The best friends of your immune system

What are probiotics?

Probiotics are living microorganisms that can potentially provide health benefits when consumed in sufficient amounts. They help stabilise the microbial balance in the gut. This complex ecosystem of billions of bacteria is located primarily in the large intestine, but also in the small intestine.

Probiotics are not a homogeneous group; they consist of various bacterial strains with sometimes very different properties. Well known are members of the genera Lactobacillus and Bifidobacterium, which also occur naturally in the human digestive tract. They are found, for example, in fermented foods such as yoghurt, kefir or sauerkraut, but also in probiotic dietary supplements or medicinal products.

For a microorganism to be considered a probiotic, it must meet certain criteria: it must survive the passage through the gastrointestinal tract, be able to reproduce in the gut, have demonstrable health‑promoting properties, display stable genetic characteristics and be able to produce substances that inhibit the growth of harmful microbes.

Already at birth the foundations of an individual's gut flora are laid. Newborns acquire their first probiotic microbes during birth or later via breast milk. These support the establishment of a healthy gut colonisation. Early microbes therefore make an important contribution to the development of the immune system and to colonising the gut with beneficial bacteria.

How do probiotics work in the body?

Probiotics exert their effects on several interconnected levels. A prerequisite is that they pass through the gastrointestinal tract intact and reach the large intestine in active form. There they exert targeted influence on the microbial balance.

Initially, probiotics promote the settlement of beneficial gut bacteria and simultaneously inhibit harmful microbes by worsening their living conditions. By producing organic acids, they lower the pH in the gut and create an environment that makes it harder for pathogenic microorganisms to grow. Additionally, they produce antimicrobial substances that are directed against unwanted pathogens. Probiotics also support the protective function of the intestinal mucosa. An intact barrier prevents harmful substances or undigested food components from entering the bloodstream and triggering inflammatory processes. This barrier function plays an important role in chronic inflammation and intolerances.

Another central effect concerns the immune system, most of which is located in the gut. Probiotics act in a regulatory manner by activating specific immune cells while damping excessive defence reactions. This strengthens the immune response without causing overstimulation. Probiotics also bring many benefits for digestion: they aid the breakdown of hard‑to‑digest food components, stimulate the body's vitamin production (e.g. B12, folic acid, vitamin K) and provide energy to gut cells via short‑chain fatty acids. They also support healthy intestinal motility.

An especially interesting area is the connection between the gut and the brain. Through the so‑called gut‑brain axis, probiotic bacteria influence the central nervous system. By participating in the production of neurotransmitters such as serotonin, they can positively affect emotional balance and alleviate stress‑related symptoms. Individual strains have even been associated with improved mood and reduced anxiety.

Last but not least, probiotics can also improve skin condition and metabolism. By stabilising the microbiome, optimising digestion and regulating hunger, they have anti‑inflammatory effects — which can also positively affect skin and weight.

Do probiotics help with irritable bowel syndrome?

Numerous scientific studies and medical guidelines indicate that certain probiotics can contribute to the relief of irritable bowel syndrome (IBS). The goal of treatment is not only to reduce troubling symptoms such as bloating, abdominal pain or irregular stools, but also to strengthen the intestinal barrier and regulate inflammatory processes in the digestive tract.

Particular emphasis is placed on so‑called multispecies preparations, i.e. combinations of different probiotic bacterial strains. These have often proven more effective than single strains in studies. Depending on the symptom pattern, different bacterial cultures can be used to target pain relief, relieve constipation or normalise bowel activity in cases of diarrhoea.

The mucosal immune system, i.e. the immune system of the intestinal mucosa, is also the subject of current research. Certain probiotic mixtures appear to strengthen it by promoting the production of anti‑inflammatory substances and by dampening stress‑related irritations. Positive side effects, such as a balanced production of serotonin and melatonin, can also improve overall wellbeing.

Probiotics and prebiotics: what is the difference?

Probiotics and prebiotics fulfil different yet complementary functions with regard to gut health. Probiotics are living microorganisms intended to colonise the gut with health‑promoting bacteria. Prebiotics, by contrast, are specific indigestible fibres that serve as food for these beneficial bacteria.

Probiotic microorganisms such as lactobacilli or bifidobacteria are found in fermented foods or specialised supplements. They are intended to settle in the gut and positively influence the microbiome. Prebiotics such as inulin or oligosaccharides, on the other hand, pass undigested into the large intestine and promote the growth of beneficial microbes already present.

In short, probiotics provide the “good” bacteria and prebiotics their preferred energy source. Together — often combined as synbiotics — they can help strengthen the balance of the gut flora.

Do probiotics help against allergies?

Allergies are widespread, but classic therapies often show limited effectiveness. Research is therefore increasingly focusing on probiotics. Certain strains, such as Lactobacillus paracasei LP‑33, have produced promising results in studies. Especially for hay fever, regular intake has been associated with a marked reduction in symptoms, both when taken alone and in combination with the antihistamine loratadine.

The positive effect is partly attributed to the influence of probiotic microorganisms on the immune system. These can attenuate excessive reactions to harmless environmental substances and thus alleviate symptoms such as rhinitis or skin irritations. Experts recommend starting an appropriate preparation about a week before the pollen season begins. The use of certain probiotics is also increasingly being considered as a supportive measure during pregnancy and breastfeeding.

Probiotics for bad breath: effective or not?

Probiotics are increasingly considered a potential adjunct in the treatment of bad breath, particularly due to their effect on the oral microbiota. Studies show that certain strains such as Lactobacillus reuteri, L. salivarius, Streptococcus salivarius or Weissella cibaria can help reduce the concentration of sulphur‑containing compounds responsible for unpleasant breath odour in the short term. This effect appears to be based on a change in the microbial balance in the mouth.

However, the benefit remains limited so far. While breath odour was measurably reduced in several studies, a lasting solution to the main causes such as tongue coating or plaque was not achieved. The current evidence is therefore not yet sufficient to recommend probiotics as a standalone measure for halitosis. They may, however, be considered as a complementary approach, particularly after professional dental cleaning and with consistent oral hygiene.

How you can benefit from probiotics: effective tips

• When buying probiotic foods, make sure they have not been pasteurised, since heating kills the microorganisms they contain. Choose, for example, lacto‑fermented sauerkraut from a health food store rather than jarred sauerkraut from the supermarket.
• Include fermented products such as kimchi, miso or tempeh in your diet to benefit from the probiotic cultures they contain. You can also draw on international recipes.
• A healthy alternative to soft drinks are probiotic beverages such as kombucha, water kefir, kefir, kvass or organic plain yoghurt.
• Ideally take probiotics in the morning on an empty stomach with lukewarm water to speed gastric transit and increase the survival rate of the bacteria.
• If you are taking antibiotics at the same time, take probiotics with a gap of two to three hours to avoid impairing their effect.
• If you are lactose intolerant, use lactose‑free yoghurt or fermented plant‑based alternatives such as soy or coconut yoghurt, as these also contain lactic acid bacteria.
• Also supplement your diet with prebiotic fibres such as pectin, inulin or beta‑glucans to improve the living conditions of probiotics in the gut. Good sources include apples, oat bran or Jerusalem artichoke.
• Buy probiotic cheese products such as unpasteurised alpine cheese or Parmesan, because the number of lactic acid bacteria increases during prolonged ageing.
• In case of chronic disease or weakened immune defence, consult a doctor before taking probiotics, as in rare cases bacterial translocation with systemic infections can occur.
• Use probiotics specifically to regenerate your gut flora after an antibiotic therapy, ideally over a period of several weeks. This can reduce the risk of antibiotic‑associated diarrhoea.
• If you cannot tolerate fermented products, you can instead use probiotic lozenges or drops. These are often easier to digest and allow more targeted dosing.
• Always follow the manufacturer's consumption recommendations. Excessive dosages can, in particular with reduced gut motility or when taking acid‑blocking medication, lead to side effects.

Probiotics are a natural way to help keep the body in balance. Their positive effects are most evident with regular use and a healthy lifestyle.