Alexandra Falconer | 17 Jun 2020 | Gut Health

What has Gut Health Got To Do With Immunity?

Before the coronavirus pandemic, like most of us, you probably only ever thought about your immune system when the winter cold season hit. But with experts in the media telling us how crucial a healthy immune system is in the fight against Covid-19, immunity is now a hot topic.

You’ve probably heard that your gut and your immune system are inextricably linked. But the truth is that—for the most part—the two are not only connected, but actually the same.

So if you want to find out about gut health, immunity, and how having healthy gut bacteria means so much more than just having a healthy digestive system, read on.
Back to top


How your Gut Health Affects your Immune System
How Much of your Immune System is in your Gut?
How Probiotics Could Help your Immune System
The Best Probiotics for your Immune System
How You can Boost your Gut and your Immune System
Can you build up your immune system?

How your gut health affects your immune system

The latest research tells us that immunity starts with your gut (Source: NCBI).

Scientists are finding that your gut microbiome (the 100 trillion bacteria, viruses and other microbes that live in your gut) is one of the primary directors of your body’s immune response. It appears that the gut has an immune system all of its own: intestinal bacteria and microbes working together, communicating with your body systems to rally the troops when they’re needed to mount an attack (Source: FRONTIERSIN).

So a healthy gut microbiome is the foundation of your overall wellness, triggering your body’s immune response when it detects invaders.

We know that there’s a connection between the type and combination of microbes in your gut and your risk of disease, and how your body responds to invading bacteria and viruses (Source: NCBI). We just don’t know enough about that connection yet to make definite conclusions.

For example, initial research has told us that:

  • babies that grow up with dogs have a more diverse microbiome, which helps to prevent the development of immune disorders like allergies and asthma (Source: NCBI)
  • changing just one species of gut bacteria can affect the symptoms of autoimmune disorders like endometriosis, type 1 diabetes and ulcerative colitis (Source: NCBI)
  • switching from a low-fat, plant-based diet to a high-fat, high-sugar diet can alter the microbiome in one day, leading to obesity in just two weeks (Source: NCBI)

Free symptom review consultation


Back to top

How much of your immune system is in your gut?

Seventy to eighty percent of the total amount of immune cells in your body live in your gut, in a tissue known as ‘gut associated lymphoid tissue’ (GALT) (Source: NCBI).

So apart from your microbiome—a dynamic, living community of microbes in your gut that directs your immune processes—your actual body cells that carry out those processes are also in your gut.

This testifies just how crucial your gut is when it comes to immunity. GALT participates in the activities of your gut in many ways: for instance, by increasing intestinal permeability (leaky gut) in response to a particular food, or sometimes by provoking damage to the intestinal mucosa, as with coeliac disease or food allergy (Source: NCBI).
Back to top

infographic gut health coronavirus

How could probiotics help your immune system?

In a recent review of current research, a group of scientists concluded that probiotics show potential for helping several immune response-related diseases, such as allergy, eczema and viral infections.

They also found that certain strains of probiotics can regulate the functions of immune cells in our gut and other places in our bodies (Source: NCBI).

It’s important that the bacteria in probiotics can survive through the gastric juices and bile in our stomachs and guts to be able to multiply and set up home (Source: NCBI). A lot of commercial probiotics in supermarkets and chemists haven’t been tested for this, so do your research when you choose a probiotic supplement.

One of the ways probiotics support immunity is by fighting off less-friendly bacteria. Probiotics use the same nutrients to grow and thrive as pathogens, or ‘bad’ bacteria. Several studies have shown that probiotics like L. rhamnosus GG and L. plantarum can stop pathogenic strains of E. coli from taking hold in our guts (Source: PUBMED).
Back to top

The best probiotics for your immune system

Right now, we don’t have any proof that any one probiotic is better for your immune system than any other. It’s likely that your response to any probiotic is down to your own body chemistry and the mix of microbes already in your gut.

However, one study did find that the combination of probiotics Lactobacillus paracasei, Lactobacillus casei 43 and Lactobacillus fermentum PCC could lower your chances of getting an upper respiratory infection. In this case, the probiotics worked by increasing the level of one substance, known as ‘interferon type 1’ in the blood, and another—’secretory IGA’—in the gut (Source: NCBI).

These probiotics have a fair weight of evidence behind their potential to support your immune system (Source: PUBMED).

  • Lactobacillus rhamnosus GG
  • Lactobacillus casei Shirota
  • Bifidobacterium animalis Bb-12
  • Lactobacillus johnsonii La1
  • Bifidobacterium lactis DR10
  • Saccharomyces cerevisiae boulardii

Diversity, diversity, diversity

Probiotics could be a great way to boost your gut health, and by default, support your immune system. But probiotic supplements usually only contain a few different types of bacteria, so while they’re a great tool, a lot of experts agree that when it comes to your microbiome, diversity is key: the more families of bacteria in your gut, the healthier you’re likely to be (SOURCE: PUB MED), (SOURCE: PUB MED).

Is your gut is home to bountiful, thriving ecosystem of bacteria and other microbes? Or is it more of a microbial monopoly? If you’d like to find out, take one of our stool tests to get a window into your gut health.

The test includes insights into:

  • your gut pH levels, microbial diversity, your enterotype, and your levels of dysbiosis
  • the different types of bacteria you’re habouring
  • presence and levels of yeasts (including candida), moulds, parasites, and pathogenic bacteria
  • digestive function, immune system markers and inflammation
  • (bonus) leaky gut: zonulin levels
  • (bonus) worms and eggs: identify helminths, especially useful after bouts of food poisoning

Free symptom review consultation


Back to top

How you can balance your immune system by boosting your gut health (and vice-versa)

‘Boosting’ your immune system has become a bit of a buzz-phrase. While it sounds snappy, it’s not a very accurate reflection of how your immune system works.

You can’t really turn your immune system up or down: it’s too complex for that, and even if you could, you wouldn’t want to. When you have an infection—a virus, bacteria or something else—some of the most debilitating symptoms happen because your immune system is working on overdrive. So it’s not the infection causing you pain, it’s your immune system.

This is how your immune system works: it’s how it fights the thing infecting you, but while it’s doing that, it can cause pain and discomfort (like a temperature, headache or rash, for instance). Long term, it can also damage your body: people who have autoimmune conditions, like endometriosis or Crohn’s disease, know this. Autoimmunity happens when your immune system overreacts to an infection, or ‘thinks’ it needs to fight one when it isn’t there at all.

Balance, don’t boost

So, you don’t need a ‘boosted’ immune system. You need a balanced one. Your body needs to respond appropriately to threats, while not overwhelming you with the symptoms of an immune attack.

Because of the massive overlap between your gut and your immune system, anything you do to get your gut healthy will likely balance your immune system too.

This works in reverse too: any advice you’ve heard on how to balance immunity probably works—at least partly—through your gut.

Vitamin C

This immune system superstar is necessary for tissue repair and cell growth (Source: NCBI). It also helps with the absorption of iron. Most fruit and vegetables contain vitamin C, but green leafy vegetables, like spinach, are powerhouses too.

  • citrus fruits
  • kiwis
  • peppers
  • thyme
  • parsley

Vitamin B6

This vitamin has a hand in so many vital biological functions. Both your digestive system and your immune system rely on vitamin B6 to help transform food into energy (Source: NCBI).

  • salmon
  • chicken
  • green leafy vegetables
  • Chickpeas

Vitamin E

This vital antioxidant helps to prevent infection and cell damage (Source: NCBI). It may also help repair the gut lining (Source: PUBMED).

  • broccoli
  • spinach
  • peanuts
  • almonds
  • sunflower seeds


Iron is a food source for many friendly gut bacteria and helps your immune system find and kill harmful bacteria and viruses (Source: NCBI).

  • red meat
  • broccoli
  • kale
  • beans
  • poultry
  • seafood

Selenium and zinc

These two essential minerals actually slow the body’s immune response, which is a good thing, as an overactive immune system results in inflammation. They also repair damage to cells (Source: PUBMED).

Zinc is found in oysters and beans.

Nuts, mushrooms, and garlic contain selenium.
Back to top

Can you build up your immune system?

The best place to start building up your immune system is your gut. Let’s look at the three Fs for a healthy gut:

Fill up on fibre

Your gut microbes feed on fibre. To get and keep a healthy digestive system, include it with every meal: put a wide range of veg in a variety of different colours on your plate, such as:

  • berries
  • kiwis
  • beans
  • lentils
  • onions
  • garlic
  • nuts and seeds

Ferment your food

Fermented foods are usually richer in probiotic bacteria than probiotic supplements. In your quest for a healthy bowel, why not try:

  • live yogurt
  • sauerkraut
  • kimchi
  • raw apple cider vinegar
  • kombucha
  • kefir

Fast to feel hungry

Eating nothing for up to 16 hours (overnight counts, so try eating dinner early and breakfast a little later the following day) or following the 5:2 diet where you eat just small amounts two days a week, allows your gut to heal and restore itself (Source: NCBI).

In our culture, we’ve become used to instantly squashing our hunger with snacks, but we know from looking at traditional cultures that this isn’t how human beings evolved.

A recent review of research (Source: NCBI) highlighted the ways that fasting can improve gut health.

Fasting has the potential to:

  • cleanse cells of accumulated toxins and waste products
  • strengthen the gastrointestinal mucosal lining
  • improve digestion
  • reduce oxidative damage
  • reduce inflammation
  • improve metabolism
  • balance the gut microbiome

The bottom line? Our guts and our immune systems are so interwoven, you can’t support one without supporting the other. Good gut health equals good immune health. When you take care of your gut, you take care of your immune system too.

Free symptom review consultation


Back to top

Key takeaways

  • Most of the immune cells in your body—seventy to eighty percent—are in your gut. That means that your immune system isn’t just connected to your gut. It is your gut, and vice versa.
  • Your microbiome plays a massive role in directing your immune system: research is starting to show that a diverse microbiome protects against allergies, immune disorders and more.
  • Certain types of probiotics could protect us against some diseases, but we need more research.
  • To boost your immune system (and your gut too), look after your gut with the three Fs: fibre, fermented foods and fasting.

Back to top

Alexandra Falconer MA (Dist) DipCNM mBANT is a Registered Nutritional Therapist specialising in IBS and related conditions. A graduate of Brighton’s College of Naturopathic Medicine, she is committed to fighting the root causes of chronic illness and bringing functional medicine to everyone who needs it.

Before her natural health career, Alex was a journalist and copywriter. She continues to write for magazines and media agencies, and now combines her two great passions—writing and health—by creating content that empowers people to claim their right to a healthy body and mind.

Other articles you might like


Interest free monthly payments

The benefits of choosing Splitit

  • No credit check
  • 0% interest
  • Never any late fees
  • No application or registration
  • Instant approval
  • Works with your existing credit

How Splitit works

Splitit Choose splitit at Checkout
Splitit Select number of payments
Splitit Order Complete


At the time of purchase, you will only be charged for the first payment. On the same day of the following month your card will be charged the second payment and so on for each remaining month of the purchase plan.

To be eligible, you must own a Visa or Mastercard credit or debit card and have the entire amount of your purchase available on your card at the time of authorisation.

Debit cards have a maximum transaction value of £400 per transaction. If you require to spend over this amount, you may carry out two transactions. Credit cards have no maximum.

Splitit works by pre-authorising you payment card and then splitting the payment down into monthly charges. There is no extra charge for this service.