Gut health and immunity – what you need to know
Wondering how our gut health can influence our immunity?
The gut microbiome (sometimes known as the gut microbiota or flora) describes the trillions of microorganisms living in our gut. Most of these tiny tenants are strains of bacteria, but some are viruses or species of fungi. We’ve learnt to associate words like ‘bacteria’ with infection, uncleanliness and illness but this isn’t always the case. In fact, our ‘good’ bugs work day-to-day to keep ‘bad’ bugs out. What’s more, it’s a battle that’s taking place all over our bodies.
While our gut flora refers to the collection of bugs that have made their home in our gut, microbes also live in our mouth, eyes, vagina and on our skin. Though individual bugs are microscopic, collectively they are mighty. Our total bug-count weighs in at 1.2kg, similar to the weight of the human brain!
Gut health and its impact on our immunity
Almost 70% of the immune system resides in the gut. Here, microbes are our first line of defence against any threats we eat (like food a little past its use-by date). They also keep our defensive stomach juices nice and acidic by fermenting the fibre in our diet.
Our good gut bugs supply the immune system with all the short-chain fatty acids (SCFAs) it needs to produce our white blood cells. Studies show that interventions in gut health could reverse allergies, reduce our likelihood of getting a cough or cold in cooler months, and may even offer some protection against autoimmune diseases.
Our gut bugs also play a key role in early life. They teach us to recognise friend from foe and (if all goes well) help us to move into adulthood with a balanced immune system.
Weight and immunity
We also know that carrying excess weight impairs our immunity and could increase our risk of a cytokine storm. What is lesser known is that our gut health has a huge role to play in whether or not we pile on the pounds. A study of 12,000 children found that those given antibiotics in the first six months of life had a greater chance of being overweight than those not exposed. This early antibiotic exposure damages the gut flora, leaving us more vulnerable to weight gain.
Not only that, but researchers have identified specific strains of ‘obese’ and ‘lean’ gut bugs. When microbes associated with obesity were transplanted from obese mice into lean mice, these mice rapidly gained weight despite being given exactly the same quantities of food. In contrast, lean individuals have been shown to have diverse portfolio of gut bugs in their tummies, with significantly higher levels of bugs known as Akkermansia and Christensenella.
A bad bug balance may also disrupt our blood sugar levels. This is another key marker when it comes to measuring metabolic health and immunity. This is due to the chemicals (or ‘postbiotics’) our bugs produce while digesting food. While we’d hope that our bugs would produce lots of lovely anti-inflammatory SCFAs, researchers have shown that some undesirable species produce chemicals called lipopolysaccharides (LPS). When given to mice, LPS has been shown to trigger both weight gain and blood sugar imbalance. On the flip side, both Bifidobacteria and Akkermansia bugs help maintain a normal gut barrier ensuring inflammatory chemicals (like LPS) cannot leak from the gut into the bloodstream.
Find out more about immunity in Liz’s guide
Do you know your leukocytes from your lymphocytes? This guide dives into the science of our under-appreciated immune system. Liz also shares her secrets to staying well and achieving a beautifully balanced immune system.