The Effect of Gut Bacteria on Mood

By Jonathan Hunsaker

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You may have heard lots of talk recently about the importance of having a “healthy gut.” This is an emerging area of research and scientists are continuing to discover precise reasons why the gut (aka gastrointestinal system or GI tract) is one of the most important biological systems in the human body.

[Note: Terminology can vary when talking about gut health. For instance, intestinal flora (or gut bacteria) is often referred to as “microbiota,” and the biological system comprising these trillions of organisms is called your “microbiome.” In other words, you have trillions of microbiota in your microbiome, which reside in your GI tract, or gut. Another common term used to describe the beneficial / good gut bacteria is “Probiotics.”]

Here are just a few of the important discoveries researchers have made about the gut:

  • The majority of nutrient and water absorption takes place in the gut.
  • Around 20 hormone processes are connected to or have processes in the gut.
  • The GI tract contains more than 1 billion nerve endings and has more surface area than that of your external skin. These neurotransmitters, known as the enteric nervous system (ENS) are so involved in your body’s processes, scientists have nicknamed the gut the “second brain.”water and nutrient absorption takes place in the gut
  • There are over 100 million neurons in the ENS; more than the spinal cord, or the peripheral (outside of the brain or spinal cord) nervous system.
  • The brain doesn’t need to operate the GI system. The second brain can act independently. In some cases the ENS sends signals to the brain, not the other way round [1].
  • The “gut-brain axis” describes the influence the gut, microbiome, and ENS have on the brain, including both emotional and cognitive functions [2].
  • The gut contains 70% to 80% of your body’s immune cells.
  • The GI microbiome prevents colonisation by potentially pathogenic (“bad”) microorganisms, provides energy for the gut wall from undigested food, and it regulates the mucosal immune system [3].
  • GI microbiota contribute to energy homeostasis (stability), prevent mucosal infections and, importantly, contributes to the maintenance of an intact GI barrier, which seems to be closely related to infectious, inflammatory, and allergic diseases [4].
  • Any disruption to the harmony of the GI microbiome affects the function of the host’s (your body’s) defense systems.

Can Your Gut Health Impact Your Mood?

Probably the most surprising effect the Gut-Brain Axis and microbiome have on your body is that to do with mood [5].

Science has long-recognized much of our supply of neurochemicals originate in the intestines. Most of your serotonin is made there [6], as well as approximately 50% of dopamine.

However, it’s only recently that serious consideration has been given to the role our microbiota (the bacteria in the gut) play in creating those chemicals [7,8].

A 2015 story in The New York Times shares interviews and quotes with several scientists on the cutting edge of this area of research, including one of the first to propose the neurochemical aspects of the gut-brain axis − Mark Lyte, a microbiologist at the Texas Tech University Health Sciences Center [9].

Lyte and other researchers have found that among the many chemicals secreted by our microbiota, some are identical to the substances “used by our neurons to communicate and regulate mood, like dopamine, serotonin, and gamma-aminobutyric acid (GABA).

These, in turn, appear to play a function in intestinal disorders, which coincide with high levels of major depression and anxiety [10].”
research into the connection between gut bacteria and mood

For example, in 2014 a group of Norwegians studied the feces of 55 people, noting depressive patients had certain bacteria in common.

It’s due to this type of research that it’s becoming more commonly accepted that anxiety, depression, and several pediatric disorders, including autism and hyperactivity, are linked to gastrointestinal abnormalities [11].

It was once thought that stress caused the immune system to be weakened, which in turn affected how bacteria in our microbiome behaved. Now, somewhat revolutionarily, research indicates that certain bacteria actually cause stress, which then impairs the immune system.

The truly exciting aspect of all this science is work that Lyte and his peers are doing in the realm of reversing disorders. For instance, using the secretions of certain bacteria to relieve anxiety and elevate mood by putting the microbiome back into harmony—proposing probiotics (beneficial, life-giving organisms) can be tailored to treat psychological disorders. These are somewhat flippantly being referred to as “psychobiotics [12].”

One exciting study carried out in Sweden found that mice raised without microbes were far more active outside. Not only that, the microbe-free mice were observed to have less anxiety and be more daring overall.

Serotonin is a known factor in mood, anxiety and depression, to name a few of its functions [13,14]. The connection to the manufacturing and body’s use of this essential chemical (some consider it a hormone) is gaining increasing attention. Or, as a 2015 publication in Behavioral Brain Research stated [15]:

“The brain-gut axis is a bidirectional communication system between the central nervous system and the gastrointestinal tract. Serotonin functions as a key neurotransmitter at both terminals of this network. Accumulating evidence points to a critical role for the gut microbiome in regulating normal functioning of this axis … There is also substantial overlap between behaviors influenced by the gut microbiota and those which rely on intact serotonergic neurotransmission.”

More research is being done to identify the precise processes occurring, but it’s certainly becoming crystal clear… the health of your microbiome is essential for even your mental and emotional wellbeing [16].

One way to help support your gut health is with a quality probiotic supplement such as Organixx ProBiotixx+.

Organixx ProBiotixx+ formula contains a single, super-strain of Lactobacillus plantarum, designed to help alleviate constipation… eliminate gas and belly bloat… support your entire immune system… and give you total digestive protection.

Organixx ProBiotixx probiotic formula

Article Summary

  • The GI tract contains more than 1 billion nerve endings and has been nicknamed the “second brain.”

  • The “gut-brain axis” describes the influence the gut, microbiome, and enteric nervous system have on the brain, including both emotional and cognitive functions.

  • Anxiety, depression, and several pediatric disorders, including autism and hyperactivity, are linked to gastrointestinal abnormalities.

  • Secretions of certain bacteria can relieve anxiety and elevate mood by putting the microbiome back into harmony.


    • I am involved with a small fertiliser company in NZ. I do some research and write a monthly column, generally about how fertiliser impacts on the environment, but also articles similar to this one. Is it any wonder that our gut affects our mood?

      The link between soil and human gut microbes

      There is no doubt that human gut microbes play a major role in determining the health of their host. Hippocrates (460-370 BC) stated “All diseases begin in the gut”. A very small sample out of a huge list of these diseases is colic, bloating, flatulence, vomiting, diarrhoea, dyslexia, asthma, allergies, autism, eczema, constipation, depression, arthritis, ADHD, schizophrenia, heart disease, tooth decay, cancer and bowel diseases. The father of modern psychiatry French psychiatrist Phillipe Pinel (1745–1828) correctly stated in 1807. “The primary seat of insanity generally is in the region of the stomach and intestines.” In a healthy adult, there are 1.5-2.0 kgs of microbes jostling for order. Exactly what order they achieve, and the degree of host comfort or discomfort depends partly on our individual diet, and unfortunately partly on food growers’ and processors’ actions. We rely on up to 100 trillion microbes. A well-functioning gut holds the key to our health. Just as a tree with sick roots will not thrive, nor will our bodies or minds thrive without a well-functioning digestive system. Livestock are no different.

      Soil microbes influence the health and defence mechanisms of plants. Guts and roots have large surface areas, with microvilli and folds or root hairs in some parts. Both roots and guts are structured, non-homogenous habitats with pH, nutrient, water, and oxygen differential levels or gradients. Gradients favour colonization by distinct bacteria that are more successful in some root or gut regions. The more diverse and balanced the gut and root zones are, the better health the hosts will enjoy. Bacillus subtilis, also known as the soil bacteria was first used in the 1940’s to protect troops from dysentery and typhoid. It is resistant to stomach acid and most antibiotics. It has strong immune-stimulating properties and is particularly effective with allergies and autoimmune disorders. Its enzymes are anti-fungal, anti-viral and anti-bacterial. It is not a resident of humans, but is transitional, doing a lot of good as it passes through. It is also the microbe that can clean up the effluent pond. Probiotics containing Bacillus subtilis are the most effective you can get.

      Dr Linus Pauling (1901-1994), winner of two Nobel Prizes, stated: "In my opinion, one can trace every sickness, every disease and every ailment to mineral deficiency." It is logical then, that plant and stock health problems and ensuing chemical intervention are caused by poor fertiliser practices. Fruit and vegetables that do not store lack fertiliser integrity; run-out pastures; effluent pond problems and failures are directly related to incomplete or poor fertiliser practices. In recent times there have been outbreaks of pests and diseases; porina, army worm, Psa, aphids, facial eczema and toxic swedes to name a few. These are symptoms that the soil microbes and plant roots are not being fed a balanced diet. When the soil is balanced properly, these problems do not happen unless chemicals or GM are involved. The problems are, in fact, self-inflicted. Fertilisers and food can stimulate microbes, so why are the wrong microbes being stimulated in the majority of cases?

      Glyphosate, an antibiotic is used to prepare feed for animals and humans. The plants and animals or their products end up as human food. Among many other negatives, glyphosate reduces manganese in the rhizosphere by disrupting microbes. Lactobacillus levels are low in the human gut in association with autism; this creates a vacuum that allows pathogens to overgrow causing ill-health. Lactobacilli normally have high intracellular levels of manganese which enables them to control toxic oxygen bacterial species. It has been found that autistic children have 60% less manganese than they need. Similarly, reproductive capacity of animals is reduced as uteruses atrophy through lack of manganese. Sperm count is also reduced.

      Glyphosate has decreased brain levels of vitamin B12 in elderly, autistic and schizophrenic people. Subjects with both autism and schizophrenia have three-fold lower levels of vitamin B12 in the brain. B12 deficiency also causes dementia. Nutrition of Lucerne through one glyphosate spray the previous season, has reduced boron 18%, calcium 17%, copper 20%, iron 49%, magnesium 26%, manganese 31%, nitrogen 13%, phosphorus 15%, potassium 46%, sulphur 52% and zinc 18%. Those people suffering any of the diseases listed above are similarly affected, as their gut microbiome is unable to properly process minerals. Imagine how much more productive everything would be with correct fertilising and fewer chemicals.

    • It implies that probiotics could have a place in the longterm treatment modalities. However, since it is an "emerging" area of research, we likely won't know the full impact for decades to come. Very exciting stuff!

      • It's only "emerging" here in the USA. Other countries have been consuming probiotic foods for thousands of years and already know about their health benefits. Glad we've finally recognized it. :)

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