Do we make choices on the basis of our own conscious reflection? Are we personally responsible for our path in life? Are we the masters of our destiny? Or – do our genes make us do it? MAXIM’s resident Clinical Nutritionist, BROOKE BENSON CAMPBELL (BHSC Nut Med) investigates…
Flash back to 1979. Two identical twins, Jim Springer and Jim Lewis, were reunited at age 39, after being separated as one-month-olds and adopted by different families. They found, when comparing stories, that both had married and divorced a woman named Linda and remarried one named Betty. Both had interests in carpentry and mechanical drawing, smoked Salem cigarettes, drove pale-blue Chevrolets, found spelling difficult and had worked as part-time deputy sheriffs. Both also named their first son James Alan, and their pet dogs ‘Toy’. The basis of their identities seemed to be written in their genes.
Some of us may find this story disturbing. We like to think that we are the masters of our destiny, that we make choices on the basis of our own conscious reflection, that we are personally responsible for our path in life, that the future is ours to shape. And yet does this story prove our final decisions are already pre-programmed in genetic code? Is ‘my genes made me do it’ a viable get-out-of-jail-free catch-cry?
Nearly 100 years ago, Freud wrote that ‘biology is destiny’ but when we consider the latest discoveries in the field of epigenetics and behavioural science, is this still accurate? In the nature versus nurture debate, who emerges triumphant? Let’s walk the genetic plank to answer the age-old question: do our genes govern our fate?
When we learned about genetics at school, it seemed fairly straightforward – for every feature there existed a gene: one for eye colour, one for hair texture, one for skin tone and so on. We inherited two copies of each gene (one from each parent) and the dominant allele would govern the resulting feature. It was a simple time, before Netflix, gluten-free bread, iPhones, exotic superfoods and Trump. Fast-forward a few decades: while eating our smashed avo on GF toast as we scroll through Instagram slurping on our Matcha Latte and embracing the presidential Twitter feed, we come across an advertisement for a salivary test that analyses gene ‘SNPs’ and promises to provide insight into unique personality traits, academic potential and lifespan – all for just $300. So, is this testing the modern equivalent of a crystal ball or a scientific exploration into the future?
To determine the answer, we need to start by understanding the science of epigenetics. Epigenetics (which means “over or above genetics”) is turning what we’ve long held true about biological destiny and genetic predisposition upside down. Previous studies, based largely on studies of twins, have suggested that many of our traits are more than 50% inherited and based in DNA – these include obedience to authority, vulnerability to stress and risk-taking behaviour. Another historical study of more than 800 sets of twins in the United States found that genetics were more influential in shaping key traits than a person’s home environment or surroundings. Although it remains true that our DNA – our genetic code – provides the blueprint for our physiological makeup, recent studies have discovered that there is something else that is controlling each and every gene – the epigenome.
While epigenomes do not change the DNA, they sit on top of each genome and direct the genes to turn on or off depending on environmental changes or biological triggers. In simple terms, if the DNA is the hardware, the epigenome is the software. Windows can be loaded onto a MAC – the computer chip stays in place (the same genome) but the software can be altered. This new discovery means that your inherited genetic heritage is not the primary determinant of your health, illness risk or longevity. In short, your genotype is a predisposition, not a prediction. It is this discovery that may be able to help explain certain scientific mysteries: why can one member of a pair of identical twins develop asthma when the other is fine, why autism strikes boys four times as often as girls, or why extreme changes in diet over a short period could lead to extreme changes in longevity.
While epigenetics sounds complex, one of the ways it alters the genome is fairly simple. Researchers have found that when a single methyl group (one carbon atom attached to three hydrogen atoms) fastens to a specific spot on a gene, it can change the gene – turning it on or off. In 2003, Duke University oncologist Randy Jirtle displayed the potential effect of DNA methylation in a groundbreaking experiment. He started with a pair of fat yellow mice known as Agouti mice (the Oompa Loompa of the rodent kingdom), so called because they carry the Agouti gene, a particular gene that in addition to making the rodents yellow and giving them an increased appetite, also makes them prone to cancer and diabetes). Jirtle and his team separated the mice into two groups and fed one group of pregnant Agouti mice a diet rich in B vitamins (folic acid and Vitamin B12).
The other genetically identical group were not given any prenatal nutrition. The parent mice fed the diet high in methyl-rich B vitamins produced mice that were slender and mousy brown, rather than fat and yellow. They did not display their parent’s susceptibility to cancer and diabetes and lived to old age. The effect of the Agouti gene had been virtually erased, without DNA change, and with diet. When examined, it was discovered that the mothers had passed on the Agouti gene but thanks to their methyl-rich pregnancy diet, they had added a chemical switch (an epigenome) to the gene that squashed its negative effects.
The researchers had proven that nutritional change in the diet of mothers could affect the gene expression of their children. The message here – if you’re tall and thin, ring your mother to thank her… (no, its not quite that simple, but the fact remains: the diet of your mother while pregnant has already influenced the fate of your health span and longevity). OK, so your body may have been governed by mum’s eating habits, but surely your personality traits were been built in genetic stone at conception and cannot be tweaked?
Think again. In their famous research paper published in 2004, Doctors Moshe Szyf and Michael Meaney proved something incredible: epigenetic programming was also possible after birth and could be changed by maternal behaviour. It’s Mum’s fault (again…). Meaney compared two types of rats: those who patiently licked their offspring to nurture them after birth and those that neglected their newborns. The licked newborns grew up to be comparatively brave and relaxed (for rats). The neglected newborns grew into nervous skittish rodents who ran for the darkest corner when placed in a new environment. The researchers then analysed the brain tissue of both the licked and non-licked rats and found different DNA methylation patterns in the brain cells of each group. Amazingly, the mother’s licking activity resulted in the suppression of a gene involved in stress response. Put simply, the mothers who were attentive and nurturing to their offspring changed their pup’s response to stress for life, making them calmer and as chilled out as a lab mouse can be, proving a little love goes a long way, and that while DNA remains the same, psychological and behavioural tendencies are formed by experience and epigenetics. You’ll never look at Mum the same way again.
To demonstrate that the effects of the experiment had no basis in genetics, the scientists took rat pups born to inattentive mothers and gave them attentive ones, and vice versa. As predicted, the rats born to attentive mothers but raised by neglectful ones grew up to be stressed and nervous, while those born to bad mothers but raised by good ones grew to be calm and brave, which also provides an interesting insight into the world of foster families and adoptive parents.
Worringly, another study has determined that this epigenetic change can last for several generations. Researchers exposed male mice to 10 days of bullying by larger, more aggressive mice, resulting in the bullied mice being socially withdrawn. They then took that group of bullied mice and bred them with females, but kept them from meeting their offspring. Despite having no contact with their fathers, the offspring of the bullied mice were hypersensitive to stress and had depressive tendencies. Inherited personality was altered through epigenetic change over generations. So far, the definitive studies have only involved rodents, but researchers are constantly finding evidence to suggest that epigenetic inheritance is at work in humans too. The environment and atmosphere of childhood can shape us forever, down to the epigenetic core.
Exposure to toxins and foreign chemicals can also work to alter our genetic expression. In 2004, geneticist Michael Skinner accidently discovered an epigenetic effect in rats that lasted at least four generations. He was studying how a commonly used agricultural pesticide, when introduced to pregnant rats, affected the sperm count of male pups. The surprise came when he tested the male rats in subsequent generations – the grandsons of the exposed mothers. Although the pesticide had not changed DNA coding, the second-generation offspring also had low sperm counts. The same was true of the next two generations. It turns out that you may not have your mother to blame for everything and a scroll through your ancestry.com family tree could provide the real villain of the genetic story.
Subjecting male lab rats to endocrine-disrupting chemicals has also produced behavioural effects in their offspring, even when the toxin exposure happens well before mating. Many studies have been done on the common chemical bisphenol-A (otherwise known as BPA) found in plastic water bottles and food storage containers. This chemical alters DNA methylation and appears to effect learning, memory and behaviour in the children of parents exposed. We also know that when male mice and rats are exposed to alcohol before mating, their offspring do badly at discrimination on spatial tasks, they are more aggressive and display more anxiety-like behaviour than offspring of unexposed animals. Males exposed to cocaine have offspring with smaller brains and deficits in attention span and working memory. In all examples, epigenetic changes have been noted. It may seem bizarre, but now the responsibility rests with YOU – what you eat, smoke or do today could affect not only your health, but also the health and behaviour of your great-grandchildren. The DNA may remain the same, but just as you have inherited your grandfather’s hairy legs and anxious-disposition caused by neglect he suffered as a baby, your grandchild may end up detesting the smaller brain and lack of attention span handed down through epigenetic changes caused by your habitual ‘weekend warrior’ behaviour. Stay in this Saturday night… not for you, but for your great-grandchildren.
More and more, researchers are finding that an extra bit of a vitamin, a brief exposure to a chemical, even an added dose of maternal love can alter the epigenome – and thereby change the software of our genes. Interestingly, we are discovering that even common health advice like exercising may work (at least in part) by affecting the expression of our genes. Certain types of stem cells can ‘choose’ how they differentiate, and exercise and environmental factors can actually determine the direction that cells take early in their development. When mice ran on a treadmill for as little as an hour three times a week, the exercise epigenetically encouraged these stem cells to become blood-producing cells of the bone marrow, rather than fat cells. The stem cells of the sedentary mice studied were much more likely to become fat cells, meaning that exercise has the ability to impact biology and epigenetics. It turns out that we are not completely at the mercy of our genes. In many ways, they are at the mercy of our health and lifestyle choices – we hold the power of genetic fate in our sweaty palm.
And brain power? Researchers have previously shown that a person’s IQ is highly influenced by genetic factors and have even identified certain genes that play a role. They’ve also shown that approximately 62% of individual academic performance has a basis in genetic factors… but it is not all about a Mensa-level IQ. A study of more than 6000 pairs of twins found that academic achievement is influenced by genes affecting motivation, personality and confidence (in addition to those that shape intelligence) and all of those genes are susceptible to epigenetic change. Regarding intelligence and work performance, it seems that epigenetics offers us a means to transcend our innate genetic tendencies – to change who we are and what we become.
As scientific research stands today, we appear to be a product of both nature AND nurture, a mixture of genome AND epigenome, of inheritance AND environment. When we make choices in life, those choices are shaped by our descendants, our surroundings, our beliefs and our genetic makeup. In some ways, we are shaped by forces beyond our control and in others we have the conscious power to determine our fate.
So, back to that salivary DNA test… Will it give you simplistic information about your ethnic ancestry? Yes. Will it shed light on personality, motivation and academic potential? Maybe. Will it provide a crystal ball that will allow you live your life knowing with certainty where/when/how you will live and eventually die? Not even close. As far as genetic certainty is concerned, there isn’t any – and that’s the beauty of it.
Brooke Benson Campbell (BHSc) is a Clinical Nutritionist and Naturopath, speaker, writer and presenter with a passion for all things health, beauty and wellbeing. A self-proclaimed human test subject, she is constantly trialing the newest products, seeking the latest discoveries and reading the current clinical studies, in order to share her findings with the public through private practice, social media and industry education.
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