What is the gut microbiome?
The human gut microbiome, also known as the intestinal microbiome, contains many different types of bacteria that can influence human health.
In fact, the gut microbiome contains over 1,000 different species of bacteria and is the largest microbiome in the human body (Rogers, 2011). These bacteria are part of what is known as gut microbiota.
Gut microbiota also include fungi, viruses, and other living things that are found in your gut.
Keep on reading to learn about how the gut microbiome can affect human health and disease, learn about the gut-brain axis, and how you can maintain a healthy gut microbiome.
Types of gut microbiota and where are they found
About 90% of the microbial populations found in the human gut microbiome belong to the Firmicutes and Bacteroidetes phyla (Magne et al., 2020).
These are located throughout the gut, with their abundance in certain parts of the gut varying across our lifespan. Their abundance also changes due to different external and environmental factors.
Factors that influence the gut microbiome
Many different factors can affect the composition of an individual’s gut microbiome. For this reason, the gut microbiome of two different people can vary widely and can even change across an individual’s life.
Some of the factors that can change the composition of the human gut microbiome include lifestyle, exercise frequency, body mass index (BMI), along with cultural and diet habits.
The gut-brain axis and its importance
Did you know that there is a direct connection between your gut and your brain? This connection is known as the gut-brain axis.
In fact, there are over 500 million neurons (nervous system cells) in the human gut that are connected to the brain (Mayer, 2011)! When it comes to sending signals between your gut and your brain, the main nerve that transmits these signals is the vagus nerve.
The gut and the brain are also connected through chemicals known as neurotransmitters, which we will explain in more depth in the next section of this article.
Gut microbiome and mental health, anxiety and depression
The main way that the gut microbes can affect a person’s mood is through neurotransmitters. Neurotransmitters are chemicals that are produced within your body that can affect many different things, including mood and emotions.
One example is serotonin, which is a neurotransmitter that produces feelings of happiness (Carpenter, 2012). The gut produces a large portion of the serotonin that is found in the human body, making gut microbiome health an important factor in preventing depressed mood.
Additionally, the gut produces the neurotransmitter called GABA (Duranti et al., 2020). This neurotransmitter is inhibitory in nature and can help reduce feelings of fear, anxiety, and panic.
GABA production is yet another reason why maintaining the health of the gut microbiome is so important.
Importance of the gut microbiome and its effect on health
There are many ways that the human gut microbiome correlates with health and disease.
Negative health effects can arise from something called gut dysbiosis, also known as gut microbiota dysbiosis.
Gut dysbiosis is a state of imbalance of healthy and unhealthy microbes in your gut microbiome. This can lead to reduced intestinal microbial metabolism, a process in which intestinal microbiota break down the food that you eat.
It is important to keep your gut microbiota composition in balance so that intestinal microbiota metabolism occurs properly. This balance can be maintained through gut microbiota manipulation, which involves the consumption of probiotics.
An area that can be affected by the health of one’s gut microbiome is heart health. Healthy gut microbiota can promote heart health by promoting more HDL in the blood, which reduces cardiovascular risk.
Conversely, unhealthy gut microbiota can negatively affect heart health by producing a harmful chemical called TMAO (Trimethylene N-oxide), which increases atherosclerosis(plaque build up) thereby increasing risk of heart attack and stroke (Zhu, 2020).
The gut microbiome stimulates the host immune system. Furthermore, a healthy human microbiome has been shown to have a role in controlling blood sugar levels. This could be especially beneficial in maintaining optimal diabetic glucose control in people with diabetes mellitus.
The gut also produces a number of substances that can affect a person’s health. One of these substances is short chain fatty acids (SCFAs). Short chain fatty acids can reduce appetite and help in the formation of the blood-brain barrier.
There are three main types of SCFAs produced in the gut: acetate, butyrate, and propionate. Acetate is mainly produced by Bifidobacteria, Lactobacillus, Akkermansia muciniphila, Prevotella spp., and Ruminococcus spp. Butyrate is mainly produced by Faecalibacterium prausnitzii, Eubacterium rectale, and Roseburia spp.
Lastly, propionate is mainly produced by Bacteroidetes, Firmicutes, and Lachnospiraceae.
Another thing that the gut microbiome can do is transform primary bile acids into secondary bile acids. Typically, bile acids are known for their function in lipid metabolism, but they can also be important for certain signaling pathways within the human body.
Diseases associated with gut microbiome
There are several diseases that may be affected by the health of the human gut microbiome.
These diseases include:
- Diabetes mellitus
- Non-alcoholic fatty liver disease
- Inflammatory bowel diseases
- Colorectal cancer
- Heart disease
Inflammatory bowel diseases (IBD) and irritable bowel syndrome (IBS)
Let’s take a closer look at the interaction between IBD and IBS and the gut microbiome. The human gut microbiome can affect and worsen irritable bowel diseases and irritable bowel syndrome by its role in the regulation of stress. Stress can worsen IBD and IBS, leading to more severe symptoms.
The gut microbiome, as mentioned earlier, can regulate the amount of the neurotransmitters serotonin and GABA (regulate gut hormones and gut flora metabolism) present in the body and therefore affect stress levels.
An example would be that an unhealthy gut microbiome does not produce enough GABA or serotonin, stress levels increase, and therefore the symptoms of inflammatory bowel disease and irritable bowel syndrome worsen.
How can I maintain my gut health and microbiome?
You can maintain your gut health and the gut microbiome in many ways. In the following sections, we’ll explain how both regulation of your diet and taking certain supplements can contribute to a healthy microbiome and gut.
Diets that help the human gut microbiome
Many foods promote a healthy human microbiome, also known as intestinal microbiota in the gut. These foods can help increase good gut bacteria while decreasing bad gut microbiota composition.
- Whole grains
- Fruits and vegetables
- Nuts and seeds
- Dark chocolate
- Green tea
- Red wine
- Apple Cider Vinegar
Supplements that help the gut microbiome
Probiotics are live microorganisms, including bacteria and yeast, that can promote gut health by shaping human gut microbiota populations. They increase the number of healthy gut bacteria present in the intestinal microbiome. Fermented foods are rich in probiotics.
Examples of probiotics are:
- Cheeses containing live or active cultures
- Traditional buttermilk
Prebiotics promote the health of the gut microbiome by acting as a food source for healthy bacteria (Probiotics) within the gut. Healthy microbiota can then increase in number and promote gut health within the human body.
Examples of Prebiotics are:
- Whole grains
Vitamin B12 increases intestinal microbiota’s health by promoting gut bacteria’s growth and life. This will then promote a healthy gut microbiome.
The Human Microbiome Project
The Human Microbiome Project was a research project initiated by the United States Government that sought to better understand the gut microbiome and the gut microbiota that inhabited it.
Human gut microbiota were studied by National Institutes of Health (NIH) researchers for the duration of this research project. Specifically, researchers used genetic sequencing techniques in order to find out more about the gut microbiome.
In order to characterize human gut microbiota, researchers used techniques in metagenomics to understand microbial species and communities in a culture-independent way.
Through this study, researchers discovered many things about human gut microbiota and how they can influence health conditions such as pregnancy and preterm birth, inflammatory bowel disease, and type 2 diabetes.
Fecal microbiota composition
A 3-day stool test can be done to evaluate the fecal microbiota composition. Some of the gut bacteria are associated with Inflammatory bowel disease, IBS, metabolic syndrome, type 2 diabetes, cardiovascular disease, and mood disorders.
Certain species of fecal microbiota- Enterobacteriaceae- were elevated in the very frail experimental group. This may suggest that the type of gut microbes that people house has an impact on frailty, especially in their senior years.
So there seems to be a connection between the gut and the brain. This is through the gut microbiome, which may be the key to happiness.
Recent studies have shown that there is a strong connection between the gut microbiota and mental health. In fact, scientists are now discovering that the gut brain axis (the communication between our brains and guts) is a two-way street; not only does the gut affect mood and anxiety, but mood and anxiety can also affect the composition of the gut microbiota (Appleton, 2018).
Foods rich in probiotics, such as yogurt and sauerkraut, can increase levels of GABA and serotonin, which are both neurotransmitters that affect mood.
There is still much research to be done in this area, but it’s exciting to think about all of the potential applications for improving mental health by considering the microbiota gut brain axis.
We at Bassi Clinic believe in the power of gut health, and its relationship to happiness. Probiotics are the key in improving the over well being of your gut thereby help improve your mood. If you would like to discuss this further with our physician at Bassi Clinic please do not hesitate to call and make an appointment at 602-354-3311.
Appleton, J. (2018, August). The gut-brain axis: Influence of microbiota on Mood and Mental Health. Integrative medicine (Encinitas, Calif.). Retrieved August 16, 2022, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6469458/
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