The body's immune system: Defense from the gut

The intestine - more than a digestive organ

The intestine as the largest organ of our body has attracted the attention of scientists in recent years - and rightly so. For years, it was believed that it was only responsible for digesting our food and absorbing nutrients. However, the results of research are powerful. The intestine forms the center of our health. In addition to digestion, it communicates over the Gut-Brain Axis With our brain and clearly has the upper hand here. It even determines our hunger, our mood, and even more importantly: the gut also plays a role in the immune defense. Because it has its own immune system - around 70 percent of immune cells are located in the intestinal mucosa.

The gut and its immune system: GALT

The gut-associated lymphoid tissue (GALT) describes the gut-associated immune system. It is located in the intestinal wall and represents the largest collection of immune cells in the body: around 70 percent of defense cells are located here. Its task is to defend against pathogens and unwanted foreign substances. At the same time, the GALT must recognize and tolerate the body's own cells, nutrients, and the bacteria of the normal intestinal flora. Therefore, it must distinguish between "good" and "bad".

The immune cells are stored in the so-called Peyer's patches, which are small lymph nodes. They communicate with the rest of the immune system through the blood and lymphatic system, thus providing information about pathogens to all other defense centers of the body. Therefore, the intestine influences the entire body's immune defense.

Defense support of the small intestinal mucosa

But not only the gut-associated lymphoid tissue (GALT) is important for the body's own defense. The intestinal mucosa of the small intestine is also part of the central defense system of the gut. In addition to the cells that serve for nutrient absorption, the mucosa of the small intestine also consists of other cells that defend against intruders: These include, among others, Paneth and M cells. Paneth cells respond to viruses, bacteria, fungi, or parasites by releasing certain substances upon contact to combat them. In contrast, M cells are able to uptake the pathogens and transport them to the specific defense cells to support the immune system.

All good things come in threes: gut flora

But the gut wouldn't be the center of our defense if it didn't have another ace up its sleeve: our gut flora. In our colon, trillions of microorganisms ideally live peacefully in harmony with each other, forming our gut flora. It also consists of "good" and "bad" bacteria. This is not a problem as long as the "beneficial" ones prevail. Because they actively work in defending against pathogens:

• On the one hand, beneficial gut bacteria compete with pathogens for "food," and on the other hand, they consume the oxygen that many disease-causing bacteria need. This prevents pathogenic germs from spreading and gaining the upper hand in the gut (colonization resistance).

• The intestinal bacteria break down indigestible food components (fiber), resulting in short-chain fatty acids. These strengthen the cells of the colon and thus have a protective effect on the intestinal wall.

• The "good" bacteria lactobacilli and bifidobacteria produce lactic acid. This lowers the pH value in the intestine and creates an acidic, gut-friendly environment. Foreign microorganisms do not feel comfortable in it and are restricted in their growth.

• Training for the immune system: Our gut bacteria stimulate our immune system around the clock and keep it busy. This is how the immune system is trained to distinguish between self and non-self. If our immune system were not capable of this, our defense would attack our own substances or see normally harmless food components as enemies. Allergies and autoimmune diseases would then have a free rein.

These three barriers of the intestine (gut-associated immune system, intestinal mucosa, and intestinal flora) form the largest defense center of our body and determine the strength of the immune response. It is therefore obvious to strengthen the body's defenses "from the gut".

Strengthening the immune system from the gut: That's what matters

To support the body's own defense system, it is important to maintain the balance of the intestinal flora and strengthen the intestinal barriers. However, our current lifestyle (processed foods, high stress, unbalanced diet) does not exactly promote the growth of "good" bacteria. Therefore, it is even more important to feed them properly.

Plant-based foods:

Dietary fibers are the food source for our gut bacteria. These are indigestible components from our food that we cannot process in the stomach and small intestine, so they pass undigested into the colon. There, they ultimately serve as food for our bacteria. Since dietary fibers are found exclusively in plant-based foods, you are benefiting your gut bacteria by increasing the proportion of plant products in your diet.

At least 30 grams of fiber per day is recommended. Legumes, whole grain products, oatmeal, chicory, leeks, Jerusalem artichokes, salsify, and parsnips are particularly beneficial and rich in fiber.

Variety:

But it's not enough with just these. The basis of a gut-friendly diet lies in a varied and balanced diet as possible. Our gut flora consists of thousands of different strains of bacteria, each digesting something different. If the diet is very one-sided, we are providing our gut with the same nutrients all the time and not feeding all strains. Consequently, the diversity of bacteria in the gut decreases, which is so important for the immune system and our health. Therefore, focus on the variety of our (plant-based) foods and eat as varied as possible.

The golden rule is: To eat at least 25 different plant-based foods per week.

How to achieve this guideline and how to eat 25 foods in one day, you can read here.

Probiotic Foods:

One way to increase the proportion of good lactic acid bacteria is to consume them through food. Probiotic foods contain large amounts of live microorganisms, which can, for example, help with. Lactic acid fermentation Fermentation has been used for thousands of years to preserve food. Incorporate fermented products such as sauerkraut, tempeh, or kimchi, and fermented dairy products like yogurt and kefir regularly into your diet.