How Lack of Stomach Bacteria, Bacteroides, May Trigger Depression

Science continues to unveil the undeniable gut brain connection as microbiome testing continues to grow in the world of conventional medicine. While we are aware that the vagus nerve was a spy sent from the brain down to the gut biome, many are unaware which intestinal flora (or lack thereof) may be triggering an adverse reaction from the vagus nerve. Now, research suggests decreased levels of Bacteroides may be the reason millions of people experience bouts of depression.

Welcome to the Gut Biome

Our body is home to trillions of microorganisms that influence everything from the digestion of food to weight distribution to mental health.

Many outlying factors impact the microbes that comprise our gut biome. From our dietary choices to stress to exposure to toxins, beneficial bacteria that have been with us since day one take a beating.

When we are young, the system is resilient enough to recover from these constant onslaughts. However, the system is only as strong as its weakest link. That means it’s only as strong as the decisions we make.

Over time, our beneficial stomach bacteria gives way to inflammation, viral infection, and mold toxicities. In its wake, harmful bacteria begin to fester. As these opportunistic pathogens continue their duplication, they overthrow the beneficial bacteria within the system.

Lack of Microbe Diversity and Mental Health

A lack of biodiversity in the system can be hazardous to our mental health. In fact, research suggests that a common thread among children with autism is a lack of microbial diversity in their gut biome 1.

One of the stomach bacteria the analysis focused on was Bacteroides. While researchers were unaware then, we now know that Bacteroides play a much more significant role in mental health than we realized.

What Are Bacteroides?

Like many of the stomach bacteria in our body, Bacteroides live mostly harmoniously with other intestinal flora. They are a genus of gram-negative bacterium that relies on glycan (sugar or polysaccharides) from plants in order to thrive. They are one of the most predominant intestinal flora in the gut biome, comprising up to 25% of the GI tract.

There are many benefits of Bacteroides residing in your gut biome 2. Research indicates these bacterium influence:

  • Nutrient Absorption
  • Expelling Toxins
  • Controlling the Growth of Other Pathogens
  • As you can see, these are pretty essential functions. However, there is more to Bacteroides than regulating the GI tract. They also play a crucial role in mental health. Let’s take a look at a recent analysis that brought this key part of the gut brain connection to light.

    Stomach Bacteria and the Gut Brain Connection

    Scientists at Northeastern University wanted to look further into the gut-brain-axis. They started their study acknowledging the trillion cells in our system and their various responsibilities in keeping the ship known as our body afloat.

    Former NU student, now Scientist Philip Strandwitz, spoke on the importance of microbiome testing and its correlation to mental wellness, stating:

    “In the past 10 years there has been significant work that has linked the microbiome to various components of human health and disease. But the general concept of delivering bacteria or manipulating gut bacteria to improve brain health is still new 3.”

    Philip Strandwitz

    Dr. Strandwitz and team partnered with Weill Cornell Medical College. Researches at Weill Cornell Medical College were already researching depression. The Northeastern University team used a lot of the data and test subjects being analyzed to find some very interesting breakthroughs concerning the gut brain connection.

    Microbiome Testing and Mental Health

    Weill Cornell Medical College turned over brain scans of people who were diagnosed with depression. Fecal samples associated to these brain scans were taken in for microbiome testing.

    This practice was done to see which common stomach bacteria resided in the fecal samples of people with depression. Perhaps more importantly, the microbiome testing also determined which beneficial intestinal flora is in low quantities throughout the gut biome.

    Bacteroides in Microbiome Testing Samples

    With Bacteroides comprising at least 25% of our gut biome, it’d be pretty striking to omit this bacterium from an average fecal sample. Yet, the analysis of the fecal samples provided by Weill Cornell Medical College found very little traces of Bacteroides strains.

    Low levels of Bacteroides caused a red flag to raise for

    Dr. Strandwitz and crew. They started going through other analyses on this stomach bacteria and saw a clear connection between a lack of Bacteroides and depression.

    Why a Lack of Bacteroides May Cause Depression

    Research suggests that this stomach bacteria plays a monumental role in the production of gamma-aminobutyric acid (GABA) 4. Over one-third of the synapses in your brain uses GABA, making this neurotransmitter essential to many brain functions.

    GABA is known as our inhibitory neurotransmitter. It seeks out overexcited neurons and binds to them. When this happens, GABA exerts a calming effect on the neurons 5.

    When neurons go wild, it’s like letting a baby bull into a trampoline park. It just bounces around, creating damage everywhere it goes. As the excited neurons wreak havoc, your internal system gets upset. Anytime your insides are angry, you will project this sadness on the outside, triggering bouts of depression.

    Cell Communication and Depression

    The reason Bacteroides are so influential is due to how these stomach bacteria communicate through the gut-brain axis. Research shows that the gut lining is rich with enteroendocrine cells.

    Recently, scientists discovered that enteroendocrine cells have foot-like patterns that resemble synapses. Due to their molecular structure, enteroendocrine cells can communicate with neurotransmitters, such as GABA 6.

    As Dr. Strandwitz explained,

    “It’s like a highway of communication from the brain to the gastrointestinal tract. As it turns out, about 80 percent of signaling that happens along the vagus doesn’t go from the brain to the gut. It goes from the gut to the brain 4.”

    Dr. Strandwitz

    While going down the rabbit hole in figuring out the gut brain connection, that is when scientists realized that GABA relies on Bacteroides for maximum production levels.

    Stomach Bacteria Endangering GABA

    GABA is a precious commodity in our system. Not only does it help calm the brain, but it also proves as food for stomach bacteria. While Dr. Strandwitz and Dr. K. Lewis witnessed the Bacteroides and GABA relationship, they realized another shocking discovery, one opportunistic stomach bacteria was on a GABA-only diet.

    There are trillions of microbes, with new ones being discovered everyday. However, none are known to feed off a singular neurotransmitter.

    As Dr. K. Lewis stated,

    “It’s remarkable. I’ve been doing microbiology for a very long time and I have never encountered, and the profession has never encountered, a bacterium that eats one thing and only one thing: GABA 4.”

    Dr. K. Lewis

    Upon witnessing this feast, the scientists named the microorganism Evtepia gabavorou. Loosely, the name translates to GABA-eater.

    Why GABA Relies on Bacteroides

    The discovery of Evtepia gabavorou makes sense as to why a lack of Bacteroides can be catastrophic for GABA production. Without beneficial intestinal flora spurring the growth of GABA, opportunistic stomach bacteria will gobble it up. Without GABA in our system, the noise in our brain is amplified. These might result in feelings of anxiety or depression.

    To keep Bacteroides high, you should try microbiome testing. That way you can figure out which stomach bacteria is causing gastrointestinal distress and which intestinal flora you need to make the gut biome more diverse.

    Microbiome Testing for Bacteroides

    If you think your gut biome is running the risk of being low on this essential stomach bacteria, let Ombre help. With our At-Home Gut Health Test Kit, we send you everything you need to sample your gut biome in the privacy of your house.

    Like Dr. Strandwitz and crew, we use microbiome testing to determine the current state of your intestinal flora. Our Microbiome Testing Kit provides you with a couple of sterile swabs to use for collecting a stool sample from your toilet paper. Swirl the sample on the swab inside of the vile we provide. Your sample will be preserved in the liquid inside the vile.

    Simply mail in the sample by placing it int he discreet addressed envelope we provide. Our specialists analyze your sample and determine which microbes are in your system. From there, we offer food and probiotic recommendations specifically for your gut health.

    Why Test Your Gut?

    Sure, we want more Bacteroides to fight off depression. However, there’s always something to be said about too much of a good thing. Research also shows that Bacteroides can be troublesome for the gut biome when the bacteria overgrow. They can grow into a bit of a bully.

    One analysis noted,

    “Organisms such as Bacteroides with such a large genome bank at their disposal may simply need to turn on certain genes (such as those involving new nutrition pathways, efflux pumps to rid the cell of toxic substrates, or new surface epitopes) to change from friendly commensal to dangerous threat 7.”

    Bacteroides are a strong bunch. When you have a Bacteroides overgrowth, it is very hard to get rid of them. That’s because these opportunistic stomach bacteria have proven to be antibiotic resistant 8. This sort of metamorphosis may become one of the biggest health crises of our future.


    To avoid the overgrowth of Bacteroides, get rid of the guesswork. Instead of taking a generic gut health supplement, we can determine if your system really needs more of this gut bacteria.  

    Feel your best. Test your gut.

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    • 1 Li, Q., Han, Y., Dy, A., & Hagerman, R. J. (2017). The Gut Microbiota and Autism Spectrum Disorders. Frontiers in cellular neuroscience, 11, 120. doi:10.3389/fncel.2017.00120.
    • 2 Wexler H. M. (2007). Bacteroides: the good, the bad, and the nitty-gritty. Clinical microbiology reviews, 20(4), 593–621. doi:10.1128/CMR.00008-07.
    • 3 “These Bacteria May Be the Key to Treating Clinical Depression.” Neuroscience News, 11 Dec. 2018, neurosciencenews.com/bacteria-clinical-depression-10323/?fbclid=IwAR3nr5aQHl9LsdvLQyWzuAbczNpTMxeZ7NBFykzDXqlJT-8d-ILaeAQPups.
    • 4 Strandwitz, Philip, et al. “GABA-Modulating Bacteria of the Human Gut Microbiota.” Nature News, Nature Publishing Group, 10 Dec. 2018, www.nature.com/articles/s41564-018-0307-3.
    • 5 Purves D, Augustine GJ, Fitzpatrick D, et al., editors. Neuroscience. 2nd edition. Sunderland (MA): Sinauer Associates; 2001. GABA and Glycine.Available from: https://www.ncbi.nlm.nih.gov/books/NBK11084/.
    • 6 UnderwoodSep, Emily, et al. “Your Gut Is Directly Connected to Your Brain, by a Newly Discovered Neuron Circuit.” Science, 26 Sept. 2018, www.sciencemag.org/news/2018/09/your-gut-directly-connected-your-brain-newly-discovered-neuron-circuit.
    • 7 Microbiology. The thin line between gut commensal and pathogen.Gilmore MS, Ferretti JJScience. 2003 Mar 28; 299(5615):1999-2002.
    • 8 Salyers, A. A., P. Valentine, and V. Hwa. 1993. Genetics of polysaccharide utilization pathways of colonic Bacteroides species, p. 505-516. In M. Sebald (ed.), Genetics and molecular biology of anaerobic bacteria. Springer-Verlag, New York, NY.

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