We’ve all heard that, “you are what you eat,” but this could be more true than we ever thought, when we consider the connections between the immune system and the health of the gut.
Your diet obviously affects the health of your gut, but not many people know that it also affects the functioning of the immune system. Even more fascinating, it all comes down to the trillions of beneficial microorganisms that live inside the gut.
So how can a healthy gut ensure a healthy immune response? And knowing this, what can we do to ensure we have the strongest, most resilient immune systems? To begin, we need to understand exactly what constitutes good gut health in the first place.
What makes a healthy gut?
Living inside the human gastrointestinal tract are trillions upon trillions of bacteria comprising what’s called the gut microbiome. These bacteria can be either “good” or “bad,” but it’s their healthy balance that leads to optimal overall health.
Multiple studies are beginning to show that it’s the gut microbiome that is in control of a wide range of human health aspects, such as cardiovascular health, brain health, and metabolism (1).
The composition of the gut microbiome is in turn influenced by your diet. This makes sense – eating healthy foods supports and nourishes the good bacteria, which can then encourage your total wellbeing.
Certain foods in particular are known to support optimal gut microbial balance, such as fermented foods containing probiotics (good bacteria) like kimchi, yogurt or kefir. Many experts now recommend also taking a probiotic supplement to maintain a good level of healthy bacteria in the gut.
How the gut and the immune system are connected
Broadly, the immune system’s function is to ward off infection from foreign bodies and invading pathogens, defending against disease and keeping the body healthy. The immune system is sophisticated and works well almost always – nevertheless, people do occasionally get sick.
The question of how to support the immune system to do what it does best is a perennial topic in scientific research. If we want to improve our overall immune health, the research has been clear: we need to start with the gut, since there is now a clearly established connection between the gut and the immune system (2).
It’s simple: what you eat directly impacts your health in general and your resistance to infection more specifically. Your diet can change your risk of getting sick.
Bacterial metabolites can affect immune cells
The gut is covered with a barrier that separates it from the rest of the body – the layer of intestinal cells. This barrier has two functions: to keep the contents of the gut inside the gut, but also to transport various needed molecules into the bloodstream once digested. These molecules are all the nutrients, vitamins and minerals that result after food is broken down in the gut. Various metabolites from the bacteria themselves are also released this way. Once in the bloodstream, these compounds can then circulate throughout the body and travel to where they’re needed.
Bacterial metabolites can actually interact with the body’s immune cells once they are mobile in the bloodstream. In this way, bacterial metabolites communicate with and modulate the function of the immune system, affecting the overall response of the body to invasion by pathogens.
The immune system regulates the gut microbiome
There are also some immune cells within the intestinal membrane itself, and they act to transport bacterial microbes into the bloodstream. They also monitor and modulate the gut microbiome composition. By constantly “checking in” on the state of the microbiome, these immune cells act as an early warning system, alerting the rest of the immune system to the presence of pathogens or bacterial threat.
This is what allows the immune system to respond rapidly, ensuring swift and effective functioning to halt any invasions in their tracks, before they spread to the rest of the body. In this way, intestinal wall immune cells are an integral part of the total immune process.
How does a healthy gut support the immune system?
Because of the obvious link between them, we can see just how essential gut health is for supporting immune system health. The gut microbiome directly impacts the health of the gut, which in turn impacts the overall functioning of the immune system.
When the gut bacteria feed and live, they release certain compounds called metabolites. These metabolites are sensed by the immune cells in the gut. If there are more good bacteria, this signal is strengthened and this communication is reinforced, improving the immune response.
How to get a healthy gut
Our diet has a direct influence on the health of our guts, which plays a key role in our immune response. It stands to reason, then, that we improve our immune systems by consuming foods rich in probiotics, i.e. good bacteria. This will support the beneficial bacterial populations in our gut.
Furthermore, we need a healthy diet to support the wellbeing of the bacteria already living in the gut. Fatty, over processed and sugary foods only encourage the growth of harmful bacteria, which then release toxins and undermine our health. Supplements are also useful, and can boost probiotic levels as well as add vital mineral, vitamins and other nutrients for good health.
When our gut microbiota are healthy and balanced, they release more metabolites that are detected by the body, which enhances the sensitivity of the immune system in general. On the other hand, an excess of harmful bacteria can disrupt this process, causing an elevated risk of infection and disease, and increase in inflammation and corresponding chronic health conditions (3).
Research showing the effect of the gut on the immune system
A University of Arizona scientific review found that the gut microbiome composition significantly influences the body’s immune response (4). They discovered that the microbiome was actually implicated in the development of many autoimmune diseases, among other interesting observations.
A separate scientific study found that things like supplement use and diet, as well as other environmental factors, substantially affect the microbiome (5). The kinds of foods that people eat in particular were found to influence microbiome composition, with unhealthy diets predisposing to bacterial imbalances – which then negatively influence immune system function.
The Takeaway
The human gut hosts a vast quantity of microbacteria, both good and bad, which are vital for the digestion of food and impact every aspect of health. In digesting our food, they release key compounds into the bloodstream that communicate directly with the immune system via specialized immune cells.
It comes down to the overall microbiome composition; when the gut bacteria are balanced and healthy, the immune system functions optimally, helping you achieve complete physical wellbeing – and freedom from disease and infection.
