Why genes are not the whole story for health

In recent years, there has been a lot of emphasis upon the genetic causes of disease, particularly the chronic diseases that are wreaking havoc upon older populations in the developed world, such as cancer, Alzheimer’s, Type 2 diabetes, cardiovascular disease, and others. The implicit promise of the Human Genome Project was that this would be a paradigm shift for medicine because the sequencing of the complete human genome would pave the way to understanding the root causes of diseases, and then it would be possible through genetic engineering to prevent or cure cancer and other ills.

Whilst this approach has merit, it is based on several assumptions. The first is that chronic diseases have a genetic origin; the second is that, even that is true, the ‘faulty’ genes are always expressed. Both assumptions are suspect. Let’s look at the first assumption: do chronic diseases have a genetic origin?

There was an interesting study in 2016 that looked at this very question. The researchers investigated 28 chronic diseases to estimate the incidence due to genetics versus what has been called the ‘exposome’. The exposome refers to the sum of all non-genetic exposures in an individual lifetime, starting from the moment of conception. It encompasses everything from the food we eat, to the water we drink, to the air we breathe, to the social interactions we have, to the lifestyle choices we make, even including the health of our parents at the time of our conception.

The researchers found that the genetic contribution to the onset of chronic disease ranged from 3.4% for leukemia to 48.6% for asthma with a median value of 18.5%. Cancers had the lowest genetic contribution (median 8.26%) while neurological (median 26.1%) and lung (median 33.6%) diseases had the highest genetic contribution. These genetic contributions were then linked with Western European mortality statistics to estimate deaths attributable to genetics for heart disease and nine cancer types. Of 1.53 million Western European deaths in 2000, 0.25 million (16.4%) could be attributed to genetics, plus the interaction between the genome and the exposome. In summary, this means that less than 20% of chronic disease can be attributed to the genome alone. Another way to put this finding is that ‘genes load the gun, the environment pulls the trigger’.

So, whether a person has a genetic predisposition to developing a chronic disease becomes less significant than the quality of their lifetime exposures; focusing on the exposome is by far the most important task when it comes to preventing chronic disease. Most of us don’t need to live in dread just because we had close family members who died of cancer or Alzheimer’s because we can all alter our environment to some degree, if we so choose. The important areas to work on are diet, physical activity, sleep and stress management. Let’s look briefly at each of these.

Whilst there are numerous commercially-promoted ‘diets’ that promise all kinds of unproven benefits, there is a lot of evidence that a well-balanced nutrient-dense diet that is aligned to our evolutionary heritage, is an excellent place to start. This means avoiding processed foods heavy on added sugar, unnecessary additives and unhealthy low quality fats.

Physical activity is fundamental to being human. Sitting for most of the day leads to week, injury-prone bodies that struggle to support us for the whole of our lives. See this previous article for more guidance.

We sleep less than our recent ancestors for many reasons. One is the plethora of artificial light and electronic stimulation that are generally see as a boon of modern life, but which can easily interfere with our circadian rhythms that have evolved for millions of years. It has become a badge of honour in modern culture to ‘get by’ on less sleep than everyone else. Whilst this is feasible in the short-term, there is a long-term price to be paid.

It sometimes seems as if we have deliberately designed our modern lifestyle to maximise stress. So many of us work eighty-hour weeks, perhaps at more than one job, with little time to unwind. See this article for more information about stress management.

The good news is that the choices we make every day are the most important factors in determining our future health and longevity. With the right knowledge and actions, we can change our lifestyle and behaviour to optimise our well-being.

What about you? Do you feel you have the knowledge to take responsibility for your health? Let us know in the comments below.











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