Does gut health affect the immune system?


There are tens of trillions of microorganisms living in your gastrointestinal (GI) tract. Some of these microorganisms are good, some are bad, and both are very telling factors in your overall health.

This crowd of bacteria, fungi, and viruses living in your intestine forms your “gut microbiota”, determining your gut health, nutrition status, immune function, and even mood.

The gut microbiota is a crucial part of your overall health because it:

  • Aids digestion
  • Helps in the absorption of nutrients
  • Aids in the synthesis of vitamin K, folic acid, and other nutrients
  • Produces short-chain fatty acids (SCFA) that reduce inflammation and protect gut mucosa
  • Promotes a healthy gut barrier and boosts gut integrity
  • Helps to regulate and control pathogens
  • Aids the detoxification process
  • Regulates and supports immune function
  • Helps to regulate inflammation
It is important to maintain the right ratio of healthy and harmful bacteria in the gut. An imbalance in good and bad bacteria can lead to gut dysbiosis, a precursor of autoimmune disorders, obesity, mood disorders, poor immunity, anxiety, and other health concerns. On a more positive note, a healthy balance can greatly influence your overall health in many ways.

So, how does gut health affect the immune system and the rest of your body? Let us explore this subject.

The link between gut health and immunity


The bacteria populating your intestine play a major role in the quality of your immune system.

How exactly does this work? Your gut microbiota communicates with your brain and central nervous system to regulate many functions such as stress response, immune function, hormone production, digestion, and metabolism.

If you’re wondering when this population of bacteria begins to thrive in your GI tract, it happens right from birth. Many experts believe that this early development of your gut microbiota determines your overall health in following years. Fascinatingly, studies suggest that a baby can inherit their mother’s gut microbes before they are born.

A 2018 study showed that the method of delivery has a strong influence on the development of microbiota and the immune system in babies. [2] For example, vaginally-born babies are exposed to their mother’s bacteria, activating their immune system. However, for babies born via C-section, the handing down of bacteria is altered. [1] It is believed that this could be why C-section babies are often more vulnerable to allergies, asthma, obesity, diabetes, and chronic inflammatory issues later in life.

What’s more, mother’s milk also plays an important role in the process as it provides nutrition but also contains bioactive and immunity-related components that aid in the building of microbiota. Many studies show that breastfed babies have a healthier gut and stronger immunity when compared to those who are fed solely with formula.

As you grow and are exposed to different microbes via food, infection, and environment, your gut bacteria become more diverse. The gut microbiome undergoes many changes in the first two years of life before stabilizing. However, your gut microbiota and, therefore, your immunity can be greatly altered by dietary choices, age, stress, poor sleep, and overuse of drugs and antibiotics.

The question remains, how does your gut bacteria build and bolster your immunity? Experts are still working on finding all the pieces to this puzzle, but it’s clear that your microbiota sends signals via hormones and chemicals to train the immune system.

The immune system’s job is to fight and control pathogens, and to build a tolerance to beneficial organisms. The microbial community in your gut, on the other hand, develops and activates immune cells, namely T cells. The immune system teaches the T cells to tell the difference between foreign pathogens and your body’s own healthy organisms and tissues. It is thought that certain cells in the gut lining are expert in releasing high numbers of antibodies.

Your gut bacteria also help in the production of short-chain fatty acids (SCFAs) such as butyrate, molecules that are formed when gut bacteria ferment non-digestible carbohydrates. SCFAs are a food source for gut bacteria but they also help to regulate immune function. What’s more, SCFAs protect the intestine’s mucosal layer and maintain the gut bacteria, an important step in controlling inflammation, autoimmunity, and food sensitivity. Research has proven that poor production of SCFAs is linked to obesity and type 2 diabetes.

Gut imbalance, leaky gut, and immunity


The gut lining is another key aspect of the relationship between the gut and immunity. The lining of your intestines absorbs nutrients but is very selective about the particles it allows to pass into the bloodstream. A healthy gut lining does not allow toxic waste, bacteria, or undigested food particles to escape. However, when this lining becomes damaged, the once small gateways grow and become larger, allowing unwanted particles to pass into the bloodstream. This is what’s known as “leaky gut”, caused by stress, zinc deficiency, vitamin D deficiency, poor diet, antibiotics, chronic infections, and excessive alcohol usage.

When leaky gut occurs, the immune system bolsters, creating antibodies and triggering inflammatory responses, ultimately leading to chronic inflammation and pain. Leaky gut and the associated responses can also lead to autoimmune disorders, allergies, and food sensitivities. These occur when the immune system responds abnormally, attacking the healthy tissues in the body.

The importance of a well-balanced and diverse microbiota


To maintain well-balanced immune responses, your body requires a diverse gut microbiota made up of many different types and species of bacteria. Interestingly, research has revealed that those with obesity, celiac disease, diabetes, psoriasis, inflammatory bowel disease, arterial stiffness, and rheumatoid arthritis have a less diverse gut microbiota when compared with healthy people.

Even more fascinating, studies have shown that in high-income developed countries, there are certain factors that contribute to poor bacterial composition. For example, overuse of antibiotics and certain dietary habits have caused a lack of bacterial diversity and flexibility, negatively affecting immunity. This may be an answer to why there has been a drastic rise in chronic, autoimmune, and inflammatory disorders in certain parts of the world. [3]

The composition and diversity of your gut microbiota have a strong influence on immunity, but it also greatly affects metabolism, mood, and heart health. Recent research published in the European Heart Journal illuminated a connection between gut bacteria and the stiffening of arteries. This finding suggests that by positively altering your gut microbiota via diet and probiotic supplements, you may be able to reduce the risk of heart disease. [4]

Your microbiota influences the effectiveness of vaccines


New research suggests that gut microbiota diversity and composition determine how your body responds to vaccines. [5] Those who have leaky gut or gut dysbiosis, your immune system is preoccupied with attacking toxins, bacteria, and fungi that have been allowed into the bloodstream.

How to improve your gut health and immune system

1. Carefully assess and adjust your diet

Wondering what to eat for gut health? Good question. Diet is a huge factor in your gut’s overall health and resilience. A diet full of sugar, unhealthy fats, and highly processed foods containing artificial colors, preservatives, and chemicals reduces the number and diversity of good gut bacteria. On the flip side, fresh, whole foods such as fruits and vegetables protect the good bacteria. Whole, fresh foods are also excellent sources of vitamins, minerals, antioxidants, fibre, and digestive enzymes. Fibre is a key factor in gut health as it cleanses the intestines and nourishes healthy bacteria so they can thrive.

2. Incorporate probiotics

Probiotics are living bacteria (the healthy kind!) that restore the composition and diversity of your gut microbiota. Food sources of probiotics are kimchi, natto, yoghurt, kombucha, and sauerkraut as they contain probiotics as well as digestive enzymes crucial for intestinal health.

3. Don’t forget prebiotics

In order for probiotics to thrive and grow in the gut, they need nutrition in the form of prebiotics, carbohydrates the body cannot break down. The friendly bacteria in your gut feed on these undigested carbs, resulting in the formation of short-chain fatty acids (also beneficial for the gut). You can get your dose of prebiotics from foods such as bananas, leeks, asparagus, and onions.

4. Don’t take antibiotics unnecessarily

While necessary at times, antibiotics kill the good bacteria as well as the bad, upsetting the gut microbiota. Make sure you only take antibiotics when you absolutely need them. For example, don’t take them for a cold or flu, as these are caused by viruses which antibiotics are useless against.

5. Reduce systemic inflammation

Systemic inflammation can cause your microbial ecosystem to become unbalanced. When considering how to improve gut health against the effects of inflammation, curcumin and omega-3 fatty acid supplements can help greatly. There are lifestyle changes you can make too heavily reducing inflammation. The key changes to focus on are reducing sugar and refined carbs, quitting smoking, drinking more water, getting more sleep, and managing stress.

6. Keep stress under control

Chronic stress depletes good bacteria, negatively alters your gut composition and leads to inflammation. These factors cause the gut lining to weaken, increasing the risk of leaky gut, nutritional deficiencies, and other diseases. What’s more, prolonged stress alters the way your gut and brain interact, leading to gastrointestinal issues such as IBD, IBS, peptic ulcers, and GERD. [6]

7. Get enough sleep

As you sleep, your body repairs and rejuvenates from the wear and tear of the day, which is why high-quality sleep is crucial for overall health. What’s more, sleep is closely tied to gut and immune health, as your circadian rhythms affect the function and rhythm of your gut microbiota. This relationship is a two-way street. Poor sleep and sleep deprivation negatively affect your gut bacteria by reducing the number and variety of healthy microbes. These types of adjustments are related to weight gain and other metabolic disorders. On the other side of the coin, poor gut health can be a factor in poor sleep. This comes down to the fact that the bacteria in your gut are closely related to the secretion of neurotransmitters and hormones that induce sleep, like melatonin, dopamine, and serotonin.

8. Increase your zinc levels

Zinc is an important nutrient for regulating digestion, gut health, and immunity problems. Research shows that zinc deficiency can trigger leakiness in the tight junctions across the intestinal lining. By boosting your zinc intake, you can improve your gut barrier function and reduce intestinal permeability (also known as leaky gut). People who suffer from Crohn’s disease and Colitis can also greatly benefit from taking a zinc supplement.

9. Get plenty of exercise

Exercise is excellent for good gut health. In fact, a study found that exercise can adapt the composition and function of your gut microbiota, increasing the number of healthy bacteria, and leading to reduced inflammation. The researchers found that these positive changes happened regardless of diet. Instead, physical activity was connected to changes such as the number of microorganisms that produce short-chain fatty acids (like butyrate). [7] What’s more, exercise is great for proper sleep and stress management, both of which are very important factors in gut health and immunity.

10. Get Dirty

No, it’s not a typo! Don’t be afraid to let your kids engage in outdoor activities where they get a bit dirty in the soil and natural environment. This introduces their immune system to all kinds of bacteria and microbial loads so it can grow and strengthen.What’s more, lay off the antibacterial soaps and sanitizers a little, as excessive usage can kill good bacteria. This leads to a weak immune system that has not been “trained” to be resilient against allergies and infections.

References:

  1. Wampach et al. Birth mode is associated with earliest strain-conferred gut microbiome functions and immunostimulatory potential. Nature Communications. 2018
  2. Francino M.P. Birth Mode-Related Differences in Gut Microbiota Colonization and Immune System Development. Nutrition and Metabolism. 2018
  3. Belkaid et al. Role of the Microbiota in Immunity and Inflammation. Cell. 2014
  4. Menni et al. Gut microbial diversity is associated with lower arterial stiffness in women. European Heart Journal. 2018.
  5. Valdez et al. Influence of the microbiota on vaccine effectiveness. Trends in Immunology. 2014.
  6. Konturek et al. Stress and the gut: pathophysiology, clinical consequences, diagnostic approach and treatment options. Journal of Physiology and Pharmacology. 2011.
  7. Allen et al. Exercise Alters Gut Microbiota Composition and Function in Lean and Obese Humans. Medicine & Science in Sports & Exercise. 2017