Is It Necessary to Express an Inherited Trait?

Posted 1/20/2014.

At the Allergies, Sinuses, Asthma, Autoimmunity & the Gut Workshop this past weekend, several participants asked about the role of genetics in the health problems they struggle with in their lives. This is an important issue so I decided to do some research into it.
We all inherit a variety of traits from our families – height, weight, eye color, intelligence, etc. And we also wonder if things such as our weight, digestive issues, skin problems, tendency toward depression and anxiety, alcoholism, cancer might also be genetically set and there’s nothing we can do about any of it.
The good news is that this seems not to be true. Now that scientists are discovering the important role our gut microbiota plays in our health, inheriting a tendency for a disease seems to carry less importance.
My mom died of stage 4 colon cancer in 2000. Ten days after her death, my dad collapsed and was found to have colon cancer too. He underwent surgery and did well for three more years. My father’s father had died of rectal cancer at a young age. I know of no history of GI cancer in my mother’s family. My parents had been married 58 years, consuming the same diet along with sharing their bacteria.
When my dad died in 2003, I was left with the task of settling his estate – a huge and complicated project. A year and a half later I’d worked my way through the bulk of the work, was exhausted and in serious need of rejuvenation so took myself to a yoga workshop in Costa Rica. While there, I also tried out a few types of massage therapies new to me. During one of them, the masseur mentioned the dark circles under my eyes. I said, “Oh, I inherited them from my mother. Her mother had them too so I assume they’re just genetic.” His response produced one of those life-changing moments:
“Those dark circles indicate an imbalance in your gut. Just because you inherit something doesn’t mean you have to let it be expressed.”

This whole Allergies and Your Gut site is about the relationship between our gut flora and various aspects of our health.
In The Gut Microbiome – Our Second Genome section, I talked about the 2-5 pounds of mutually beneficial microorganisms that make their home inside our guts. The majority of them are various bacteria, but there are also some fungi, protozoa, viruses, yeasts and primitive life forms called Archaea. These hard working components of our gut flora are actually little aliens – not manufactured by our bodies, not even human.
I also discussed how these microorganisms get into our guts – that our GI tracts are sterile while we’re in utero and we pick up our first dose of bacteria and the other gut flora organisms from our mothers as we pass through the birth canal. Once out in the world, we acquire additional microorganisms for our gut flora from what we’re fed, from other people around us, from pets in the home and from the environment.
So, if we acquire our mothers’ bacteria while we’re being born and then additional gut flora from our food, the environment, pets and other people (likely many who are not our blood relatives), then our gut microbiomes are operating only partially like our mothers’.
Here’s an example of how what’s in our gut flora can have a moderating effect on the development of disease:
The immune system must be able to discriminate between self and non-self or it would destroy anything entering the body. When this discrimination fails, the immune system starts attacking and killing cells and tissues in the body, causing autoimmune disease. White blood cells called regulatory T-cells play a central role in the suppression of inflammatory and allergic responses by preventing the excessive reactions of other immune system cells. (Wikipedia, 2014)

Japanese researchers found that butyrate, a compound produced by bacteria fermenting dietary fiber in the gut, can increase the production of these useful T regulatory cells (Yukihiro, 2013).
Scientists have been aware that butyrate has an anti-inflammatory effect and that many people with autoimmune conditions (approximately 100 have been identified so far) have impaired T regulatory function and high levels of inflammation. This study demonstrated a particular mechanism for how it works. (Kresser, 2013)
There are now many other examples showing how our gut flora influences our health:  heart disease, GI problems, gum and tooth disease, heart disease, Type 2 diabetes, allergies, asthma, obesity, yeast overrun infections, cancers, depression, skin conditions, urinary tract infections, ADD and ADHD, hormonal imbalances, pulmonary disease, Alzheimers, all the autoimmune diseases and many more.


We’re born with genes we inherited from our parents. Then the genes of the bacteria and other microorganisms living in our guts interact with those human, inherited genes. Remember that are bodies contain many more alien than human genes: The genes inside the microbes in our guts outnumber our inherited genes by a whopping 150-300:1. (Kresser, 2013); (Yukihiro, 2013)


If you’re at all interested in the relationship between your gut microbiota and your health, I highly recommend reading Kresser’s conversation with Jeff Leach, one of the founders of the American Gut Project. The subject of the interview is You Are What Your Bacteria Eat: The Importance of Feeding Your Microbiome.





In the interview, Jeff Leach (shown above gathering microbes samples in Namibia) also has this to say about the relationship between our gut bacteria and our health:

People’s general take on bacteria, which is still kind of a little bit of a hangover from the last 50 years, is that bacteria are bad, so we need to kill them through antimicrobial soaps and antibiotics, which, of course, save lots of lives, and on and on and on.  We’ve improved hygiene and sanitation and really changed things, but the other edge of that sword is that we may be changing the relationship of the microbes in such a way that this imbalance is a precursor or we’ve opened the pathogen’s door, if you will, to inflammation.  Now … it’s hard to be in the medical sciences now and not be thinking about how bacteria affect your particular field of study.  It doesn’t matter if it’s psychiatry.  It doesn’t matter if you’re a heart surgeon or if you deal with autoimmune disease.  Microbes are in there somewhere, and so now what everybody’s trying to do is to figure out what role microbes play in diseases as diverse as autoimmune diseases or obesity or other metabolic disorders like type 2 diabetes.


So it appears our gut microbes are actually more in charge than our inherited genes for much of what goes on in our bodies. Our human, inherited genes are set but the genes in our microbiota are somewhat mutable. If we can nourish our gut microbes well – and don’t kill them off with antibiotics, genetically modified foods, environmental poisons and the like – then it seems they can protect us from expressing any disease tendencies we inherited from our human families.



Kresser, C. (2013). RHR: You Are What Your Bacteria Eat: The Importance of Feeding Your Microbiome – With Jeff Leach. Health for the 21st Century. See

Wikipedia. (1/6/2014. Regulatory T Cell. See

Yukihiro, F. et al. (2013). Commensal microbe-derived butyrate induces the differentiation of colonic regulatory T cells. Nature, 501, 435–438. See


DISCLAIMER:  Nothing on this site or blog is intended to provide medical advice, diagnosis or treatment.

© Copyright 2013-2014 Joan Rothchild Hardin. All Rights Reserved.



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4 thoughts on “Is It Necessary to Express an Inherited Trait?

  1. See this interesting article by Robert Mercola, MD, on the topic of whether genetics or environment rule the body – whether a genetic predisposition must be expressed:

    Dr. Mercola
    September 30, 201

    From his post:


    * Government, industry, and scientists appear to be in collusion to hide the fact that everything from human health and intellectual capacity to various addictions are indeed caused by the environment in which we find ourselves.

    * A strong case can be made for the theory that our health science is in the grip of hidden political forces that stand to gain by promoting the idea that poor health and other life achievements are driven by genetic factors.

    * The science of epigenetics challenges the conventional view of genetics, proving that the environment determines which traits a gene will express, and that your fate is in no way written in stone even if you have genetic predispositions.

    * Your environment and lifestyle, particularly your diet, has a direct influence on your genetic expression. For example, research using identical twins have shown that diet trumps genes in terms of the level of health you achieve.

  2. Important question. I am by no means an expert on genetics or gene expression but my understanding is that the answer is “ABSOLUTELY NOT!”–we are not doomed by our genes, and many–if not most–of our genes possibly never get expressed.

    We inherent many genes, some in genotype, some in phenotype, some are dormant,
    some need environmental triggers to express, some need endocrine triggers to express, some need a combination of all kinds happening in a particular timing and environment and exposure to MAYBE be expressed.

    Genes expression “depends”–that unknown explains why having a gene, for say, breast cancer, does not mean you WILL have breast cancer. It may mean that your RISK is higher than the average, but it cannot say that you will surely get it. Or at what age, or at how aggressive it would be, etc. There can be two people with the same ‘breast cancer possibility’ genes, one who’d get breast cancer and another never will. Same with insulin efficiency, sensitivities and allergies, obesity, heart disease, PCO, and more.
    For the most part, genes are “possibilities.” Your whole family can be obese and you may not be–because maybe your life habits are different, maybe your diet and activity levels are different, what your mother ate during pregnancy may be different, what childhood illnesses you had, what antibiotics you may have received, how much stress you had, among other things.
    Only few (and most of those require a combination of genes, anyway) are almost certain to express, such as Tay Sachs Disease. They are a ‘different class’ of genes, which behave more ‘classically’ (a-la Mendel’s genetic rules).
    In general, I believe, we have quite a lot of control–conscious and otherwise–over whether and which genes are expressed.

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