If you’re looking to improve your immune system, your gut could play an important role. Your gut health and your immune system are closely linked, and changes to one can affect the other.
Your gut is home to thousands of different species of microorganisms — including bacteria, fungi, viruses, and other microbes — collectively known as your gut microbiome. Some bacteria are associated with better health outcomes, others with poorer health outcomes.
A healthy gut microbiome tends to include a wide range of different beneficial bacteria and is vital for a healthy immune system. It plays an important role in regulating your immune system so that it responds to injury or infection but doesn’t attack healthy body tissue.
There are also strong links between your gut health, your immune system, and what you eat.
Scientists from the ZOE COVID Symptom Study recently published the results of the largest study in the world looking at links between diet and COVID-19.
They discovered that people who ate a gut-friendly diet, including lots of plants, were 40% less likely to have severe COVID symptoms or to require hospital treatment than people who ate an unhealthy diet.
As we’ll see below, you may be able to improve the health of your gut microbiome — and your immune system — by regularly eating certain types of foods.
How does your gut health affect your immune system?
Interactions between your gut microbiome and your immune system are complex and work in both directions.
Just as the health of your immune system can influence your gut health, your gut microbiome can have a direct effect on your immune system, including on certain types of inflammation.
When you think about inflammation, you probably think of what happens when you accidentally bruise or cut yourself. The redness, swelling, and heat you may notice as you heal are signs of the cells in the damaged area sending homing signals to specialized immune cells to fight infection and repair the damage.
This is called acute inflammation and is part of your body’s natural way of taking care of itself.
Another type of inflammation is chronic inflammation. Chronic inflammation is a long-term, continuing response by your immune system.
It can affect your health in a negative way, including by increasing the risk of serious conditions like obesity, heart disease, and type 2 diabetes.
Scientists believe that the gut microbiome may be the central player that links chronic inflammation to these diseases.
Over time, eating the wrong types of foods for your body can promote chronic inflammation by causing spikes in your blood sugar and unhealthy blood fat levels.
ZOE’s research has identified 15 “good” bugs and 15 “bad” bugs for gut health. Some of these “good” bugs are associated with lower levels of inflammation.
With the ZOE program, you can discover for the first time which “good” and “bad” microbes live in your gut, and you can discover your personal “gut booster” foods that can help improve your gut health.
Gut microbes and immunity
Scientists are starting to make links between the health of our immune systems and specific gut microbes.
In one study, researchers tracked the progress of 2,000 people whose gut bacteria and immune cell levels had been lowered due to chemotherapy and antibiotics.
The team discovered three “good” bugs that were associated with higher levels of immune cells in the participants’ blood and two “bad” bugs associated with lower levels.
Using computer simulations, the researchers were able to predict that the three “good” bugs would help speed up the recovery of patients’ immune systems.
ZOE’s PREDICT1 study — which has collected nutritional data from over 1,000 people — found similar associations involving one of the “bad” gut microbes identified by ZOE.
ZOE scientists studied the relationships between people’s diets, their levels of white blood cells — which the researchers measured to assess chronic inflammation — and the make-up of their gut microbiomes.
The team discovered that lower levels of pro-inflammatory white blood cells were linked to regularly eating lots of vegetables. They also calculated that 20% of this link was associated with a group of bacteria called Collinsella, which thrive on a diet of processed food.
Why a diverse microbiome is important for your immune system
Research is increasingly revealing important links between a diverse gut microbiome that has many beneficial microbes and a healthy immune system.
In a recent study, scientists looked at the relationships between gut microbiome diversity, diet, and the immune system in two groups of 18 people given special diets over a 10-week period.
One group ate a diet with lots of fiber, while the other was given a diet high in fermented foods containing probiotics. Probiotics are living microbes that can have a beneficial effect on your health.
The high-fiber diet was associated with stable gut diversity. In the group that ate fermented foods, microbiome diversity increased, while markers for inflammation in the body were reduced.
Other research has explored the relationship between our immune systems and the diversity of our gut microbiomes as we get older.
As you age, your gut microbiome becomes less diverse and your risk of infectious disease increases. Although further studies are required, researchers have found some evidence that both probiotics and prebiotics — substances such as fiber that feed the bacteria in your gut — could help to tackle the reduction in gut microbiome diversity.
Using ZOE’s at-home test, you can now learn about the diversity of your own unique gut microbiome, as well as which of the 15 “good” and 15 “bad” microbes that ZOE has identified live in your gut.
What to eat to support a healthy gut
Zoe believes that everyone’s body is different and that you'll achieve the best results for your health by understanding more about your personal responses to food.
However, there are some general tips on what to eat to help support a healthy gut.
Eat lots of plants, which are a great source of prebiotics that feed your “good” gut bacteria. Prebiotics can be found in foods such as:
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asparagus
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onions
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leeks
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garlic
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legumes (like peas, green beans, chickpeas, and lentils)
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whole grains
Eat foods containing probiotics. Probiotics are living microbes found in certain fermented foods that can have a positive effect on your health. They can help to regulate immune responses, including the functions of the gut lining.
Eating them may increase the diversity of your gut microbiome and the amount of “good” bugs it contains — but you need to eat them regularly if you want to see an effect.
Probiotics can be found in fermented foods, including:
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yogurt
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kefir
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kimchi
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sauerkraut
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aged cheddar cheese
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Swiss cheeses like gouda
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cottage cheese with live cultures
You can learn more about which foods to eat in our article on how to improve gut health.
Summary
Your gut health and your immune system are closely linked and can influence one another in a number of ways. This often involves your gut microbiome, the collection of thousands of different species of bacteria and other microorganisms that live in your gut.
Chronic inflammation is a continuing and unhealthy response from your immune system. It is associated with conditions like obesity, heart disease, and type 2 diabetes.
Research suggests that the gut microbiome may be a key player that links chronic inflammation to these diseases.
Eating the wrong kinds of foods for your body can increase chronic inflammation, but ZOE has identified 15 “good” gut bacteria associated with lower levels of inflammation.
Take a quiz to find out how you can learn which “good” and “bad” microbes live in your gut, and which personal “gut booster” foods you should eat to help improve your gut health.
