Is IBS Genetic? What the Research Says About IBS Genes - Dr. Michael Ruscio, DC

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Is IBS Genetic? What the Research Says About IBS Genes

Some Genes May Influence IBS, But They Aren’t the Whole Story

Key Takeaways:

  • IBS likely arises from a combination of genetic, environmental, and possibly psychological factors [1, 2].
  • Having a family member with IBS increases your likelihood of having IBS [3, 4], but it’s also possible to develop IBS sporadically if it doesn’t run in your family [4].
  • Specific genetic abnormalities have been identified as possible contributors to IBS [2, 5, 6, 7, 8].
  • Since both environmental and genetic factors may contribute to IBS — and you can’t control your genes — it’s best to focus on the environmental risk factors that you can control. Doing so can still make a significant impact on your health.  
Damaged strand of DNA chain. Mutations and genetic diseases, cancer

There was a time not too long ago when we put a heavy emphasis on a person’s genome (their genetic code) to assess their risk of developing certain diseases and health conditions. When you were diagnosed with a condition, you were told that that was just the luck of the draw – your genes determined your health and there was no changing that. In many ways, we still subscribe to this belief. 

But we now know that environmental and even psychological factors have just as much if not more weight in the development of various health problems, from heart disease to intestinal conditions. 

The risk for developing IBS has a similar story: genetic predispositions do exist, but environmental and psychological factors also play a big role. However, the exact cause or causes of IBS are still unknown. It is likely that there are multiple causes, and each case may have a completely different story behind it.

The good news is some of those potential causes are within your control, such as your living environment and diet.  

In this article, we’ll answer the question “is IBS genetic,” and look at potential environmental, psychological/situational, and (epi)genetic causes. We’ll also offer some solutions to reduce certain risk factors like managing stress levels and optimizing nutrition.

Breaking Down the Potential Causes of Irritable Bowel Syndrome 

Irritable bowel syndrome, also known as IBS, is the most common functional gastrointestinal disorder [9]. The “syndrome” label means that we don’t know what exactly causes it, but there are many usual suspects.

The symptoms of IBS typically include abdominal pain or discomfort associated with changes in bowel habits [9].

There are three main subtypes of IBS [9]:

  • IBS-C: constipation-predominant
  • IBS-D: diarrhea-predominant
  • IBS-M: mixed (characteristics of both constipation and diarrhea, or alternating constipation/diarrhea)
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Potential causes of IBS include factors that disrupt the gut-brain connection and create symptoms [2]. Those factors may be:

  • Genetic: Researchers have long known that there are genetic risk factors in the development of IBS, but so far, a specific IBS gene has not been identified [10].
  • Environmental: exposure to chemicals, toxins, poor air quality, lack of sun exposure, etc.
  • Psychological: early childhood trauma, chronic stress, anxiety, etc.

Disruptions to the gut-brain connection can cause [2]:

  • Gut motility changes (speeding up or slowing down digestion, causing diarrhea or constipation) 
  • Visceral hypersensitivity (a highly sensitive gut) 
  • Leaky gut (where food particles and toxins may pass into the bloodstream through the gut lining when they are not supposed to)
  • Immune system activation (especially because at least 70% of the immune system lives in the gut)
  • Gut microbiome dysbiosis (imbalance in gut bacteria)

Any of these changes can produce the uncomfortable and often painful symptoms of IBS [2].

Figuring out what is behind IBS is a highly individual and personalized quest, and learning the personal triggers behind your IBS symptoms will reveal the path to recovery.

Does Having a Family Member with IBS Increase Your Likelihood of Having IBS?

Senior man talking with his adult sons in garden

Yes, your risk of IBS is increased by having a family member with IBS, but the risk increase is not due to genetics alone.

Epidemiological research (the study of public health concerns in a population) has shown that first-, second-, and third-degree relatives of IBS patients have a significantly greater risk of developing IBS than relatives of people without IBS [3].

Other observational research has found that both male and female relatives of IBS patients are 2-3 times more likely to develop the disorder [4]. Not only that, but the more prevalent IBS is in your family, the more likely your IBS symptoms are to be worse than average [4].

Even close non-blood relatives, such as spouses, of IBS patients have a higher than usual risk of IBS [3]. This finding suggests that simply sharing the same environment (with similar social, stress, emotional, and eating patterns) with an IBS patient increases your risk.  

As one literature review summarized,

IBS is a complex, stress-related disorder that may be passed down in families as a result of genetics or shared environmental factors.”

In this statement, we can identify three possible factors leading to increased risk of IBS among family members: stress, genetics, and environmental factors. 

Theoretically, a combination of chronic stress and environmental factors may lead to the development of IBS in two related family members, such as a parent and child or siblings. Genetics may or may not be part of the equation. 

Furthermore, research has reported only weak genetic associations with IBS; there is not enough evidence to suggest that major genetic factors play a role in its development, with the notable exception of sex. In general, females are more likely to develop IBS than males [11].

All of this is to say that there is no IBS gene dooming you to have IBS, or to pass it on to your children. IBS is much more complex than a single genetic root cause and as such, there are many ways to prevent and treat it.

Are There Specific Genes Found in IBS Patients? 

Several genetic polymorphisms (also called SNPs) have been associated with IBS. The most studied genetic variants that may affect the development of IBS are polymorphisms of the serotonin transporter (SERT) gene [12].

An important note before we continue: this is interesting data to know if you have access to genetic testing, but there is no need to stress over whether you have specific SNPs. Most IBS treatment options, especially the foundations of health like diet and movement, will be similar regardless of these genetic variations.

According to several genetic studies, including a recent systematic review and meta-analysis, researchers have found that the following genes have single nucleotide polymorphisms (SNPs aka genetic variants) that likely play some role in IBS [2]:

  • Serotonin transporter protein (SERT gene) [2]: Additionally, a SERT polymorphism may be a genetic identifier of IBS in Caucasians [13], but it is especially associated with IBS-C in Asians [12]. It may also generally increase the risk of IBS and contribute to pain severity [7].
  • Catechol-o-methyltransferase (COMT gene) [2]: COMT polymorphisms may also affect pain severity and sleep disturbance in IBS [7].
  • Beta 3 subunit of G-protein (GNB3 gene) [2]: However, some studies have found no associations between the G-protein beta polypeptide 3 (GNB3) polymorphism and IBS risk [14].
  • Voltage-gated mechanosensitive sodium channel NaV1.5 (SCN5A gene) [2, 10]
  • Tumor necrosis factor-alpha (TNFSF15 gene) [2, 15]: One of the two implicated TNFSF15 polymorphisms may also contribute to pain severity and sleep disturbance [7].
  • IL-10 gene: One IL-10 SNP may increase IBS risk in Caucasians, and another IL-10 SNP may do the same in Asians [5]. A different SNP of IL-10 was associated with a lower risk of IBS [2].
  • NF-kappa B (NF-κB gene): Mind-body treatments may help NF-κB regulate the immune system and help counteract the negative effects of stress in IBS and IBD [6].
  • Oxytocin receptor (OXTR gene): One OXTR SNP may increase the risk of IBS [7].
  • Adrenoceptor alpha 1D (ADRA1D gene): One ADRA1D polymorphism may increase the risk of fatigue in both IBS patients and healthy controls [7].

Another interesting finding is that some gene locations (loci) associated with IBS may also be associated with mood and anxiety disorders [8].

Ways to Counteract a Genetic Predisposition to IBS

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Most people’s first thought when looking into the causes of IBS isn’t going to be genetic testing. Fortunately, the strategy for counterbalancing a genetic susceptibility to IBS is going to be much the same whether you have access to testing or not: a healthy diet, stress prevention and management, and keeping a balanced microbiome.

Prioritize Stress Relief

Chronic stress especially is a much bigger factor in IBS than we tend to think, and research supports this.

A clinical trial of 19 IBS patients and 29 IBD patients found that a 9-week relaxation response-based mind-body group intervention led to the following:

  • Improved pain catastrophizing, anxiety, and quality of life in IBS and IBD (Crohn’s disease and ulcerative colitis)
  • Reduced symptom severity in IBS
  • Altered gene expression of 1,059 genes in IBD (related to inflammatory response, cell growth and proliferation, and oxidative stress pathways) and 119 genes in IBS (related to cell cycle regulation and DNA damage)

“This is pretty amazing – just teaching people how to calm the stress response and connect the mind and body through meditation, yoga, breath awareness, and other techniques can go so far as to change gene expression, lower inflammation, and improve IBS symptoms.”

Modify Your Diet

Diet is another important factor that may also modify genetic expression, impacting the inflammatory response, digestion, immunity, and other pathways [16].

For example, one study found that consuming blueberries (as a freeze-dried blueberry supplement) initiated significant changes in the expression of 49 genes [17].

Ginger powder was shown to significantly affect gene expression in rheumatoid arthritis patients, initiating changes in inflammation and immunity [18].

This isn’t to say that you should or shouldn’t eat these foods, but that food has the power to change your gene expression positively or negatively. Prioritizing a diet that avoids trigger foods and focuses on whole food nutrition is essential for a healthy gut [19, 20].

One example is the low FODMAP diet, which removes high FODMAP foods (certain complex natural starches and sugars that may be difficult to digest) and prioritizes easier to digest low FODMAP foods. This diet has multiple studies backing it for IBS symptom relief and still provides plenty of nutrients and satisfying meal options [21, 22, 23, 24]. To learn more, you can get our low FODMAP diet guide here.

Shift Your Microbiome

The state of the gut microbiota can also influence what genes are expressed or not expressed, as well as influence digestion and mental health (since some gut bacteria are responsible for producing neurotransmitters like serotonin and dopamine) [25].

Certain bacteria, fungi, and other microbes that do not belong in the gut may also trigger IBS symptoms [26]. This was the case for Mona, who came to our clinic with acid reflux and IBS. 

Mona’s symptoms were chronic reflux, excessive saliva, bad taste in the mouth, coughing, bloating, stomach growling, and constipation. Through a combination of a low FODMAP diet, antimicrobials, and probiotics, she was able to regain her gut health and is now symptom free. 

Taking a full spectrum of probiotics is part of our foundational approach to IBS treatment at the Ruscio Institute. In my clinical experience, patients will see positive changes in their gut health when taking a combination of multi-species, soil-based, and S. boulardii probiotics. If you have tried just one of these probiotics before without seeing any changes, triple probiotic therapy (along with a healthy diet) is a good next step. 

Rebalancing the microbiome does not have to be difficult, but it may require some experimentation. If you want the guidance of doctors who specialize in gut health, reach out to us at the Ruscio Institute for Functional Medicine

Genetics Aren’t the Only Factor in IBS

In fact, genetics likely play a much smaller role in IBS cases compared to environmental factors, diet, and psychological stress. Regardless of your IBS genotype (any genes you may have that predispose you to IBS), it’s much more important to know how IBS physically presents for you, your IBS phenotype.

Healing IBS takes a multipronged approach, taking diet, environment, mental/emotional state, and the microbiome into account. You can learn more about healing the gut in my book Healthy Gut, Healthy You or visit us at the Ruscio Institute for Functional Medicine to speak with a gut health doctor.

➕ References
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