How do your gut bacteria work with your immune system?
Can you boost your immunity & your overall health by improving your microbiome?
Find out how eating a variety of high fibre foods can boost good bacteria in your gut, to improve your immune system & overall health.
How are our immune system & gut bacteria connected?
Chemicals produced by our gut bacteria from the food we eat, influence our immune system.
Our immune system consists of cells, tissues & organs, working together to defend our body against attacks by “foreign” disease causing microbes (also known as pathogens).
There are many different types of immune cells, all play different parts in your body’s response to harmful microbes that can cause disease.
Scientists are starting to find that our gut bacteria influence how our immune system responds to disease causing microbes.
More immune cells live in our guts (approximately 60%) than in the rest of the human body.
For example, Regulatory T cells (T-Regs) are a type of immune cell which help co-ordinate and calm the immune system
The more Regulatory T cells you have, the less reactive your immune sytem
Our gut bacteria send signals to the T-Reg cells, via the chemicals they produce when they digest fibre in the gut (colon / large intestine).
– calm the T-Regs and control their numbers
– influence the amount of inflammation produced in response to threats
– influence the strength & length of the immune system’s response.
By ensuring our immune system responds calmly to all bacteria, our gut bacteria make sure they are not attacked by our immune system.
It’s a clever way to ensure they survive in the gut.
Our gut bacteria also want to stop invaders setting up home on the gut wall & stealing their hard won food.
They defend their space by:-
– rapidly multiplying to take up space on the gut wall to crowd out invaders (including pathogens)
– releasing chemicals that are poisonous to other bacteria (their own type of antibiotics)
Inflammation & the Immune System
Inflammation is the swelling, redness, and irritation we see & feel when we have an allergy or infection.
It is the immune system’s reaction to injury or potential threats like pathogens.
If the immune system response is too vigorous, too much inflammation can occur, leading to tissue damage & autoimmune responses.
This is a very brief overview of the microbiome & inflammation.
A more diverse mix of gut bacteria leads to a calmer immune system
Research studies increasingly confirm that less diverse gut bacteria can lead to less calm immune systems
The western world has seen a rapid increase in allergies & autoimmune diseases from the 1950s, such as:-
– crohn’s disease & ulcerative colitis
These diseases are all linked by inflammation & overactive immune system responses.
Scientists think the cause of many autoimmune diseases is a less diverse mix of bacteria in the gut.
As microbiomes become less varied, our immune systems seem to get more reactive & twitchy
Research shows that some autoimmune diseases can be linked with a less diverse microbiome.
Studies also show the lower the diversity of microbes in a baby’s guts, the higher the chance of allergies developing later in the child’s life.
20th Century onwards : a less diverse mix of bacteria in the Western Microbiome
Since the 1900s, our lives have become increasingly germ-free, and the diversity of bacteria in the average Western gut is in decline.
Various causes are cited for this change in the microbiome :-
– increasing use of antibiotics
– antibacterial chemicals in cleaning products & hand sanitisers
– change in birth practices with more Caesarians in the West
– less contact with the soil via tending crops / growing food
– reduced microbes in food (with processes like pasteurisation)
Too much hygiene at home and in the wider environment could affect how our children’s immune systems develop, as they come into contact with fewer types of microbes.
We need constant contact with microbes (both helpful & threatening) to educate & maintain a healthy immune system
Since we realised that bacteria cause infections, we have tried to limit the number of bacteria we are exposed to.
We have managed to remove many dangerous infectious diseases thanks to the invention of antibiotics.
But the scattergun action of antibiotics kills both good and bad bacteria in our body.
The result : we lose some beneficial microbes that have been part of our microbiome for generations, evolving with us.
The chemicals they produce, which play a vital role in training & soothing our immune systems are also lost with them.
Boost your gut bacteria : eat more fibre
Studies show the immune system is calmer on high fibre diets
When helpful gut bacteria in the large intestine break down the leftover fibre particles from food, they produce chemicals called short chain fatty acids (SCFAs).
You might have heard of acetate, propionate, and butyrate which are several of the best known & researched short chain fatty acids.
Research has found that these SCFAs send calming signals to the immune cells, encourage T-reg cell production and stop our immune system overreacting & creating too much inflammation in our systems
Helpful gut bacteria thrive on specific nutrient rich, high fibre foods, also known as prebiotics
A variety of high fibre foods encourages a diverse mix of gut bacteria
Different bacteria eat different foods & produce different helpful SCFAs.
Research shows that the wider the range of beneficial bacteria in the gut, the more types of SCFAs are produced and the less prone we are to allergies & autoimmune diseases, as the inflammation is soothed by the SCFAs.
Eating a variety of foods high in fibre (fiber) is key to encourage a diverse mix of gut bacteria.
If you suffer from IBS or gastric problems, talk your doctor before changing your diet
Nearly all the chemicals present in our bloodstream are made by our microbes.
Research continues into the complex puzzle of how the microbiome and immune system work together & exactly which chemicals are produced by which bacteria.
The good news is that we know enough to start making a difference by eating a varied high fibre diet, to help a wide range of beneficial bacteria thrive in our gut.
The Science Bit
The information I share on this site distills the research I’ve read on the microbiome, prebiotics & probiotics.
You’ll find links to the relevant research studies on each page.
I’m not a scientist / dietician / nutritionist. I’m a food lover & home cook, putting microbiome research findings into action in my kitchen.
Find out more about the scientists leading research into the microbiome on the FAQs page