What are probiotics?

You've probably heard that probiotic yogurts are healthy. But how exactly are yogurts supposed to promote health? What is meant by a "probiotic effect" and how is that related to the bacteria in yogurt? These questions are answered below.

What are probiotics?

Probiotics are living microorganisms (bacteria) that provide health benefits for humans. Probiotic foods have a particularly positive effect on the intestinal flora, i.e. the bacteria in the digestive tract (1).

Probiotics are crucial active ingredients that are necessary for the fermentation of food. This type of food processing has played an important role in the preservation of food for many centuries. Probiotics can not only preserve food, but also have a wide range of effects on the human body. One well-known probiotic product is yogurt. Its potential in promoting health and its role in the immune system played an important role as early as the beginning of the 20th century. A scientist named Elie Metchnikoff even received a Nobel Prize for his discoveries in the field of immune defense and was of the opinion that yogurt has health-promoting and life-prolonging effects.

Together with prebiotics, probiotics do not act directly on the human organism, but rather by influencing the intestinal flora. The term synbiotics is often used because the effects of probiotics and prebiotics complement each other synergistically (2). Prebiotics are not living microorganisms, but indigestible components of plant foods. They ferment in the large intestine and thus stimulate the growth of health-promoting bacteria (3). The effect of prebiotics can often be compared to classic dietary fiber. Dietary fiber is also indigestible, but differs from prebiotics in that it does not promote the specific proliferation of intestinal bacteria (2).

What types of probiotics are there?

There are numerous microorganisms with probiotic effects. The best known are bacteria of the genera Lactobacilli and Bifidobacteria. They produce lactic acid and are often referred to as "lactic acid bacteria". They are tolerant to stomach and bile acids, which means they can reach the large intestine alive and exert their effect there.

The Lactobacilli genus alone includes more than 100 different species of bacteria. However, they only make up a small proportion of approximately 0.01% of the intestinal flora. They can survive both anaerobically (without oxygen) and aerobically (with oxygen). Bifidobacteria include more than 50 different species. They are present in greater numbers than Lactobacilli and make up to 4% of the intestinal flora of adults. Bifidobacteria can only survive in environments without oxygen. Akkermansia muciniphila is one of the less studied bacterial species. This species is particularly important for an intact intestinal mucosa. This prevents foreign substances from entering the bloodstream (4).

Sources of prebiotics (4)

genus	Bacterial species
Lactobacilli (L)	L. casei, L. grasseri, L. planatrum, L. reuteri
Bifidobacteria (B)	B. breve, B. longum, B. bifidum, B. adolescentis
Yeast fungi	Saccharomyces boulardi, S. cereviciae
Other types of bacteria	Streptococcus thermophilus, Lactococcus lactis, Bacillus clausii

What sources of probiotics are there in food?

Probiotics are mainly found in dairy products such as yoghurt, butter, cheese and curd (2). Fermentation gives foods a unique taste and texture. Bacteria from the genera Lactobacilli are often used to produce fermented milk, meat and vegetable products. , streptococci, pediococci and leuconostoc. Acetic acid bacteria are involved in the fermentation of cocoa beans, vinegar and kombucha. Yeast fungi are involved in the production of beer, wine and bread. Different types of bacteria are often combined to produce a desired end product.

However, different production processes of certain foods can affect their probiotic effect. Sourdough, which is used to make bread, is also produced through fermentation. However, probiotic microorganisms are destroyed by the heat during baking. The same applies to wine and beer. The microorganisms used to produce them are either inactivated or no longer present in the final product (1).

What types of probiotics can you take as a dietary supplement?

Probiotics are also available in the form of dietary supplements. Examples of probiotics that can be taken as supplements are Streptococcus thermophilus, B. breve, B. longum, L. plantarum, L. acidophilus and L. paracasei (5).

Supplements exist either in capsule or powder form or can be added as probiotic supplements to the milk matrix during the manufacturing process. These are not microorganisms that are naturally present in the milk product, but rather selected types of probiotics. Dietary supplements offer the advantage that the type and amount of bacteria contained can be better controlled than in food (6).

What is the importance of probiotics in nutrition?

Probiotics are an important part of a balanced diet. Due to their ability to promote the growth of healthy bacteria and inhibit harmful bacteria, they support healthy intestinal flora and digestion. This has a positive effect on gastrointestinal complaints such as constipation, irritable bowel syndrome, diarrhea, stomach pain and flatulence. A healthy intestinal flora is also important for general health as it is linked to the immune system. So if good bacteria predominate in the intestine, they contribute to a stronger immune system (2).

Conclusion

Probiotics are live microorganisms that provide health benefits, particularly by promoting healthy intestinal flora. They are mainly found in fermented dairy products such as yogurt, cheese and cottage cheese, but can also be taken as a dietary supplement. Well-known probiotic bacteria include lactobacilli and bifidobacteria. These microorganisms survive passage through the gastrointestinal tract and exert their effects in the large intestine. A balanced diet that includes probiotics therefore supports digestion and general well-being by promoting the growth of healthy bacteria and inhibiting harmful bacteria.

Sources

1. Kok CR, Hutkins R. Yogurt and other fermented foods as sources of health-promoting bacteria. Nutr Rev 2018; 76(Suppl 1):4–15. doi: 10.1093/nutrit/nuy056.
2. Matissek R, Hahn A. Food chemistry. 10th, revised and updated edition. Berlin, Heidelberg: Springer Spektrum; 2023.
3. Biesalski HK, Grimm P, Nowitzki-Grimm S. Pocket Atlas of Nutrition. 8th, completely revised edition. Stuttgart, New York: Georg Thieme Verlag; 2020.
4. Pugliese S. Probiotics and prebiotics – power food for the intestines: With delicious recipes. Munich: Riva; 2018. Available at: https://ebookcentral.proquest.com/lib/kxp/detail.action?docID=5820187.
5. Schneider E, Doll JPK, Schweinfurth N, Kettelhack C, Schaub AC, Yamanbaeva G et al. Effect of short-term, high-dose probiotic supplementation on cognition, related brain functions and BDNF in patients with depression: a secondary analysis of a randomized controlled trial. J Psychiatry Neurosci 2023; 48(1):E23-E33. doi: 10.1503/jpn.220117.
6. Companys J, Pla-Pagà L, Calderón-Pérez L, Llauradó E, Solà R, Pedret A et al. Fermented Dairy Products, Probiotic Supplementation, and Cardiometabolic Diseases: A Systematic Review and Meta-analysis. Adv Nutr 2020; 11(4):834–63. Available at: https://www.sciencedirect.com/science/article/pii/s2161831322003131.