The topic of probiotics has really taken off in the last decades, and the evidence backing up the connection between our gut health and our overall well-being is piling up. To dive a bit deeper into this topic, I invited the incredibly talented researcher Deni Kostelac, PhD, to Stela’s Food Stories so that he can introduce us to the world of probiotics and how to get the best of them to improve our quality of life.
Q: Hello, Deni, and welcome to Stela’s Food Stories. Thank you for being with us. To start with, tell us a little something about yourself.
A: I graduated with a degree in Molecular Biotechnology from the Faculty of Food Technology and Biotechnology of the University of Zagreb, and after that, I obtained a doctorate in the field of probiotics from the same faculty. I am currently employed at the mentioned institution as a research associate in the Laboratory for General Microbiology and Food Microbiology.
For several years, I have been intensively engaged in researching probiotics, discovering new probiotic sources and developing new products based on probiotic bacteria. In my scientific research, I am focused on the development of a new, targeted approach to probiotic characterization, the introduction and application of biomedical methods in the research of probiotics, and the development of new systems for the release of probiotic bacteria in the human body.
Q: First things first: what are probiotics? Which are the most common species of bacteria used in probiotic products?
A: The primary definition of probiotics adopted by FAO (Food and Agriculture Organization) and WHO (World Health Organization) defines them as live microorganisms that, when applied, have a beneficial effect on the host. However, recent research has proven that the beneficial effects do not necessarily come from living microorganisms but can also be obtained from inactivated (dead) cells, their parts or the biological compounds that they produce.
The most commonly used probiotics are bacteria of the genera Bifidobacterium and Lactobacillus.
Q: What happens in our bodies when we consume a probiotic?
A: After consumption, probiotics pass to the lower part of the gastrointestinal system and interact with our intestinal microbiota. Probiotics have the ability to adhere (stay with our microbiota) and prevent the binding of dangerous pathogenic bacteria, balance the composition of our microbiota and produce molecules that send positive signals to our immune system.
“What we know for sure is that lifestyle, diseases, antibiotics and drugs certainly affect the microbiota”
Q: You have just mentioned the term intestinal microbiota. Could you explain to us what exactly that is?
A: The term intestinal microbiota refers to the entire population of microorganisms that colonize a certain place in the digestive tract. The total number of bacterial cells in the intestines is ten times greater than the total number of all cells in the body, which indicates the importance of the microbiota and our dependence on its proper functioning. Given the important role of microorganisms that make up the microbiota, it was often considered a separate organ. It is also important to understand the term microbiome -that is, a set of all the genes of the microbiota- but these terms are often used as synonyms, especially in less specialized literature.
Q: What is the purpose of the microbiota in our body? What affects its composition, and how does an unbalanced microbiota affect our health?
A: The microbiota is extremely important for the proper functioning of the immune system, as well as other human systems. It is known that the colonization of the intestine begins at birth, and its composition changes significantly during breastfeeding, feeding and growth.
Many studies are being conducted in the field of microbiota composition, and the results clearly show large differences between individuals. That is why it is still very difficult to say that one microbiota is good (healthy) and the other is not.
What we know for sure is that lifestyle, diseases, antibiotics and drugs certainly affect the microbiota. So, if there is a sudden undesirable change in the composition of the microbiota caused by some of the above-mentioned factors, we are talking about a disturbance in its balance, which as a result, can have a negative impact on the functioning of the immune system, and the ability to “fight” pathogenic bacteria, which can cause diarrhoea, constipation and many other negative effects.
“We cannot claim with certainty that fermented foods are automatically rich in probiotics.”
Q: Which foods are naturally rich in probiotics?
A: Many foods contain a large number of microorganisms. The simplest examples are, say, fermented dairy products or fermented cabbage. However, it is very important to note that the probiotic classification for each individual microorganism is tested by a series of strict criteria and confirmed by clinical studies. Therefore, we cannot claim with certainty that fermented foods are automatically rich in probiotics. For this reason, we can also notice the difference between “ordinary yoghurt” and yoghurt with the addition of probiotic bacteria on the store’s shelves.
Q: What are the health benefits associated with the consumption of probiotics?
A: Decades of research on a great number of discovered probiotic microorganisms have shown numerous beneficial effects on the host’s health. Namely, our immune system is in constant interaction with the intestinal microbiota. This is an extremely complex relationship with a significant impact on the entire organism.
Lifestyle, diet, medications and everything else that we introduce into the body affects the composition and functioning of the intestinal microbiota, and due to the interconnectedness of the body, this affects other systems such as the cardiovascular, nervous and respiratory systems, as well as the skin, among others. Since probiotics also affect the composition and functioning of the microbiota, it is logical and proven in numerous studies that probiotics also affect all these systems.
I would cite just a few examples where studies have shown the beneficial effects of probiotics on neurodegenerative diseases, diabetes, irritable bowel syndrome, allergic reactions, SARS-CoV-2 infections, autoimmune diseases and many other conditions.
Q: What has proven to be more effective, foods rich in probiotics or probiotic food supplements? Are they compatible?
A: The number of probiotic microorganisms and the needs of the user should be taken into account here. Namely, in order to successfully manifest the beneficial effects of an individual probiotic, it is necessary to consume them in sufficient quantity at the target location (most often in the intestines). What is most effective on the market are commercially available probiotics classified (and regulated) as drugs or pharmaceutical products and backed by clinical studies that prove their beneficial effects on health.
On the other hand, it is difficult to directly compare the effectiveness of nutritional supplements, of which there are many on the market, and they are extremely variable in composition.
That is to say, it is important to emphasize that nutritional supplements are not intended for the treatment of diseases but nonetheless, they provide benefits for our health. Hence, they are not subject to the mandatory procedure of obtaining approval from HALMED (Agency for Medicinal Products and Medical Devices of Croatia), nor are their side effects monitored as it is done with medicines. Furthermore, dietary supplements are not regulated by drug legislation but by food legislation.
The end user should definitely take care and research which probiotic is in the product, whether it has proven beneficial effects and how many probiotic cells are in one dose.
Although there are certain disagreements, it can be found in the scientific literature that the minimum, i.e. the lower limit of the number of probiotic cells necessary for the health effects to manifest is around 10^6-10^8 CFU/g (colony-forming unit/ g), while in most products the average is declared around 10^9-10^11 CFU/g.
“As part of my doctoral thesis, I developed a three-layered probiotic capsule that releases probiotics in a targeted manner, layer by layer, in the mouth, stomach and intestines.”
Q: Can you give us some pointers? How often should they be taken, how long for and how long does the effect last?
A: Unfortunately, no scientific consensus has yet been reached regarding the recommended intake periods. On the other hand, if the need to take probiotics is determined for an individual, the course of intake will be defined in agreement with the doctor.
Q: As consumers, how much should we trust the labels of probiotic products on the market?
A: There are some worrying facts about probiotics: several scientific studies have found the inadequacy of a significant number of commercially available probiotics in Europe and the US. It has been shown that the products are not of adequate quality, do not contain the specified cultures in the concentrations indicated on the packaging, and sometimes contain microbial contaminants. Also, the authors of the research claim that on the market of probiotic products, even in developed countries, the beneficial effects of their consumption are often misrepresented. To date, no studies have been published that show such data for the entire Croatian market.
Q: Even if the composition of the product matches what the label says, are there any external factors that can affect its composition, such as time or storage conditions?
A: Some of the challenges of developing foods enriched with probiotics are the stability of probiotics in different environments, the shelf life and the precision of delivering them in sufficient concentration to the target site in the gastrointestinal system.
Of course, since we are mostly talking about living cells of microorganisms, they are sensitive to changes in environmental parameters. When developing a product, it is necessary to test the stability over time and the storage conditions and clearly state on the packaging how to store the product before and during application to ensure that the cells are active and in sufficient numbers to be able to deliver beneficial effects.
Q: That was a lot of insightful information, and I can see that there is still much more to discover and understand about probiotics. What is keeping you busy nowadays? Can you tell us a bit about what you are currently working on?
A: As part of my doctoral thesis, I developed a three-layered probiotic capsule that releases probiotics in a targeted manner, layer by layer, in the mouth, stomach and intestines. The idea came during my research, where I found and investigated probiotics that act against the bacteria that cause caries and periodontitis in the mouth, inhibit Helicobacter in the stomach and have anti-inflammatory and antioxidant effects in the intestines.
For this capsule, I was awarded a gold medal at the International Innovation Exhibition (ARCA 2021) and a special award for the health significance of the innovation at the Bjelovar Innovation Show.
I am now continuing research in the mentioned areas in order to investigate in more detail the mechanisms of action of new probiotics, especially those that I found in donkey milk, which is traditionally used for its beneficial health effects.
Additionally, I am also investigating the potential of newly discovered inactivated (dead) probiotic cells, which I have proven to protect DNA from oxidative stress and have an anti-inflammatory effect too.
I also participate in several projects where we consider the potential of probiotics in aquaculture in order to reduce the harmful effects of climate change, and I’m also a collaborator on a project that is developing 3D printed fruit juices with the addition of probiotics using green, sustainable technologies.
Q: Those are all outstanding achievements, and I really look forward to seeing where your research leads to. Before we finish, I would really like to hear your thoughts on the future of probiotics. What can we expect to see in the coming years?
A: I see the future of probiotics in personalized applications where probiotics will be created for each individual. I believe that further research will reveal complex mechanisms of action, and bacteria with probiotic properties will be found more quickly and precisely.
Also, a better understanding of the microbiome and the development of technology will enable automated analysis and probiotic characterization, and one day, probiotics designed just for each individual will be available. For example, if a person takes a certain antibiotic, it will be easy and convenient to detect the imbalance of the microbiota and precisely and quickly develop a probiotic product designed to restore balance for that person. Of course, there is a lot of research and development of technology ahead of us in order to achieve that.
Photo by Marija Gašparović
