How to support a healthy immune system through your gut

Can our food choices really affect our immune system? Dr Linia Patel shares how to support your gut health.

Did you know that there are more bacterial cells in your body than human cells? To be more exact, there are roughly 40 trillion bacterial cells in your body and only 30 trillion human cells. This means that you are more bacteria than human. Most of these bacteria are found in a pocket of your large intestine called the cecum and they are referred to as your gut microbiome. Your microbiome plays an important role in your wellbeing, your health and how strong your immune system is.

How does the gut support a healthy immune system? (1,2)

Over 70% of the body’s immune system lives in the gut. The gut microbiome controls how well your immune system works. Initial research showed that the gut microbiome stimulates the immune system’s response to infection and supports the production of immune antibodies which fight the virus. However, research also suggests that the bacteria don’t do all the heavy lifting when it comes to interacting with the immune system. In fact, they have assistants: the metabolites they produce when they break down the fibre we eat. Chief among them are short-chain fatty acids (SCFAs) such as butyrate. Butyrate, for example, seems to be responsible for communicating with immune cells on how your body responds to infection. Some studies also show that these SCFAs lend a helping hand to immune-modulating regulatory T cells that also tune down inflammation.

Gut health care

Although the research to date only scratches the surface, we do have some science-based ways to alter immune function by taking care of your microbiome. Here are some tips:

Don’t cut out carbs: (3,4) Our gut contains around 1,500 species of bacteria and study after study is increasingly showing how important it is for our waistline and health if we maintain a high diversity of bacteria. To maintain this high diversity, you need to ensure that you include carbs in the form of wholegrains and fruit and vegetables. Within these types of carbohydrates are types of fibre that are known to have a ‘prebiotic’ effect. That means they feed the ‘good’ bacteria, therefore enriching your gut microbiota. Current dietary guidelines recommend that we eat about 30g of fibre per day; however, most of us are only eating about 19g. Fibre is an underrated nutrient, yet in fact it is a Holy Grail nutrient. If you can increase the amount you eat, it will not only benefit your gut function and your immune function, but will also have a positive impact on your waistline, your heart and pretty much every organ in your body.

Mix up the routine: (5,6) Routine kinda person when it comes to food? If it’s a yes, then the chances are that the diversity of your diet is low. In fact, studies have shown that if you are having fewer than 10 plant-based foods (nuts, wholegrains, legumes, fruit and vegetables) every week, your microbial diversity isn’t very strong. You need to eat as wide a range of plant-based foods as possible. Recent research suggests that you need to aim to eat at least 30 different plant-based foods each week. Don’t just fixate on eating the same things all the time. So, if you regularly eat wild rice, try another ancient grain like spelt or quinoa or buckwheat. Better still, buy a mixed grain. The same goes for cans of beans. Great if you always add a can of chickpeas to your weekly shop – how about swapping this for a four-bean mix instead? Try lentil, bean or wholewheat versions of pasta. Buy in-season fruit and veg, which means you won’t always be eating the same things.

Eat fermented foods: (7,8) The process of fermenting involves bacteria and yeast, so it makes sense that increasing your intake of fermented foods has a positive impact on your gut microbiome. Fermented foods could provide health benefits beyond basic nutrition. Scientists are still investigating exactly how they affect our bodies and health. Some studies have linked the intake of fermented foods to a reduced risk of cardiovascular disease, type 2 diabetes and better gut health. Kefir is one of the fermented foods that has the most research behind it. It has around 20 different types of bacteria and yeast in it, making it a great addition to your diet. However, there is a range of different types of foods, such as bio-live yogurt, kimchi, sauerkraut, miso, tempeh and sourdough bread, that is also believed to be beneficial to the gut.

Sleep on it. (9) Good-quality, refreshing sleep is good for your gut. More and more research is showing that the better we sleep, the more flourishing our gut microbiome will be and vice versa. The sleep-gut link is complex; however, a recent study shows that, after two nights of sleep deprivation, there were significant decreases in the types of beneficial bacteria.

Chill out. (10) Learning to chill out is key to keeping your microbiome balanced and diverse and, in turn, helping to support your immune system. When you stress out, your body releases stress hormones, which in turn cause your immune system to release inflammatory cytokines. These cytokines send inflammation messages to all parts of your body, including your gut bacteria. Over a long period of time this has a negative effect, increasing the leakiness of your gut and causing an unbalanced microbiome.

This previously featured in the Fitpro digital magazine.

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About the author

Dr Linia Patel has a BSc degree in biochemistry and physiology and has recently achieved a PhD in public health. Linia is a leading dietitian and sports nutritionist. Her passion is translating nutritional science into easy-to-digest and practical advice.

References

Rooks et al (2016), Gut microbiota, metabolites and host immunity, Nat Rev Immunol., 16(6): 341-52.
Levy et al (2017), Dysbiosis and the immune system, Cell, 17(4): 219-32.
Wastyk et al (2021), Gut-microbiota-targeted diets modulate human immune status, Cell, 184(16): 4,137-53.e14.
Makki et al (2018), The impact of dietary fiber on gut microbiota in host health and disease, Cell Host Microbe, 13: 23.
Zmora et al (2017), You are what you eat: diet, health and the gut microbiota, Nat Rev Gastoenterol Hepatol.,16.
Singh R (2017), Influence of diet on the gut microbiome and implications for human health, J Transl Med., 73.
Shen T (2017), Diet and gut microbiota in health and disease, Nestle Nut Inst Workshop Ser., 88: 117-26.
Ma N et al, Contributions of the interaction between dietary protein and gut microbiota to intestinal health, Curr Protein Pept Sci., 795-808.