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What You Need To Know About Genetics and Chronic Illness

Are you chronically ill and have been told that it’s genetic and there’s nothing you can do? Do you, like most people, believe that your genes are your destiny and there is simply nothing we can do to change this?

While these beliefs still seem to be prevalent, research has shown that this is not strictly the case.

Sure, our genetic sequence cannot be changed but the truth is that gene expression can indeed be influenced by our environment, which includes the diet we eat and the lifestyle behaviours we engage in.

This knowledge gives hope that we do actually have some power over our genetic destiny.

What are Genes?

DNA is the basic code for life present in nearly all of our cells.

The role of DNA is to code for amino acids, the building blocks of protein, which are essentially the building blocks of the body. The sequence of amino acids defines what protein is being made.

A gene is the small sequence of DNA coding for a single protein. Different forms of genes are called ‘alleles’ and there’s a pair of alleles for each gene. The unique combination of alleles determines our physical traits and characteristics.

After a protein has been built, it can go through other modifications not directly influenced by genes (e.g. attachment of carbohydrates, phosphate or methyl groups, or forming a complex with metals). This affects the function of the protein.

Genetic Mutations

A genetic mutation is a change occurring in a DNA sequence, which may result in a change of the shape and function of the protein produced from the mutated gene. This can be good or bad.

DNA mutations play an important role in evolution as they contribute to the adaptation to an ever changing environment.

For example, we normally lose the ability to make lactase (the enzyme that digests the milk sugar lactose) but in areas of the world where dairy has been a staple of the diet for a long time, mutations in the lactase gene have occurred so that some populations are still able to produce the enzyme later in life. Dairy consumption was not common in parts of Asia, which is why more Asians are lactose-intolerant (i.e. they lack the enzyme to digest lactose).

Other reasons why mutations can occur are mistakes that occur when the DNA is copied or environmental factors such as radiation and cigarette smoke. However, cells have the ability to recognize damage that may cause a mutation and repair it. But sometimes repair doesn’t happen and this can contribute to diseases like cancer.

As you can see, some mutations can happen during our lifetime, but many of them can be inherited.

The most common types of genetic variations are Single Nucleotide Polymorphisms (SNPs). They are variations of a single base (A, C, G, or T) within a specific gene. They may not lead to a change in function of the protein coded, or they could up- or down-regulate it.

Genetic Mutations and Chronic Illness

I think we generally think of scary diseases when we think of genetic mutations. But actually, a lot of mutations are ‘silent’ as they don’t affect the final structure and function of the coded protein.

In fact, only around 5% of mutations result in genetic diseases. This happens when the function and structure of a coded protein is significantly altered.

Here are the main types of genetic diseases:

  1. Chromosome Disorders

These occur when there are changes to the number or structure of chromosomes. For example, an extra chromosome leads to Down’s syndrome.

  1. Single Gene Disorders

These are caused by a defect in a single gene that are inheritable. Again, there are different types of diseases (there are others but I’ll just list the more ‘common’ ones):

  • Dominant: Disease occurs when a person has one altered copy and one normal copy of a particular gene and the altered copy is dominant. Examples are Huntington’s disease and achondroplasia.
  • Recessive: Disease occurs when a person has two altered copies of a relevant gene. It can be inherited if both parents have one altered copy (this is why incest is more likely to result in offspring with genetic disorders). Examples are: Cystic fibrosis and sickle-cell anaemia.
  • X-linked: Disease occurs when an altered gene occurs on the X chromosome. This is more likely to occur in men as they only have one X chromosome. Examples are: muscular dystrophy and Turner syndrome.


  1. Multiple Gene Disorders

All other chronic diseases that have a genetic component are caused by the interaction of several genes as well as our environment. Because of this, these are the types of mutations that do not necessarily lead to disease. Examples are: Autoimmune disease, allergies, cancer, IBS, heart disease and many more.


The literal meaning of epigenetics is: ‘upon genes’. It is the study of changes in the expression of genes without an alteration to the actual DNA sequence.

This can be seen as an ‘on- or off-switch’ for specific genes.

This is mostly regulated by the attachment of certain organic compounds (methyl and acetyl groups) to DNA.

This basically ‘marks’ a part of the DNA sequence so that it’s not transcribed anymore and therefore ‘switched off’.

Our environment has a huge impact on this process, thereby influencing gene expression (whether a gene is switched on or off). The position of the ‘marks’ on the DNA sequence can change over a lifetime.

Epigenetic changes can be inherited over generations but this doesn’t mean that they can’t be changed back. An example I have often heard is that children born mothers that experienced food scarcity during pregnancy are more likely to gain weight as they are epigenetically predisposed to storing calories better. This is because they were born into an environment of potential food scarcity and this epigenetic change would help them survive longer in such an environment.  However, whether they actually become overweight depends on their own environment.

The Microbiome

I’ve talked about the microbiome before. We are hosts to trillions of microbes living in and on our bodies.

These microbes come with their own genes. The gut microbiome alone comprises of over 3 million genes – this is a lot more than the human genome (23.000)!

Microbes can do a lot of good things for us (as well as bad). You can read more about the topic in this article. The genes of the microbiome therefore also have an impact on our health and should not be forgotten about when we think of genetics and chronic illness!

Conclusion: Genes and Chronic Illness

Hopefully the above has given you a better understanding of what role genes actually play in chronic illness. I think all too often people might be told that their conditions are genetic, when this may not be strictly the case.

If you’re one of those people with a rare single-gene disease I’d like to say that I don’t know a lot about this topic and I think that those cannot be changed and are, in fact, purely genetic (but maybe quality of life could be improved by diet and lifestyle changes?!).

But for those suffering from a multiple gene disorder there is hope. The gist is that genes in those cases predispose us to what illness we might develop but this doesn’t mean that we will actually develop them. However, the more predisposing genes an individual has, the higher the chances of developing illness.

Diet, lifestyle and environment play a huge role here. For example, autoimmune diseases develop through the interaction of 4 major factors:

  • Genetic susceptibility
  • A hyper-permeable gut (leaky gut)
  • Environmental triggers, infections, stress etc.
  • Diet and lifestyle

Once an individual has developed an autoimmune disease, they can develop others if they have the genetic susceptibility.

For example, I have SNPs that predispose me to autoimmune thyroid disease, IBD, type-2 Diabetes and obesity. I have developed Hashimoto’s (without knowing the exact trigger) but none of the others. I credit my healthier-than-average upbringing.

Someone with the same SNPs but brought up on a fast food diet may have had a totally different fate.

From this you might understand why it is also very hard to find a ‘cure’ for multi-factorial diseases – one pill simply can’t address all the different factors playing a role!

While we can’t change our genes we can change how they are expressed.

We can change our diet, lifestyle and environment.

And we can modulate our microbiome.

There is hope!

What are your thoughts on genes and chronic illness? Let me know in the comments!

Pin it for later:


BioCare Nutrigenomics in Practice 2018

Wellcome Genome Campus Your Genome

Bellantyne, Sarah The Paleo Approach (Las Vegas: Victory Belt Publishing, 2013)

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