1 How can you strengthen your immune system?
2 What weakens the immune system?
3 How does the immune system work?
4 Summary: The most important immune boosters & immune killers

What is good for the immune system? We provide you with the most important tips on nutrition & lifestyle for a strong immune system: which foods strengthen your immune system, why you should go into the forest more often and what stress has to do with all this.

How can you strengthen your immune system?

A large part of our immune system is "made, not born".[1] In other words, your lifestyle has a much greater influence on your immune system than your genes. What you do every day determines how strong (or weak) your immune system is and how well (or poorly) your body can defend itself against pathogens. It's in your hands. And we'll show you what you can do every day to get your immune system going.

Immune booster #1: A balanced diet strengthens the immune system

Your immune system can only work optimally if it is supplied with the necessary fuel. Sounds logical, right? And it is. What may not be quite so clear is what this fuel for a strong immune system looks like and where you get it from. The solution lies in a varied diet. You can strengthen your immune system with the right nutrients and foods: you can find tips for edible immune boosters below.

Vitamins: The be-all and end-all for our immune system

The fact that vitamins are "healthy" is nothing new. Nevertheless, science is only gradually discovering why and how exactly they work. One thing is already clear: vitamins make a key contribution to a functioning immune system.

In connection with strong defenses, the following is usually mentioned vitamin C is usually mentioned. It supports the formation of white blood cells. As a result Vitamin C accelerates all defense reactions in the body.[2] Natural sources of vitamin C are citrus fruits, berries, red pepper or kiwi. But watch out! This immune vitamin is extremely sensitive to heat. Orange juice, which is often touted as being rich in vitamin C, is therefore only a reliable source if it is freshly squeezed and not pasteurized. The best way to enjoy the fruit mentioned above is raw. This preserves the vitamin C and many other valuable ingredients.

Another key vitamin for the immune system is vitamin A. It supports the formation of antibodies and has an antioxidant effect. This means that it protects our cells from damage, promotes regeneration and slows down ageing processes.[3] Vitamin A is found in broccoli, kale, dairy products and eggs, among other things. Important for absorption: It is a fat-soluble vitamin. This means that it can only be absorbed by the body if it is consumed in combination with fat. So prepare your broccoli and kale with a little oil to support vitamin A absorption.

Also fat-soluble, a powerful antioxidant and good for the immune system, is vitamin E. It strengthens the cell membrane and thus protects our cells from harmful intruders. It also has an anti-inflammatory effect. In food, vitamin E is mainly found in vegetable oils, nuts and seeds.[4] These foods are also naturally high in fat and therefore guarantee the optimal absorption of vitamin E.

Gradually the "sun vitamin" D3 is also gradually coming to the fore. Previously mostly mentioned in connection with strong bones, the importance of vitamin D for the immune system is increasingly being discovered. It supports the formation of immune cells (including monocytes; more on this under point 3), has an anti-inflammatory effect and is even said to help prevent cancer.[5] During the coronavirus pandemic, it also became increasingly known that vitamin D3 can greatly increase the body's resistance to respiratory infections.[6]

The most important source of the "sun vitamin" is - as the name suggests - sunlight.

More precisely, it is the UVB rays in sunlight that are converted into vitamin D3 in our skin.[7] In our latitudes, it is difficult (especially in the winter months) to get enough sunlight for an adequate supply of vitamin D3. Dietary supplements or foods fortified with vitamin D can help to compensate for this. compensate for this deficiency. Vitamin D is also fat-soluble. Vitamin D supplements should therefore always be taken with a meal or in the form of oil-based drops.[8] It is best to clarify the dosage and period of intake directly with your trusted doctor.

The least known so far are the vitamins of the B group. Eight different vitamins are grouped under this term and fulfill a variety of vital functions. In relation to the immune system, the B vitamins are primarily involved in the formation of red blood cells and antibodies. Like vitamins A and E, they also have an antioxidant and therefore cell-protecting effect.[9] B vitamins from plant sources can be found in green vegetables, bananas, yeast and tofu. Eggs, fish and meat also contain certain B vitamins. However, these vitamins are very sensitive to heat and are largely lost when these foods are cooked.

The vitamins mentioned play a special role in your immune system. However, all vitamins are important for maintaining your bodily functions and defenses. An adequate supply of all vitamins, minerals and trace elements is the basic prerequisite for your health and immunity.

  • Vitamin C

    Central functions in the immune system

    • Supports the formation of white blood cells 
    • Accelerates defense reactions in the body 

    Natural sources

    • Citrus fruits
    • Berries
    • Red pepper
    • Kiwi

    To note

    • sensitive to heat
  • Vitamin A

    Central functions in the immune system

    • Supports the formation of antibodies
    • antioxidant

    Natural sources

    • Broccoli
    • Kale
    • Dairy products
    • Eggs

    Please note

    • fat soluble
  • Vitamin E

    Central functions in the immune system

    • Protects the cell membrane 
    • anti-inflammatory 
    • antioxidant

    Natural sources

    • vegetable oils
    • nuts
    • seeds

    To note

    • fat soluble
  • Vitamin D3

    Central functions in the immune system

    • Supports the formation of immune cells 
    • anti-inflammatory 
    • prevents cancer 
    • strengthens the immune system against respiratory infections

    Natural sources

    • Sunlight (UVB rays)
    • Breast milk
    • Oily fish (e.g. eel, salmon, sardines)
    • offal
    • eggs

    To note

    • fat soluble
  • Vitamin B

    Central functions in the immune system

    • Formation of red blood cells 
    • Formation of antibodies 
    • antioxidant

    Natural sources

    • green vegetables
    • bananas
    • Yeast
    • Tofu
    • Potatoes
    • Eggs
    • Fish
    • Meat

    To note

    • sensitive to heat

Secondary plant substances - The power of plants for your immune system

Secondary plant substances are the natural miracle cure for a healthy plant-based strengthening of the immune system. These are primarily fragrances and colorants in plants that serve to attract beneficial insects and keep pests away. They are, so to speak, the natural defenses of the plant world, which also serve the human immune system.[10] Secondary plant substances are found in all plant foods, but especially in fruit and vegetables. "Eat the rainbow!" is the motto. Because the more colorful, the richer in immune-boosting substances. Deep green leafy vegetables such as spinach, bright yellow peppers or deep red tomatoes are great sources of these plant-based immune boosters. Again, the same applies here: ideally, eat them raw![11]

Healthy intestinal flora - good digestion, good immune system!

The tight connection between digestion, metabolism and the immune system has only become the focus of scientific research in recent years. However, it is now clear that our immune system and digestive tract are closely intertwined.[12] The microbiome plays a particularly important role in this. The human microbiome consists of several trillion microorganisms that live in and on our bodies.[13] The majority of these are located in our intestines and are often referred to as intestinal flora. And it is precisely this intestinal flora that plays a central role in our health and our immune system.[14] Like the immune system, the microbiome is also influenced by a variety of factors - first and foremost, of course, our diet. For a healthy gut flora - and a strong immune system - you should therefore pay attention to the following points in your diet:

  • Adequate fiber intake
    (at least 30 g/day; found in fruit, vegetables, pulses and wholegrain products)[15]
  • Regular consumption of fermented foods (probiotics)
    (e.g. yogurt, kefir, sauerkraut, miso,...)[16]
  • Integration of prebiotics as food for intestinal bacteria[17]
    (occur naturally in chicory, Jerusalem artichokes and black salsify, among others)

Energy balance, regularity & fasting - balance for a strong immune system

Our immune system works best when we consume enough energy, but not too much. An undersupply of energy leads to a weakening of the immune system. In turn, if we consume too many calories, it is overwhelmed and can no longer fight off pathogens as effectively. In the long term, we should therefore balanced energy balance in other words, we should consume roughly the same number of calories as we burn.[18]

Also regular eating and digestive breaks are good for our immune system. Regularity in our food intake ensures a constant supply of energy. Fasting, on the other hand, brings our digestion - the most energy-intensive process in our body - to a standstill. And when there is no need for digestion, this energy can be invested in other processes - for example in detoxifying the body and building up a strong immune system. For these reasons Intermittent fasting is often mentioned in connection with a strong immune system: it combines regular meals with daily fasting intervals of between 12 and 20 hours.[19][20]

Immune booster #2: Regular exercise for a healthy immune system  

Physical activity promotes blood circulation and the transportation of lymphatic fluid and therefore accelerates the Distribution of immune cells. This means that our immune system becomes faster and more effective when we exercise. Exercise also has an anti-inflammatory effect and takes some of the work off our immune system. However, these positive effects on the immune system do not last in the long term. This is why it is all the more important to exercise every day and to take regular breaks from sedentary activities. The ideal immune booster between 30 and 45 minutes of moderate physical exertion every daysuch as brisk walking or easy running is recommended.[21][22]

In addition to the physical component, regular exercise contributes to stress reduction and emotional balance which in turn is associated with a stronger immune system.[23][24]

Immune booster #3: Spending time in nature strengthens the immune system

In addition to nutrient-rich food, nature also provides our immune system with all kinds of useful things. On the one hand, there is the sunwhich we have already mentioned as the most important supplier of vitamin D3. However, it is not only the vitamin itself, which is obtained from the sun's rays, that supports our immune system. When UVB sunlight is converted into vitamin D3, a substance called cathelizidine is also produced, which counteracts inflammation in the body and therefore supports our immune system.

On the other hand, in nature there are secondary plant substances for breathing. In native forests, up to 2,000 of these fragrances can be measured, which have a proven immune-boosting and calming effect on humans.[25]

Immune booster #4: Healthy sleep rhythm & melatonin activate the immune system

During sleep, our body regenerates, repairs, heals and detoxifies. While many other bodily functions take a break, our immune system really gets going at night. Now it can do its important work undisturbed. An important partner in this is the so-called "sleep hormone" melatonin. It is produced in the brain as soon as it gets dark and prepares our body for the nightly rest phase. The most important functions of melatonin are

  • Reduction of energy consumption, body temperature & blood pressure
  • Activation of the immune system
  • Anti-inflammatory & antioxidant effect[26][27]

For a balanced melatonin production are a regular day-night rhythm and sufficient sleep are important.[28] Try to get up and go to bed at roughly the same time every day. You should also avoid electric light and caffeinated drinks, especially in the evening, so as not to upset your melatonin levels.[29][30]

Immune booster #5: Conscious relaxation & stress reduction - rest is where the (immune) strength lies!

Strength lies in rest! This is especially true for our immune system. Our immune system can only perform its full range of health-preserving activities in a state of relaxation. That's why, in addition to sufficient sleep, we also need periods of rest and active stress reduction during the day. As already mentioned, this can be achieved through gentle exercise. Meditation and breathing techniques can also help us to consciously relax and calm our body and mind. In a state of relaxation, we not only feel emotionally and mentally calmer, our central nervous system also switches from stress-related "fight or flight" to "rest & repair", which requires rest. This activates and strengthens our immune system.[31][32]

Our top 5 immune boosters summarized

So the winning combo is: a (micro)nutrient-rich diet, moderate exercise in a sunny forest, followed by conscious relaxation and restful sleep - and all of this every day if possible. This is what paradise for our immune system must look like. And it actually sounds like a pretty pleasant life overall ;)
Here are the most important immune boosters that you can integrate into your everyday life:

  • A balanced diet
    (rich in vitamins, phytochemicals, fiber, pro- & prebiotics; balanced energy balance, regular meals & digestive breaks) 
  • Regular exercise
    (30-45 minutes daily; moderate intensity (e.g. fast walking or easy running))
  • Time in nature
    (sunlight & forest) 
  • Healthy sleep & melatonin
    (regular day-night rhythm, avoid electric light & caffeine in the evening) 
  • Conscious relaxation & stress reduction
    (gentle movement, meditation, breathing exercises) 

What weakens the immune system?

As we have already established: A strong immune system depends to a large extent on a healthy lifestyle. The immune boosters mentioned so far are a good start to supporting your immune system with your daily habits. But the most important immune killers also deserve our attention. Here we explain what you should avoid for the sake of your immune system.

Immune killer #1: Too much sugar & an unbalanced diet inhibit the immune system

Excessive sugar consumption can have a negative impact on our immune system. Sugar "feeds" inflammations and pathogens, boosts the release of the stress hormone cortisol and is associated with obesity.[33] It also brings our intestinal flora out of balance.[34] As a result, sugar makes it more difficult for our immune system to do its important work. But don't worry: this is mainly about refined sugar, industrially produced sugar. This should a maximum of 10% of your daily energy requirement make up.[35] Caution is particularly advised with "hidden sugar" in ready-made products and junk food and sugary drinks. As a healthy person, you don't need to worry about the natural sugar in wholesome foods such as fruit, vegetables and wholegrains.

In addition to too much sugar, an unbalanced diet is also problematic for our natural defenses. If you do not provide your body with enough energy and nutrients, your immune system cannot function optimally. Any deficiency symptoms are often only recognized when severe symptoms occur. We therefore recommend that you have a comprehensive blood count done regularly. This will allow you to keep track of your supply of vitamins, minerals and trace elements.

Immune killer #2: Chronic stress deactivates our defenses

Stress is probably the biggest enemy of our immune system. Among other things, this has evolutionary reasonsStress was originally there to protect us from danger. And if you are running for your life, you don't need an immune defense at the moment. All the energy is used for "Fight or flight" (fight or flight) into arms and legs; other bodily functions such as digestion or the immune system are put on the back burner. A large number of hormones that are released in extreme situations ensure this rapid prioritization - above all the "stress hormone" cortisol.[36]

In a acute stress situationwhere life and death are at stake, this reaction makes sense. We can digest, regenerate and ward off illness just as well after we have escaped a momentary external attack. However, it becomes problematic when such stress becomes a permanent state especially because it usually no real, physical danger exists.[37]

Our brain cannot distinguish between mental and physical stress. As soon as the signal says: "Imminent danger!", the same reaction occurs in our body - regardless of whether we are being shouted at by our boss or chased by a sabre-toothed tiger. The energy released by the perceived threat stress hormones have to be intensive exerciseThe stressors, such as the fight or flight for which they prepare us, must be reduced. If this does not happen, they remain in our body and cause chronic stress. This means that our immune defenses are permanently lowered. We become susceptible to infections of all kinds and fall ill more often.[38]

This is why a strong immune system is important: Stress as far as possible avoid and regularly train both physically and mentally reduce.

Immune killer #3: Excessive alcohol consumption & smoking damages the immune system

Excessive alcohol consumption has a negative effect on our intestinal flora and digestion, which are closely linked to the immune system.[39] Alcohol also promotes inflammation and inhibits the production of our prized monocytes.[40] Remember: these are the white blood cells from which our spleen produces macrophages (= scavenger cells). These macrophages play a central role in the body's defense against pathogens. Alcohol therefore has a weakening effect on our immune system for several reasons and is even associated with an increased risk of cancer.[41]

The harmful effects of smoking and nicotine are now also widely known. With regard to the immune system, the following effects are the most striking:

  • Development of inflammation
    Nicotine causes inflammation in the body because it activates certain white blood cells, which release pro-inflammatory molecules as a defense reaction.[42]
  • Increased susceptibility to infections (especially of the respiratory tract)
    Regular smoking impairs the quantity and quality of our immune cells. As a result, infections, especially in the respiratory tract, become more frequent and more intense.[43]
  • Formation of cancer cells
    Cigarette smoke (both actively and passively inhaled) is associated with a variety of cancers. It promotes the formation of cancer cells and at the same time weakens the natural defense mechanisms against harmful cells.[44]

How does the immune system work?

You now know how to strengthen your immune system in everyday life. But what is the immune system? If you explain the immune system in simple terms, it is usually referred to as the "army of defenses", that protects our body against diseases and infections.

Functions of the immune system

The most important immune system functions are

  • Pathogens (e.g. viruses, parasites & fungi) and remove them from the body
  • environmental toxins (such as heavy metals, exhaust fumes or ionizing radiation) and neutralize them 
  • pathological changes (such as the growth of cancer cells) and contain them[45]

In reality, of course, it is much more complex: our immune system is created by the sophisticated interaction between different organs, cell types and molecules. Each of them fulfills its own special function in our "defense army".

Tasks of the spleen: small organ, great importance for the immune system

An otherwise rather inconspicuous organ plays a special role in our immune system: the spleen. The organ, which is approx. 11 cm wide and 7 cm long, is located below the diaphragm in the left upper abdomen. The spleen fulfills three central functions, all of which are related to our immune system:

  • Production of lymphocytes
    Lymphocytes are a special type of white blood cell that fend off pathogens.[46]
  • Storage of monocytes and formation of macrophages
    Macrophages are so-called scavenger cells which, according to their name, absorb and dispose of harmful microorganisms (e.g. bacteria or tumor cells) in our body. Incidentally, macrophages are formed from monocytes - and this is where the aforementioned vitamin D3 comes into play again. The sun vitamin is extremely important for the formation of monocytes in the bone marrow, which then serve as the basis for the protective macrophages.[47]
  • Blood purification
    The spleen eliminates outdated and dysfunctional red blood cells, breaks them down into fragments and ensures that they are removed from the blood.[48]

Summary: The most important immune boosters & immune killers

FAQ - The most important facts about the immune system

What is the immune system?

"Immune system" is an umbrella term for various organs, cells and molecules in our body that work together to keep us healthy and protect us from disease. The white blood cells and the spleen play a special role.

Why do we need the immune system?

The main tasks of the immune system are

  • Pathogens harmless and remove them from the body
  • environmental toxins identify and neutralize
  • pathological changes to recognize and contain[49]

How do you strengthen your immune system?

The most important component for a strong immune system is a healthy lifestyle. This includes:

  • a balanced diet
  • regular exercise
  • Spending time in nature
  • a healthy sleep rhythm
  • conscious relaxation & stress reduction

What weakens our immune system?

The most widespread immune killers are:

  • chronic stress
  • too much sugar
  • unbalanced diet
  • excessive alcohol consumption
  • smoking

What happens when the immune system is weak?

If our immune system is weakened, we become susceptible to illnesses and infections. As a result, we fall ill more often, the symptoms of illness become more intense and last longer.

Collapsible content


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