Here's why you should take care of your gut health at flu season

Your gut does much more than digest food. It is home to trillions of microorganisms and forms an important interface between the outside world and your immune system.

This makes the relationship between gut health and immunity particularly interesting during autumn and winter, when many of us start thinking more about supporting our body's normal defences.

But how exactly are the gut and immune system connected? In this guide, we explore the gut-immune connection, the role of the gut microbiome and the everyday habits that can help support both gut health and normal immune function.

How Are Gut Health and the Immune System Connected?

The gastrointestinal tract is constantly exposed to food, microorganisms and substances from the outside environment. As a result, it needs to distinguish between substances that are harmless and those that may represent a potential threat.

A substantial proportion of the body's immune tissue is associated with the gut. This specialised system helps the body respond appropriately to microorganisms while tolerating food components and the beneficial microbes that normally live in the digestive tract.

The gut and immune system therefore communicate continuously. Rather than working as two separate systems, they form part of an interconnected network involving the intestinal barrier, immune cells and gut microbiome.

What Is the Gut Microbiome?

The gut microbiome is the community of microorganisms that live throughout the digestive tract. It includes many different species of bacteria as well as other microorganisms.

These microbes interact with the food we eat and with our intestinal environment. Some gut bacteria can ferment dietary fibre and produce compounds known as short-chain fatty acids.

The composition of the gut microbiome differs from person to person and can be influenced by factors such as diet, age, lifestyle, medication and environment.

How Does the Gut Microbiome Interact With Immunity?

The gut microbiome and immune system exist in close contact with one another.

Beneficial microorganisms can interact with the intestinal barrier and immune cells, while the immune system helps maintain an appropriate relationship between the body and the microorganisms living in the gut.

This communication helps explain why researchers increasingly study the gut microbiome as part of the wider immune system.

However, gut health is only one factor involved in immunity. Sleep, nutrition, physical activity, age, stress and overall health also influence how the immune system functions.

Why Is the Intestinal Barrier Important?

The lining of the digestive tract forms a physical barrier between the contents of the gut and the rest of the body.

This barrier needs to perform two seemingly opposite tasks: allowing nutrients to be absorbed while helping prevent potentially harmful substances and microorganisms from entering the bloodstream.

The intestinal mucus layer, epithelial cells, immune cells and microorganisms living in the gut all contribute to this complex protective environment.

Does Gut Health Matter During Cold and Flu Season?

A healthy gut forms part of overall health throughout the year, not only during cold and flu season.

However, autumn and winter are often periods when people spend more time indoors and respiratory infections circulate more frequently. This makes supporting normal immune function particularly relevant.

No food, probiotic or supplement can guarantee that you will avoid a cold or flu. Instead, focus on providing your body with the foundations it needs for normal immune function, including a varied diet, adequate sleep, regular movement and appropriate intake of essential nutrients.

How Can You Support Your Gut Health?

There is no single food or supplement that creates a "perfect" microbiome. Instead, your everyday dietary and lifestyle patterns matter.

1. Eat Plenty of Fibre

Dietary fibre is found in plant foods such as vegetables, fruits, legumes, whole grains, nuts and seeds.

Different types of fibre behave differently in the digestive system, which is one reason why eating a wide variety of plant foods can be beneficial.

Some fibres can be fermented by gut bacteria and used to produce short-chain fatty acids.

2. Include Fermented Foods

Fermented foods can be an interesting addition to a varied diet. Examples include:

• Yoghurt with live cultures
• Kefir
• Sauerkraut
• Kimchi
• Other traditionally fermented vegetables

Not every fermented food contains live microorganisms by the time it is consumed, so the nutritional characteristics can differ between products.

3. Eat a Diverse Diet

Your gut microbiome is itself highly diverse, and different microorganisms thrive on different dietary components.

Rather than concentrating on one supposed "gut superfood", aim for variety across vegetables, fruits, whole grains, legumes, nuts and seeds.

4. Stay Physically Active

Regular movement supports overall physical and mental wellbeing and can also support normal digestive function.

Walking, cycling, swimming, strength training and other activities you enjoy can all form part of a healthy routine.

5. Prioritise Sleep

Sleep is another important part of immune health. Maintaining a consistent sleep routine and allowing enough time for rest can help support normal physical and psychological function.

6. Make Time for Recovery

The gut and brain communicate continuously through what is commonly known as the gut-brain axis.

Stress can influence digestive function, appetite and eating habits, which makes recovery an important part of a gut-friendly lifestyle.

Walking outdoors, breathing exercises, yoga, reading or simply taking regular breaks can all help create moments of calm.

Which Nutrients Support Normal Immune Function?

A varied diet provides numerous nutrients involved in normal immune function. Several vitamins and minerals have particularly well-established roles.

Vitamin C

Vitamin C contributes to the normal function of the immune system. It also contributes to the protection of cells from oxidative stress and the reduction of tiredness and fatigue.

Food sources include citrus fruits, berries, peppers, broccoli and other fruits and vegetables.

Vitamin D

Vitamin D contributes to the normal function of the immune system. It also contributes to the maintenance of normal bones and normal muscle function.

The body can produce vitamin D through exposure of the skin to sunlight, while smaller amounts can be obtained from certain foods.

Zinc

Zinc contributes to the normal function of the immune system and to the protection of cells from oxidative stress.

Zinc can be found in foods including meat, shellfish, dairy products, legumes, nuts and seeds.

Vitamin B6

Vitamin B6 contributes to the normal function of the immune system. It also contributes to normal energy-yielding metabolism and the reduction of tiredness and fatigue.

What Are Probiotics?

Probiotics are live microorganisms found in certain foods and food supplements.

Different probiotic products can contain different microorganisms, species and strains, which means they should not automatically be considered interchangeable.

This distinction is important when reading research about probiotics because findings relating to one specific strain or combination of strains cannot necessarily be applied to every probiotic product.

Do Probiotics Strengthen the Immune System?

The relationship between probiotics, the microbiome and immune function is an active area of research.

However, it is too broad to say that probiotics in general simply "strengthen" or "boost" the immune system. Effects can depend on the specific microorganisms and strains studied, as well as the population and outcome being investigated.

For everyday wellbeing, focus first on the foundations of gut health: a varied diet, sufficient fibre, regular movement, adequate sleep and healthy lifestyle habits.

Frequently Asked Questions About Gut Health and Immunity

Is the gut connected to the immune system?

Yes. The gastrointestinal tract contains extensive immune tissue, and immune cells interact continuously with the intestinal barrier and microorganisms living in the gut.

What is the gut microbiome?

The gut microbiome is the community of microorganisms living in the digestive tract. Its composition varies between individuals and is influenced by factors including diet, age, lifestyle, environment and medication.

What foods support gut health?

A varied diet containing vegetables, fruits, legumes, whole grains, nuts, seeds and other fibre-rich plant foods provides substrates used by different gut microorganisms. Fermented foods can also form part of a balanced diet.

Does fibre support the gut microbiome?

Some types of dietary fibre can be fermented by gut bacteria. Eating a variety of fibre-rich plant foods can therefore help provide different substrates for microorganisms in the gut.

Can probiotics prevent colds or flu?

Probiotics should not be considered a guaranteed way to prevent colds or flu. Research into individual probiotic strains and immune-related outcomes continues, but effects cannot automatically be generalised across all probiotic products.

Which vitamins support the immune system?

Several nutrients contribute to normal immune function, including vitamin C, vitamin D, vitamin B6 and zinc. These nutrients should ideally form part of an overall balanced and varied diet.

Supporting Your Gut and Immune Health Every Day

The connection between the gut and immune system is complex, but the foundations for supporting both are surprisingly simple.

Eat a varied and fibre-rich diet, move regularly, prioritise sleep and give your body enough time to recover. Nutrients such as vitamin C, vitamin D, vitamin B6 and zinc also contribute to normal immune function.

Rather than focusing only on your gut during cold and flu season, think of gut health as something worth supporting throughout the year.