egg by the father’s sperm happens so that whatever the parents had done, eaten or lived through would not get passed onto the next generation. There is now evidence that certain parts of the DNA remain epigenetically marked and passed onto the prole, carrying information derived from habits and behaviour of the parents.

For example, parents can pass onto their children the predisposition to some mental illness, like depression and anxiety if they have been exposed to traumatic shock as children that changed the expression of certain of their own genes. This is the type of results that was found in adult children of people who survived the Holocaust, certainly a source of tremendous trauma that was passed onto the next generation as extreme sensitisation towards stressful or dangerous situations.

However, more common situations like over-drinking, smoking, eating obesogenic food carried out later in life as an adult are also passed to the prole. “The epigenetic changes are occurring every day, through what we eat, what we drink and how we behave,” as epi-genetists say.

However, the good news is that changes that happen in the DNA are not permanent but can be undone in the course of a lifetime, if external conditions change or if the person acts consciously in changing his/her inherited behaviour.

Furthermore, specific food can help repair DNA damage due to environmental attacks. DNA sequence damages are very frequent, occurring on average about 10,000 times a day (!) per cell of the human, and are caused by toxins, radiation and other aggressors. These damages are largely repaired, but some changes can remain. However, some food components epigenetically increase the levels of DNA repair enzymes, while other food components can reduce DNA damage, such as soy and bilberry.

Specific nutrients (i.e. vitamin Bs) support DNA integrity and can help protect from epigenetic damage:

sesame seeds, pumpkin seeds, Brazil nuts, yeast, liver, spinach and other leafy vegetables, soy, chicken, eggs, broccoli, garlic, wine

contain molecules that directly intervene on the DNA and the epigenome to protect them from harmful changes.

Food can also reverse some serious disease. For example, gene expression in the prostate causing cancer can be modulated by nutrition and lifestyle changes.

So being watchful of what we eat, not smoking, not drinking heavily will keep us away from troubles by not exciting genes that carry bad karma to us, our children and their children.

References

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Hooper, r. 2006 Men inherit hidden cost of dad’s vices, New Scientist, 4-1-2006

Jaenisch R, Bird A. 2003 Epigenetic regulation of gene expression: how the genome integrates intrinsic and environmental signals. Nature Genet 33: 245–254.

Learn.Genetics, Genetic Science Leanring center, in: <http://learn.genetics.utah.edu/content/epigenetics/>

McGowan PO, Sasaki A, D’Alessio AC, Dymov S, Labonte B, Szyf M, Turecki G, Meaney MJ. 2009 Epigenetic regulation of the glucocorticoid receptor in human brain associates with childhood abuse. Nat Neurosci 12: 342–348, 2009.

Meaney MJ, Szyf M. Environmental programming of stress responses through DNA methylation: life at the interface between a dynamic environment and a fixed genome. Dialogues in ClinicalNeuroscience 2005; 7:103–23.

Murgatroyd C, Patchev AV, Wu Y, et al. 2009 Dynamic DNA methylation programs persistent adverse effects of early-life stress. Nat Neurosci. 2009;12(12):1559–1566

Roth TL, Lubin FD, Funk AJ, Sweatt JD. 2009 Lasting epigenetic influence of early-life adversity on the BDNF gene. Biol Psychiatry. 65(9):760–769

Shonkoff, J.P., Andrew S. Garner, and THE COMMITTEE ON PSYCHOSOCIAL ASPECTS OF CHILD AND FAMILY HEALTH, COMMITTEE ON EARLY CHILDHOOD, ADOPTION, AND DEPENDENT CARE, AND SECTION ON DEVELOPMENTAL AND BEHAVIORAL PEDIATRICS 2012The Lifelong Effects of Early Childhood Adversity and Toxic Stress, Pediatrics129;e232

Spinney, L. 2010 Born scared: How your parents’ trauma marks your genes, New Scientist, 24/11/2010

Sun-weI Guo 2009 Epigenetics of endometriosis Mol. Hum. Reprod. 15, 10, 587-607

Thomson, H. 2015 First evidence of how parents’ lives could change children’s DNA, New Scientist, 4 June 2015

Wikipedia, 2015, https://en.wikipedia.org/wiki/Epigenetics

Zhang Xiang, Shuk-Mei Ho 2011 Epigenetics meets endocrinology J Mol. Endocrinol. 46, R11-R32

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