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Dr Caroline Leaf, behaviour and genetic destiny

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Today on her Facebook feed, Caroline Leaf posted a quote which said, “Your behavior can and does dictate your genetic destiny”. Dr Caroline Leaf is a communication pathologist and a self-titled cognitive neuroscientist. In isolation, it sounds like she has found confirmation of her view that our thoughts and behaviour control the physical properties of our DNA (Leaf, 2013, p35).

However, I wanted to look at the quote in a broader context, because in the broader context, the quote still doesn’t confirm Dr Leaf’s teaching.

The quote comes from an American doctor, Sharon Moalem. Dr Moalem is obviously a smart man. According to Wikipedia, “Dr. Moalem is an expert in the fields of rare diseases, neurogenetics, and biotechnology. He is the author of the New York Times bestselling book ‘Survival of the Sickest’ and ‘How Sex Works’. Moalem has cofounded two biotechnology companies and is the recipient of 19 patents for his inventions in biotechnology and human health.” (http://en.wikipedia.org/wiki/Sharon_Moalem)

It’s not that Dr Moalem’s quote is wrong. In the book from which the quote is taken, Dr Moalem discusses the expression of genes (Moalem, 2014). There is no doubt that our behaviour affects the expression of genes. For example, when the body encounters a high level of dietary iron (ie: we eat a big juicy steak), a series of steps activates a gene to promote the production of ferritin, a protein that helps to carry iron in the blood stream (Strachan and Read, 2011, p375-6). These changes in genetic expression are mostly protective (for example, ferritin is used to keep toxic elemental iron from damaging our tissues). There are some behaviours that will override the body’s protection, for example, excessive exposure to UV radiation will eventually lead to skin cancer. But overall, the changes in genetic expression that our behaviour causes are protective, and do not adversely affect our health.

Unlike Dr Leaf, Dr Moalem does not promote the notion that our behaviour changes the genes themselves. Neither does he promote that our behaviour, in isolation, is the only modifier of our genetic expression. The quote that Dr Leaf used came from the second chapter of Dr Moalem’s book, “Inheritance: How Our Genes Change Our Lives, and Our Lives Change Our Genes”. Really, the title says it all. Our behaviour influences our genetic destiny, but our genes influence our behaviour just as much, if not more.

For example, small variations in the genes that code for our smell sensors or the processing of smells can change our preferences for certain foods just as much as cultural exposure. Our appreciation for music is often changed subtly between individuals because of changes in the structure of our ears or the nerves that we use to process the sounds. The genetic structure of the melanin pigment in our skin changes our interaction with our environment because of the amount of exposure to the sun we can handle. Our genetic destiny is also largely influenced by our environment, most of which is also beyond our choice (Lobo and Shaw, 2008).

So your behaviour can and does influence your genetic destiny, but your genetic destiny is more influenced by our genes themselves, and the environment that is beyond our control.

Dr Leaf’s quote doesn’t look quite so supportive after all.

References

Leaf, C.M., (2013) Switch On Your Brain : The Key to Peak Happiness, Thinking, and Health, Baker Books, Grand Rapids, Michigan

Lobo, I. & Shaw, K. (2008) Phenotypic range of gene expression: Environmental influence. Nature Education 1(1):12

Moalem, S., (2014) Inheritance: How our genes change our lives and our lives change our genes, Grand Central Publishing, New York.

Strachan, T. and Read, A., (2011) Human Molecular Genetics. 4th ed. Garland Science, New York.

Dr Caroline Leaf and the genetic remodelling myth

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We are all slowly mutating!

Yep, it’s true. Not to the same extent as you might see in shows like X-Files or Dr Who, but still, our DNA is slowly accumulating permanent changes to the pattern of the genes that it contains. Thankfully, it’s only in science fiction that the mutations result in zombie apocalypse scenarios.

Dr Caroline Leaf is a Communication Pathologist and a self-titled cognitive neuroscientist. Still glowing from the unquestioning adulation of her faithful followers at the Switch On Your Brain conference last week, Dr Leaf has hit social media again. Most of her posts have been innocuous quotes that look borrowed from Pinterest, but today, Dr Leaf has ventured into the pseudoscientific again by claiming that, “Our genes are constantly being remodeled by our response to life’s experiences.”

Unless your response to life’s experiences is to stand next to an industrial microwave generator or live in a nuclear waste dump, Dr Leaf’s statement is pure fiction. Dr Leaf confuses the mutation of our genes with the expression of our genes.

The only way our genes actually change is through mutation. A mutation is a permanent change in the sequence of the DNA molecule. A genetic mutation is a permanent change in the DNA sequence that encodes a gene. DNA is constantly mutating, because of environmental damage, chemical degradation, genome instability and errors in DNA copying or repair [1: p97]. Still, the actual rate of DNA mutation is about 1 in 30 million base pairs [2]. So DNA is very stable, and changes for a number of reasons, only some of which are related to our external environment. And as I alluded to just before, slightly tongue-in-cheek, our responses are not the main contributor to these environmental influences, unless we deliberately expose ourselves to ionizing radiation or smoke cigarettes. Our DNA does not change because of our thought processes as Dr Leaf advocates [3].

What does change more readily is the expression of those genes. Gene expression is the cell machinery reading the genes and making the proteins that the genes encode. The genes are expressed to make the proteins needed for the cell to maintain its function. Which genes are expressed is dependant on the cell’s stage of development and the environment it finds itself in. For example, when the body encounters a high level of dietary iron, a series of steps activates a gene to promote the production of ferritin, a protein that helps to carry iron in the blood stream [1: p375-6]. Gene expression isn’t solely dependent on our environment though, because an embryo is expressing genes like crazy in order to make the proteins to build a human being, but the gene expression in an embryo is largely following a pre-determined time course, not the environment [4] (and certainly not because of responses to life’s experiences).

In summary, our genes are controlled by a myriad of different factors, nearly all of which have nothing to do with our responses or choices. Our genes are not changed by our choices or our responses. Our genes may be mutating, but God designed our cells with mechanisms to repair them. Our genes are not being remodelled by our responses. That’s the realm of science fiction.

References

  1. Strachan, T. and Read, A., Human Molecular Genetics. 4th ed. 2011, Garland Science, New York, USA:
  2. Xue, Y., et al., Human Y chromosome base-substitution mutation rate measured by direct sequencing in a deep-rooting pedigree. Curr Biol, 2009. 19(17): 1453-7 doi: 10.1016/j.cub.2009.07.032
  3. Leaf, C.M., Switch On Your Brain : The Key to Peak Happiness, Thinking, and Health. 2013, Baker Books, Grand Rapids, Michigan:
  4. Ralston, A. and Shaw, K. Gene Expression Regulates Cell Differentiation. Nature Education, 2008. 1(1): 127; http://www.nature.com/scitable/topicpage/gene-expression-regulates-cell-differentiation-931

Like to read more about Dr Leaf’s teaching and how it compares to current science? Download the free eBook HOLD THAT THOUGHT, Reappraising The Work Of Dr Caroline Leaf