What Is The Gut Microbiome?

What Is The Gut Microbiome?

Introduction: What is the Gut Microbiome?

The gut microbiome is a complex ecosystem of bacteria, viruses, some fungi, and parasites unique to each person. Infants first inherit their microbiome from their mother during birth and breastfeeding, and in later life, diet and environment continue to introduce new microbes. There are bacteria all through our GI tract, but most live in our large intestines where oxygen levels are lower and away from the strong pH of stomach acid.

These microorganisms have a symbiotic relationship with their hosts, humans, which means we both benefit from each other. Humans provide shelter and food for the microbes, and in return, they provide essential services like helping digestion and aiding our immune systems. Gut dysbiosis (imbalances in the gut microbiome) can affect everything from digestion, weight gain, allergies, heart health, and even cancer risk. Keep reading to find out how your gut microbiome helps your body function and what you can do to keep it healthy.

Digestive Health

The primary role of the gut microbiome is to aid in digesting foods and nutrients that we wouldn’t be able to process through just stomach acids. These bacteria can break down certain dietary fibers and complex carbs into forms that our bodies can use. They produce ‘short chain fatty acids’ (SCFA) as byproducts, which feed the cells lining the gut and help keep the intestine barrier healthy, as well as producing enzymes that help to synthesize vitamins like B1, B9, B12, and K.

Another way your gut microbiome aids in digestion is through metabolizing bile. Your liver sends bile to your GI tract to digest fats. Afterward, the bacteria in your gut and their enzymes help to break it down so those bile acids can be reabsorbed and recycled. If they didn’t do this, your liver wouldn’t be able to make enough new bile to digest and absorb fats, and the leftover cholesterol would build up in your blood.

Immune System Regulation

Your gut is the largest immune system organ. It contains up to 80% of your body's immune cells. Microbes in the gut also help to train your immune system to tell the difference between beneficial bacteria and pathogenic (disease-causing) types. They also directly compete with unhelpful bacteria for real estate and nutrients, which helps to prevent harmful bacteria from overgrowing. Some chronic GI bacterial infections, like C. difficile and H. pylori, are related to diminished gut microbiomes.

The ‘short chain fatty acids’ (SFCAs) that your gut bacteria produce aid your immune system by maintaining the gut barrier, keeping bacteria and other toxins from escaping into your bloodstream. SFCAs can also have anti-inflammatory properties. Inflammation is a normal function of your immune system, but chronic inflammation is a feature of some autoimmune diseases and can have a role in things like cancer. SCFAs can help suppress these types of inflammation. Developing a healthy gut microbiome can alleviate symptoms of chronic gut diseases like ulcerative colitis and Crohn’s disease.

Gut-Brain Axis

Your gut communicates with your brain through a collection of nerves, neurons, and neurotransmitters that run throughout your GI tract. This connection goes both ways, allowing your brain to influence your GI activities and your gut and microbiome to influence your mood and mental health. Certain bacteria in your gut produce or stimulate the production of neurotransmitters like serotonin. Research has shown that changes in the gut microbiome are linked to changes in the emotional and cognitive centers of your brain, and GI disruptions have been associated with several mood disorders like depression and anxiety. The SFCAs that bacteria produce also have a positive effect on your central nervous system by regulating inflammation, reducing oxidative stress, and maintaining the integrity of your blood-brain barrier.

Weight and Metabolism

Your gut microbiome interacts with your endocrine system and plays a significant role in metabolism. Microbes and their products secrete hormones that regulate your metabolism, like blood sugar and hunger. They also influence how fats are absorbed in your GI tract, which can affect how fat is stored in the body. Fluctuations in the diversity of gut microbes can contribute to weight gain and might be involved in metabolic syndrome.

(There is a study of infants regarding the relationship between gut diversity and diabetes onset that I can include if you want.)

What Factors Affect Your Gut Microbiome?

• Diet: The microbes in your gut thrive on various plant fibers, and different microbes prefer different whole foods. Foods high in sugar and saturated fats tend to favor less beneficial bacteria, which can cause imbalances. Processed foods lack fiber and other micronutrients. They also can contain additives like preservatives and aspartame that harm the good bacteria.

• Infections: Invasive pathogens can cause gut infections that can be temporary or become chronic. These infections cause diarrhea, inflammation, and damage to the gut lining.

• Chemicals: Environmental toxins like tobacco smoke, alcohol, and pollutants can poison and diminish the microbiome. Medications like acid blockers can lower the pH of the GI tract, making it harder for good bacteria to grow. Antibiotics can wipe out good bacteria as well as harmful, causing imbalances if taken for longer than necessary.

• Diversity: A healthy gut microbiome has a diverse ecosystem of bacteria that each perform specific services and support each other. Some bacteria feed different types, and their byproducts affect the gut environment. If the microbiome isn’t diverse enough, it becomes more vulnerable to being overgrown by invasive bacteria due to less competition.

• Motility: Motility refers to the regularity of your bowels. The regular movement of your bowels is how your ‘crop’ of bacteria turns over and gets distributed through the GI tract. How long this takes can affect the population of gut bacteria. If it moves too quickly, the bacteria don’t have time to colonize and do their jobs before being cleared. However, if it moves too slowly, they can overeat and overgrow.  

• Symptoms of an Unhealthy Gut: An imbalance or disruption of your gut microbiome can cause a variety of symptoms, like

• Poor digestion
• Gas/Bloating
• Lower abdominal pain
• Diarrhea
• Constipation
• Fatigue
• Weight gain
• Skin conditions like acne and psoriasis

How Can You Promote Gut Health?

• Increase Fiber: Foods that are high in fiber are called prebiotics. They promote increased levels of SCFAs and help reduce inflammation. These include raw forms of garlic, bananas, seaweed, leeks, asparagus, dandelion greens, and artichokes. A diverse diet with whole grains, fruits, and vegetables can provide suitable dietary fibers to encourage the growth of good bacteria.
• Fermented Foods: Foods like yogurt, kombucha, kimchi, miso, and sauerkraut contain live organisms and can help ‘re-seed’ good bacteria. You can also take probiotics in supplement form.
• Exercise: Some studies have shown a connection between exercise and gut health. Adding an exercise regimen to your routine can help keep your microbiome healthy.
• Limit Alcohol and Artificial Sweeteners: Alcohol can disrupt the good bacteria in your gut and cause imbalances, especially in large amounts. Artificial sweeteners like aspartame can increase blood sugar by stimulating the growth of harmful bacteria.  
• Only take antibiotics when necessary: The overuse of antibiotics can reduce the diversity of bacteria in your gut, cause changes in metabolic activity, and cause the harmful bacteria to grow stronger.

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