Nature vs nurture; it is an age-old debate that attempts to answer the question of whether it is our genes or our environment that ultimately dictates our health, weight and therefore our destiny.
We have all heard things like;
- ‘well, they are just genetically gifted’
- or ‘he is so lucky that he can eat like that; it must be his genes’
- or ‘I will get cancer whether I smoke or not…’
But how true is this? Can our environment actually affect the way our DNA is expressed?
Genetics versus environment
According to psychologists, our environment and our genetic makeup affect the way we develop as human beings. Environment refers to anything we are exposed to after birth so things like parenting, education, nutrition, stress etc etc.
Genetics, on the other hand, refers to our gene makeup whose role is to signal the growth and development of our body. It is something that, until recently, we believed we had no control over.
Now, this is true to a certain extent, i.e. factors such whether we are male or female or have blue or brown eyes are pre-determined by the phenotypic expression of the DNA from our parents.
But does it end there?
Nature vs Nurture vs Nutrition
It would seem not; modern science is suggesting that we are not merely a result of our genes which we can do little to change. Our phenotype, or observable characteristics, can be determined by both genetic make-up and environmental influences.
It has further been shown that there are several diseases that can be affected by both genetic and environmental factors. For example, Type 2 diabetes, cancer, coronary heart disease and even Alzheimer’s are influenced by lifestyle and our nutrition plays a key role in this.
An excessive consumption of calories and lack of dietary nutrients significantly increase the likelihood of inflammation in the body occurring. It is this inflammation that causes chronic disease. So, if you are a person who is already genetically pre-disposed to cancer, let’s say, then a poor nutrition regime could tip you over the balance.
The link between nutrition and disease cannot be disregarded. The diet we choose can also have a significant impact on our outward characteristics.
Epigenetics is a new field of research that looks at how our environment affects our genes. Whilst it is in its infancy, it is certainly exciting!
For example, scientists have identified a gene called FTO. This is a gene that can predict fat mass and obesity; people with it have been shown to have dis regulated grehlin which is the hormone that regulates our hunger. This basically means that people with the FTO gene take longer to feel satisfied when eating.
Does this automatically mean that they will develop obesity? Well no. If the environment they immerse themselves in doesn’t easily lead to overeating then they can maintain a healthy weight. The issue, of course, is that our modern environment is saturated with overly processed, calorific foods that do little to fulfil our hunger. If, however, this is managed appropriately, a person with the FTO gene can have more control over their health.
Epigenetics looks at how our lifestyles can affect our DNA. It is showing that we have more control than we may think.
It would also seem that we have some control over the genes we pass on. According to Laker et al (2013), if a pregnant mother gains excess weight during gestation then her child could experience metabolic dysfunction in later life.
A higher birth weight has, therefore, been directly linked to a higher BMI in later life. In fact, children born to mothers with Gestational Diabetes are 1.4 times more likely to develop obesity for every 1kg increase in birth weight. This makes them more susceptible to Type 2 Diabetes .
Again, however, it comes down to nature versus nurture. Whilst a person may be more predisposed to obesity and disease because of maternal nutrition, this does not mean it cannot be avoided. If they can control their calorie intake and maintain physical activity then they can mitigate this risk. Now, I am not saying that it will be as easy for them as a person whose DNA is more favourable in this instance but it certainly can be managed.
A mother’s nutrition in pregnancy can have a significant impact on her child’s future health outcomes
What do the studies say?
There have been some very interesting studies conducted in twins that demonstrate this.
The Minnesota Twin Study , in particular, provided some amazing results. This famous study took sets of identical twins and overfed them by 1000 kcals a day for 6 days out of 7 over a total of 100 days. The weight gain amongst the group ranged from 9-30 lbs. BUT the weight gain within each pair was very similar whereas the weight between twins varied by up to THREE TIMES as much. Furthermore, the gain in visceral fat between the pairs was six time greater than that observed within pairs.
This highlights how genetics do play a role but environmental factors, i.e. diet, can be much more powerful in dictating our health outcomes.
Another interesting study carried out in child twins tested the theory that childhood nutrition is defined by environment rather than genes. It concluded that:
‘Shared environmental influences are the predominant drivers of dietary intake in very young children, indicating the importance of factors such as the home food environment and parental behaviors.’
It would seem, then, that adequate nutrition is the most effective way to prevent obesity and chronic disease. This has significant economic implications; preventing disease through a healthy diet is a much more cost effective than pumping millions of pounds in to pharmaceuticals and reactive health care.
Twin studies are a powerful way of gathering more information and evidence about the role of genetics and environment on health.
Another intriguing area of research is that relating to Ancestral Health. Whilst we cannot make any causal conclusions in this area as it is all observation, it is interesting to note that whilst many non-Westernised societies do not follow what we would deem an ‘optimal’ diet, they are relatively free from disease.
For example, the Kitavans of Papua New Guinea have a diet that is very high in carbohydrate and saturated fat yet they have very low rates of heart attack, stroke, diabetes and disease. Their carbohydrates are, however, sourced from yam, sweet potato, cassava etc and their fat intake comes from coconut which is very different to the composition of the Western diet. Whilst their high levels of triclycerides and low HDL levels would be strong markers of disease within our society, they do not suffer. Could this be because of the absence of processed carbohydrates and fats? They are also very active and source their own fresh food.
The Maasai Tribe have a very high fat and protein intake, mainly from milk, meat and blood, and rarely eat vegetables yet they have very low levels of serum cholesterol and no evidence of heart disease. They have been found to have a gene that is linked to lower cholesterol levels but again, is the lack of processed foods alongside a more active lifestyle a contributing factor?
Perhaps even more interesting are the Pima Indians of Arizona. They traditionally had ate ‘off the land’ and experienced little ill health. When they were affected by irrigation in the 19th Century, the could no longer grow their crops and became reliant on cheap, imported food from America which consisted of refined flours, sugar and hydrogenated fats. Sadly, they no have the highest rates of diabetes and obesity of any other population.
So, what does this say about genes and environment? Well, it would seem to suggest that our genetic make-up is affected by our ancestry; the society in which our mothers and fathers were born. It also would seem to suggest that we thrive in the environment that is optimal for us. Our environment has dramatically changed over the last century and as a result, lifestyle related diseases and obesity have increased.
When diet and lifestyle fit optimal health, they can over ride genes linked to diabetes and obesity.
What is a ‘healthy diet’?
Dietary adequacy is often all that is needed for physical health to be realised but genetic tendencies combined with a Western diet can often undermine this. This is evident in the light of our modern obesity epidemic.
If, however, you can stick to the following themes, then you are well on your way to living a longer, happier and healthier life:
- limit your intake of processed foods;
- reduce certain processed fats (i.e. trans fats);
- limit added sugar;
- limit refined sugar;
- focus on whole grain foods with or without the addition of lean meat.
Of course, life is all about balance and enjoyment but adhering to these principles 80% of the time can have a huge impact!
A healthy diet and active lifestyle can do much to counteract genetic predispositions
The key message is that you are more in control of your health than you may have been led to believe. Don’t believe you are a victim of genetics or that it ‘just runs in your family’; yes, they play a part but our life choices can have the final say.
Health is multifaceted; neither genetics nor environment alone can explain its course. Instead, look at nature vs nurture as a continuum; the lifestyle choices you make can move you closer to or further away from optimal health and disease.
This Blog was brought to you by Rebecca Flannery of Transformational Nutrition.
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