You are what you eat?

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We all know that our environment affects our health and well being. Breathing polluted air results in respiratory problems, being out in the sun too long results in sunburn, not having enough sunlight can result in seasonal-affective disorder, exercising improves cardiovascular health….the list goes on.

Researchers like to know why and how the environment can control our bodies and cellular functions. What we know now, is that some people are genetically programmed or predisposed to react to environmental cues.

This is most commonly observed in the case of cancer risk, and a well known example is the influence of diet on colorectal cancer (CRC) risk. World wide, CRC is the 3rd most common cancer in men and the 2nd most common cancer in women. In Australia, CRC was the cause of death for 1.1% of the males and 1.12% of the females who died in 2015.

CRC has a high hereditary factor, where a family history of CRC is a greater predictor of a person’s risk for developing the disease. CRC most often arises due to mutations that disrupt normal cellular processes. Commonly, these mutations can be found in genes that encode for molecules that repair DNA following exposure to damaging agents.

The good, the bad, the ugly.

So, how does diet influence risk if we know that there are hereditary risk factors? In order to discuss this, I want to share a quote that appeared in my social media news-feed the other day:

‘Eat bad food and bad genes are activated. If the same person, with bad genes activated from bad food, eats good food……those bad genes turn off and good genes turn on. Genes don’t control anything, they react to our environment…..mostly our food choices…… The “genetic causation of disease myth” is intended to make sure the public never understands that their food choices control the way their genes express themselves’.

There are so many problems with this statement. First, let’s start with ‘bad genes’. Is there such a thing? No. Genes exist because they produce molecules (proteins) that cells need.

Sometimes, a mutation can occur that can alter the function of the gene or of the proteins it produces. In a sense, it could now be a ‘bad gene’ but, eating ‘good food’ cannot turn off a ‘bad gene’. It is possible that the author of this post is confusing epigenetics with genetics. Epigenetics, as I have discussed previously, is the alteration of gene expression without changing the DNA sequence, and can be influenced by external factors such as diet. It is also possible that the author is confusing physiological effects with the genetic effects. An example of this could be the development of Type II diabetes due to obesity, where the body stops reading cues in regards to glucose production and consumption. But it is important to remember that this is also controlled by genes!

There is control, and then there is controlling.

Second, ‘Genes don’t control anything, they react to our environment. This simply is not  true. Genes control everything. However, in turn, genes can be influenced by other factors, which changes how they affect or ‘control’ cellular processes. If we come back to the epigenetics thread, the change in expression of gene can be altered by diet, but the alteration induced by the diet influences the expression of another gene producing the epigenetic change. Therefore, genes are still controlling expression!

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CRC risk is influenced by both genetics and environment.

Finally, the last statement ‘The “genetic causation of disease myth” is intended to make sure the public never understands that their food choices control the way their genes express themselves’. This brings us back to the CRC diet-associated risks, where genetic predisposition can be enhanced by diet. In this sense, diet increases the risk of developing CRC in predisposed individuals, but is not the cause. Someone following the guidelines for ensuring good bowel health, who doesn’t smoke, exercises daily and eats plenty of  ‘good foods’ as the author of the post suggests, could still develop CRC due to the familial risk.

 

Final Thought

Massive genome sequencing studies have demonstrated that there are untold gene-environment connections that can influence cancer risk and other physiological alterations. However, as not everyone has cancer (as an example), it is obvious that it needs to be the right ‘mix of ingredients’ to initiate the disease. For example, studies are now showing that gut microflora can influence predisposition to disease!

Humans have evolved, and this means alterations to genes, in response to the environment, but the genes have also influenced how we respond to these environmental cues!

 

Sources

http://www.sciencedirect.com/science/article/pii/S154235651630859X

Statistics obtained from the Australian Bureau of Statistics and the World Health Organisation

http://users.unimi.it/dmora/materiali/ANU2012/ClonRecCancer.pdf

http://journals.plos.org/plosgenetics/article?id=10.1371/journal.pgen.1004228

http://journals.plos.org/plosgenetics/article?id=10.1371/journal.pgen.1003284

http://www.sciencedirect.com/science/article/pii/S1550413115003368

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