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Digestion and Immunity – 5 Tips to Boost Your Defences Right NOW

If the pandemic has taught us anything it’s the importance of a properly functioning immune system. But while there’s plenty of talk in the media about the link between immunity and supplements such as Vitamin D and Echinacea, the role of the digestive system is often overlooked – despite the fact that it plays an intrinsic role in the body’s system of defence.

Did you know, for example, that the gastrointestinal tract is home to a staggering 70% of your entire immune system?(1) In fact, some scientists believe that the two systems share a common origin, appearing early in the evolution of Metazoa to simultaneously fulfil the needs of defence and nutrition.(2) Despite this, little effort is made in the western world to improve digestion for the sake of immunity and although Doctors are finally waking up to the role that poor diet plays in the development of disease, the effect it has on digestion (and subsequently immunity) has yet to enter the narrative.

So what’s going wrong?

The answer to this lies deep in the open spaces of our large intestines, home to the fabled microbiome. This fantastically complex ecosystem plays host to trillions of bacteria, fungi and viruses, which collectively perform the unenviable task of regulating our entire immune system. As with any ecosystem there is a delicate balance of power, with hundreds of ‘helpful’ bacteria species competing for supremacy with less favourable organisms. The problem with modern lifestyles and diets is that they often inhibit the growth of ‘helpful’ bacteria, leading to a decline in both population density and species diversity.

As Dr Michael Mosely argues in his excellent book The Clever Guts Diet, one of the main issues is that we eat such a narrow range of foods. “Of the 250,000 edible plant species,” he explains, “we use less than 200. Seventy-five percent of the world’s food comes from just 12 plants and 5 animal species.”(3) With stats like these, it’s no wonder our gut bacteria are in decline – they’re living on a restricted diet!

The other major contributing factor to the decline of our microbiota is our obsession with ultra-processed foods. Defined as any food substance that has gone through multiple stages of industrial processing and/or containing large numbers of artificial additives, Ultra Processed Foods (UPF’s) have become increasingly popular over the past 30 years. In the 1980’s for example, the average UK diet consisted of 58% fresh ingredients and 26% ultra-processed foods, but by 2000 this ratio had virtually reversed with just 28% of the diet constituting fresh foods and 44% ultra-processed. In 2021 the situation is even worse, with UPF’s comprising nearly two thirds of the calories we consume.(4)

The Link between Ultra Processed Food, Poor Digestion and Immunity 

Ultra-processed foods are bad for digestion for 2 reasons. Firstly, they contain very little in the way of nutrition for friendly gut bacteria – being generally low in prebiotic fibre and derived from a limited number of industrial proteins, grains and fats. Secondly, they contain a large number of artificial additives – several of which (including emulsifiers) have been proven to actively inhibit microbial richness. (5) 

Given the vital role that the microbiome plays in regulating digestion and immunity it’s little wonder that increased consumption of UPF’s over the past 30 years has coincided with skyrocketing rates of obesity, digestive disorders and other non-communicable diseases.

So what can we do? 

Quite simply, we need to improve the health of our microbiome – specifically by promoting the growth of friendly bacteria and encouraging a diverse range of species to develop. 

Below, we outline our top 5 tips to naturally enhance microbial richness, improve digestion and subsequently give your immune system a much-needed boost.

5 Tips To Boost Digestion and Supercharge your Immune System

1. Avoid Ultra Processed Foods.

There are countless reasons to reduce the amount of ultra-processed food in your diet but its effect on your microbiome is among the most important. Eliminating UPF’s entirely may be a tall order given their prevalence in western culture but a diet focused mainly on whole foods (with plenty of fresh fruits and vegetables) is a great starting point. Common UPF’s include mass produced bread, breakfast cereals and most pre-packaged ‘ready’ meals.

Tip: Try to limit UPF’s to 10% or less of your total calorie consumption.

2. Add Diversity

It’s no coincidence that hunter-gatherer civilisations such as the Hadza tribe from Tanzania have some of the healthiest microbiomes on earth. Unlike most of us, they eat an incredibly diverse range of foods including foraged fruits, fibre-rich vegetables and wild fish and game. Notably, their processed food consumption is virtually zero. While it might not be possible to mirror the diets of the Hadza exactly, adding a little diversity (specifically by incorporating a wide range of fresh fruits and vegetables) can have a big impact on the health of your microbiome. 

Tip: Aim for 5-7 portions of different fruits and vegetables every day, choosing organic, locally grown produce wherever possible.

3. Exercise regularly (especially outdoors).

It’s well-established that regular exercise offers countless health benefits, but did you know that it can also enhance the number of beneficial bacteria in your gut? A recent study conducted by the department of Experimental Medicine in Naples concluded exactly that, stressing that exercise can even be used “as a treatment to maintain the balance of the microflora or to rebalance its eventual dysbiosis.”(6)

You can further enhance the benefit by exercising outdoors. Getting outside and away from sterile internal environments exposes your body to all sorts of helpful organisms that can positively impact your microbiome.

Tip: Exercise for at least 30 minutes 5 times per week. At least 2 of these sessions should be outdoors.

4. Limit alcohol (but don’t abstain completely).

We all know that excessive alcohol is bad for our health and unfortunately this extends to the microbiome as well. However, research from The American Gut Project at the University of California suggests that people who consume at least one alcoholic drink a week have a more diverse microbiome than those who abstain completely. (7)

As with food, the choice of alcoholic drink is important and anything mass produced is best avoided as it is likely to be heavily processed. Opt instead for small quantities of Organic red wine, locally distilled spirits or even home-brew beer and cider.

Tip: Limit alcohol to 3-4 drinks per week. Choose organic, small-batch alcohol wherever possible or even make your own!

5. Try Probiotics.

If you’re struggling to add diversity to your diet, or if you’ve tried the other steps without success, supplementing with probiotics is a great way to improve the health of your microbiome and support its role in regulating immunity. There are countless probiotic supplements on the market, each utilising different strains of bacteria, but our favourite species for immune support are: Bifidobacterium Bifidum and Lactobacillus Acidophilus.

Tip: Introduce a quality probiotic supplement as part of your daily routine. Opt for one that contains at least 10 billion CFU’s (colony forming units) per serving.  

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The digestive system plays a vital role in the regulation of immunity and the prevention of disease. At the core of this system lies the microbiome, which can be both positively and negatively influenced by our diets and lifestyles. There is growing evidence that poor diets (specifically those low in plant-diversity and high in Ultra Processed Foods) are fuelling a sharp decline in the health of our microbiomes and subsequently the function of our immune systems. By addressing these imbalances and taking active steps to improve the quality of our diets, we can stimulate the growth of friendly bacteria species in our gut and limit our exposure to the epidemic of non-communicable diseases affecting modern society.




(3) Mosely, Michael. The Clever Guts Diet. Short Books. 2017. 






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