The human body is home to more than 100 trillion microorganisms, including bacteria, fungi, protozoa, and viruses. They inhabit nearly every part of the body from the surface of the skin to the lining of the intestines.1,2 

These trillions of partners are vital to maintaining health in many ways. Here are some interesting facts about the microorganisms that inhabit your body – your gut in particular.

Microbiome Vs Microbiota

Although they are often used interchangeably, the terms microbiome and microbiota are different.1,2

  1. Microbiota refers to microorganisms – bacteria, fungi, protozoa, and viruses – that live on and inside humans, other animals, plants, and other organisms.
  2. Microbiome refers to the collection of all the microorganisms and their genes.
  3. Your microbiome has its own set of genes. Because you and your microbiome have a different genetic profile, this means you are carrying around two sets of genomes – yours and your microbiome's.

Different Body Regions Have Different Microbiomes

Microbiomes are unique, like a fingerprint, and different for everyone – including family members and even identical twins.1-3  

  1. The skin, lungs, mouth, vagina, uterus, penis, eyes, urinary tract, gastrointestinal (GI) tract, and other parts of your body have distinctly different microbiomes composed of unique microbiota.
  2. The separate microbiomes combine to make a unique microbiome for each person.
  3. Unlike human genes, the microbiome is dynamic; it changes in response to external and internal factors.

The Gut Microbiome

The largest population of microorganisms in the human body lives in the GI tract.1,2,4

  1. The mouth, esophagus, stomach, and intestines form the GI tract. 
  2. Bacteria and other organisms living in the GI tract are called the gut microbiota. 
  3. Most of the microbes in your GI tract live in your large intestine.
  4. Approximately 500-1,000 different species of bacteria inhabit the GI tract. 

Microorganisms in the gut help maintain health in many ways, including:4-6 

  1. Building and regulating your immune system
  2. Protecting your GI tract from harmful bacteria and viruses  
  3. Digesting food and extracting nutrients
  4. Producing vitamins your body can't make on its own
  5. Communicating with your brain and regulating the stress response
  6. Producing health-promoting short-chain fatty acids

The Gut Microbiome Changes Throughout Your Lifetime

Although relatively stable over time, the microbes in your GI tract are constantly adapting to internal and external factors.7-9

  1. Infants get their first dose of bacteria and other microbes from their mothers during birth and then from their newborn diet. 
  2. Gut microorganisms rapidly increase in variety of species and total number when a baby begins eating solid foods. 
  3. During late childhood, the gut microbiota stabilizes and begins to resemble that of an adult.
  4. Aging is associated with a decline in the variety and number of gut microorganisms.

Your Living Environment Determines the Microbes in Your Gut 

Your environment – including who you live with – has more of an impact on the microbes in your GI tract than your genetics.9,10

  1. People who live together more than likely eat the same foods, share similar lifestyle habits, and are exposed to the same environmental microbes, which all impact the gut microbiome.
  2. One study found that the gut microbiomes of unrelated people who live together are more similar than microbiomes of related individuals who live apart.11
  3. The study also compared the microbiomes of individuals who are related, but don't live together, and found their microbiomes share no more similarities than those of a stranger's microbiome.11  

Your Diet Has a Large Influence on the Gut Microbiome

The foods you eat greatly affect gut microbial content. This impacts your overall health – for better or worse.6,9,12  

  1. Eating a wide variety of foods is associated with having a higher variety of gut microbes, which is associated with a healthier microbiota.13,14
  2. Young people trying out a wide variety of foods have more diverse gut microbiota than adults who follow a distinct dietary pattern.14
  3. A typical Western diet (low in fiber, high in animal protein and fat) is associated with a decreased variety of bacteria in the gut and a reduction in beneficial bacteria.14  
  4. A significant dietary change, such as switching to a strictly animal-based or plant-based diet, can alter microbial composition within 24 hours.14  
  5. Foods like fruits, vegetables, whole grains, and beans contain fiber – which serve as food for the bacteria living in the gut.15
  6. Fermented foods like yogurt, sauerkraut, and kimchi contain beneficial bacteria that support the gut microbiota.16

Antibiotics Profoundly Alter Gut Microbes

Antibiotics have a profound effect on gut microbes.

  1. A single dose of a broad-spectrum antibiotic can decrease the variety of gut bacteria for many weeks.6
  2. Avoid unnecessary antibiotics. When a medication is necessary, a narrow-spectrum antibiotic should be used for the shortest duration possible.6

Exercise is Good for the Gut Microbes

Exercise has a host of benefits for the mind and body. Getting your heart rate up might also have a positive effect on your gut microbiome.

  1. Studies indicate that aerobic exercise increases the abundance of beneficial bacteria and overall variety of microbes in the GI tract.17,18 
  2. One study found that women who engaged in at least three hours of light exercise per week – such as a brisk walk or swimming – had increased levels of beneficial bacteria in the GI tract compared to the GI tracts of sedentary women.19

A healthy gut microbiota is essential to living a healthy life. As the scientific world expands its knowledge about the microorganisms that compose the gut, new insights will lead to new approaches of treating disease and improving health and wellbeing. 

A Word from Thorne

How diverse are the microbes in your gut? You can explore your own gut health in the privacy of your home with Thorne’s Gut Health Test. This gut microbiome test will give you a detailed analysis and a personalized plan to optimizes wellness. The test combines cutting-edge sequencing with Onegevity’s Health Intelligence platform to make meaningful changes.


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  3. The human microbiome project. National Institutes of Health. [Accessed Nov. 10, 2021.]
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