Probiotics: Advanced Food and Health Applications

Probiotics: Advanced Food and Health Applications presents the functional properties and advanced technological aspects of probiotics for food formulation, nutrition, and health implications. Specifically, the book addresses the fundamentals of probiotics, from their discovery to actual developments, the microbiological aspects of the main genus showing probiotic properties, the natural occurrence of probiotic strains in foods, the development of nutraceuticals based on probiotics, and the relationship of probiotics to health. The book also includes a discussion on regulatory aspects. 

This book is an excellent resource for food scientists, nutritionists, dieticians, pharmaceutical scientists, and others working with probiotics or studying related fields. 

• Introduces basic concepts on probiotics and describes the properties of main microorganisms with applications in probiotics
• Provides a description on the natural presence of probiotics in different food matrixes and how probiotics can be developed for incorporation in food formulations
• Offers advice on how probiotics can be used as nutritional input, along with their value on the preservation of healthy intestinal status, and their potential benefits in specific illnesses
• Contains definitions, applications, literature reviews and recent developments
• Includes a general introduction to the subject, taxonomy, biology, primary sources of probiotics and development of probiotics as food ingredients, human nutrition and health properties, and the use of high-throughput technologies in probiotics characterization

• Language: English
• Publisher: Academic Press
• Release date: Dec 2, 2021
• ISBN: 9780323903554

Book preview

Chapter 1: An introduction to probiotics

Priscilla Magro Reque; Adriano Brandelli    Department of Food Science, Institute of Food Science and Technology, Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, Brazil

Abstract

Probiotics are microorganisms capable to promote health benefits to the host. This chapter presents an introduction to the history of fermented foods and probiotics, as well as the probiotics concept and beneficial properties to human health, relationship with the human intestinal microbiome, global market, food safety and regulatory issues and main existing challenges in the field. For this, a historical contextualization and concept evolution of probiotics and related terms, up to the present day, is presented. Afterward, the necessary criteria for the selection and approval of probiotic microorganisms by the regulatory agencies are discussed, as well as regulatory issues and main obstacles encountered. In addition, beneficial health properties and potential therapeutic uses of probiotics in several diseases have been briefly addressed.

Keywords

Probiotics; Human gut microbiome; Health promotion; Gut dysbiosis and diseases; Food microbiology

1.1: Introduction

The intestinal luminal surface contains billions of live microorganisms, most of them located in the colon. Therefore, the human intestine can be considered an essential ecosystem for efficient absorption of nutrients and health maintenance in general (Olveira & González-Molero, 2016). Some live microorganisms are able to improve host’s health, when administered at a certain amount, and are called probiotics (Hill et al., 2014). According to Nowak and collaborators, probiotic microorganisms can act preventing the development of harmful microorganisms through the production of antimicrobial substances, enhancing cellular immune response by the activation of macrophages and natural killer cells, and the release of cytokines, or improving the gastrointestinal immune system by increasing the content of IgA(+) cells (Nowak, Paliwoda, & Błasiak, 2019).

The probiotic term is derived from the Latin word pro and the Greek word bios, which means for life (Pradhan, Mallappa, & Grover, 2020). Fermented products like beer, bread, wine, kefir, and cheese were used very often for nutritional and therapeutic purposes long before today’s knowledge about the health benefits of probiotic microorganisms (Ozen & Dinleyici, 2015). Probiotic food industry has been considered the future of functional food market, as economic data expect an increase from US$ 3.3 billion to US$ 7 billion for the global probiotic food supplement market from 2015 to 2025. Also, consumers are becoming more aware and have been looking for foods that, in addition to the function of nourishing, add health benefits, thus guiding industries to emphasize functional foods promotion (Khedkar, Carraresi, & Bröring, 2017).

Currently, the global market for probiotic products yielded US$ 48.4 billion in 2019 and is in expansion, presenting a predicted compound annual growth rate (CAGR) of 7.4% for the period from 2019 to 2024 (BBC, 2020). Asia is considered the largest probiotic market and has also a high growth rate (Mordor Intelligence, 2019). This expansion can be related to the considerable increase in the population’s interest about health and lifestyle issues, in addition to the probiotics use for preventing and/or treating metabolic and digestive disorders (Elshaghabee et al., 2017). Global probiotics market has already been consolidated, with well-known companies constantly working on the development and commercialization of novel products with probiotic claims (Global Market Insights, 2019).

Although dairy products are the most popular form of probiotic consumption, there are other foods containing probiotics that are available to the consumer, such as fruit juices and chocolates, although these still represent only a small part of the probiotic foods market (De Prisco & Mauriello, 2016). However, there is a significant increase in consumer’s demand for nondairy probiotic products, especially those that are low in lactose and cholesterol and do not need to be refrigerated. Some of the main innovations in such probiotic market niche are juices, nondairy drinks (like Kombucha), cereals, and chocolate-based products (Mordor Intelligence, 2019). There is excellent market potential in other vegetarian probiotic products development. In this sense, an interesting field to be explored can be the identification of new probiotic microorganisms for the fermentation of vegetarian foods, such as strains with specific probiotic properties, like vitamin B12 production (Kwak, 2014). Therefore, in this chapter, some general concepts and history on the field of probiotics will be presented, as well as the prospective nutritional and health benefits associated with their consumption and safety and regulatory challenges.

1.2: Probiotics: Historical context and concept evolution

Lactic acid fermentation of plant foods is believed to have been used since about 1.5 million years ago. This was a common practice in Europe until the industrial revolution and continues to be used regularly by several African communities, as it is a simple form of food preservation. Thus, the hominid gastrointestinal tract (GIT) was gradually adapted to a high daily supply of live lactic acid bacteria. However, in the 20th century, these foods had their consumption reduced in industrialized countries, which may have caused several gastrointestinal and immunological problems (Olveira & González-Molero, 2016).

In ancient Egypt, fermented dairy products like Laban Rayad and Laban Khed, that are still common nowadays in the Middle East, have already been consumed as early as 3500 BCE and have been traced to almost 10,000 years ago by molecular archeology techniques. Information about milk fermentation is attributed to the Sumerians around 2000 BCE, with different cheese recipes, in addition to a poem about beer production, from approximately 3000 BCE (Ozen & Dinleyici, 2015). In the year 76 CE, the Roman historian Plinio has recommended fermented dairy products for gastroenteritis treatment (Olveira & González-Molero, 2016).

Lactic acid-producing bacteria were discovered by Pasteur in 1857 (Fig. 1.1). Scientists from the same institute isolated lactic acid bacteria (LAB) from the intestinal tract in the late 19th century (Ozen & Dinleyici, 2015). In the early 20th century, Elie Metchnikoff related the longevity of some populations located in the Balkans to a regular consumption of fermented dairy products containing lactobacilli (Zommiti, Feuilloley, & Connil, 2020). Metchnikoff postulated that lactic acid bacteria offered benefits to human health and promoted longevity, suggesting that many diseases were caused by the effect of toxins and metabolites produced by certain microorganisms. He also proposed that intestinal autointoxication and aging could be suppressed by modifying the intestinal microbiota and using beneficial microorganisms to replace proteolytic microbes (World Gastroenterology Organization, 2017), such as Clostridium, which are producers of toxic substances.

Fig. 1.1

Fig. 1.1 Milestones in the history of microbial probiotics. (Information compiled from Zommiti, M., Feuilloley, M. G. J. & Connil, N. (2020) Update of probiotics in human world: A nonstop source of benefactions till the end of time, Microorganisms. MDPI AG, p. 1907. https://doi.org/10.3390/microorganisms8121907. and Johnson, B. R. & Klaenhammer, T. R. (2014) Impact of genomics on the field of probiotic research: Historical perspectives to modern paradigms, Antonie Van Leeuwenhoek. Springer Science and Business Media LLC, 106(1), pp. 141–156. https://doi.org/10.1007/s10482-014-0171-y.)

Experimental data supporting Metchnikoff’s theory were provided in 1906 by Michel Cohendry, a scientist from Pasteur Institute. Cohendy observed that the bacterium Bulgarian bacillus (currently identified as Lactobacillus delbrueckii subsp. bulgaricus) was recoverable from feces in two feeding trials with human individuals. This bacterium was associated with reduced incidence of putrefactive toxins and helped in the treatment of colitis after transplantation to the large intestine. These studies on L. bulgaricus captivated health-conscious people in Europe in the early 20th century, and the Pasteur Institute of Paris rapidly began the commercialization of the Lactobacillus under the label of Le Ferment (Johnson & Klaenhammer, 2014). In addition, Henry Tissier had already hypothesized that the administration of a Bifidobacterium strain, isolated from a breastfed baby, could treat infant’s diarrhea caused by proteolytic bacteria in 1906 (World Gastroenterology Organization, 2017).

Despite the promising achievements made in the early 20th century at the dawn of the probiotic concept, solid scientific evidence suggesting any definitive probiotic strains or their supposed health-promoting mechanisms was still missing. In fact, the inability of L. bulgaricus to survive gastric transit and colonize the small intestine was described in a study of Leo Rettger and collaborators at Yale University. The study raised an important question about which strain(s) could be present in the original therapeutic administration studies performed by Cohendy and later commercialized as Le Ferment. Alternatively, Lactobacillus acidophilus showed the capability to survive gastric transit and modify the gut microbiota in conditions of lactose and dextrin supplementation, and it was therefore suggested as a more suitable candidate for therapeutic applications. However, due to methodological limitations for identifying Lactobacillus species at that time, it is unknown whether the cultures administered during those studies were indeed pure L. acidophilus, Lactobacillus gasseri, or mixed culture with L. acidophilus and other acid-tolerant lactobacilli (Johnson & Klaenhammer, 2014).

Later, the Japanese physician Minoru Shirota used a Lactobacillus casei strain called Shirota, isolated from human feces, to treat diarrheal outbreaks in Japan, and then, a probiotic product with such bacteria was developed and has been commercialized since 1935 under the label of Yakult (World Gastroenterology Organization, 2017). This was one of the first fermented milk products to deliver a pure and defined strain and represented a noticeable advancement for the profitable dairy industry. Yakult remains as a staple product in Japanese, Korean, Brazilian, Australian, and European markets.

According to Puebla-Barragan and Reid, the focus on beneficial microbes as distinct from pathogens was largely ignored from the 1960s until the early 2000s (Puebla-Barragan & Reid, 2019). Nonetheless, probiotics definition was initially proposed in 1965, which considered as probiotics the substances secreted by microorganisms that stimulated others growth, in contrast to antibiotics. In the 1980s, it was found that some diet indigestible components (prebiotics) could promote the growth of certain bacterial strains present in the intestine and associated with health benefits (Olveira & González-Molero, 2016). Currently, the concept of probiotics was established by the Food and Agricultural Organization of the United Nations and World Health Organization (FAO/WHO, 2001) and later revised by the International Scientific Association for Prebiotics and Probiotics (ISAPP), being defined as live microorganisms that, when administered in adequate amounts, confer a health benefit on the host (Hill et al., 2014).

ISAPP also defines the term prebiotic as a substrate that is selectively utilized by host microorganisms conferring a health benefit. Most studied prebiotics are the plant carbohydrates inulin, fructooligosaccharides (FOS), and milk oligosaccharides like galactooligosaccharides (GOS), and human milk oligosaccharides (HMOs). Although the prebiotics with the most well-documented health effects to date are fermentable carbohydrates, the consensus definition includes a broad range of substances targeting different host niches, such as mouth, skin, or urogenital tract (Gibson et al., 2017).

As prebiotics stimulate the probiotic effects, the concept of synbiotics was created to overcome the challenges imposed during gastrointestinal transit of probiotics, indicating that the association of prebiotics and probiotics reinforces their individual beneficial effects. The ingesting of properly selected probiotics and prebiotics has synergistic beneficial effects and therefore suitable information on which prebiotics stimulate specific known probiotic strains would lead to the selection of ideal microorganism-substrate synbiotic sets. Thus, the identification of appropriate probiotic and probiotic pairs should be the main criteria for synbiotic formulation. The prebiotic should have a beneficial effect on health and selectively stimulate the growth of probiotic microorganisms, with no or limited stimulation of other microorganisms. The main probiotic species used in synbiotic formulations include Lactobacillus spp., Bifidobacteria spp., Saccharomyces boulardii, and Bacillus coagulans, while the most common prebiotics are FOS, GOS, and XOS (Markowiak & Ślizewska, 2017).

A recent ISAPP definition of synbiotic is reported as a mixture, comprising live microorganisms and substrate(s) selectively utilized by host microorganisms, that confers a health benefit on the host. The panel have also defined two distinct synbiotic types: a synergistic synbiotic, where the substrate is designed to be selectively utilized by the co-administered microorganism(s) and does not necessarily have to be individual probiotics or prebiotics, if the synbiotic itself is health-promoting, and a complementary synbiotic, that is an established probiotic combined with an established prebiotic designed to target autochthonous microorganisms (Swanson et al., 2020).

Although the health benefits of probiotics and prebiotics on modulating the gut microbiome have been recognized, some technological and functional limitations such as viability controls have hindered their full potential applications in food and pharmaceutical areas. Therefore, novel terms have arisen to define the abilities of nonviable probiotics- and/or probiotics-derived molecules. Nowadays, some terms are being used to define new concepts and biotherapeutic products containing probiotics (Martín & Langella, 2019), including some of the following definitions.

–Pharmabiotics: human microbial cells or their products that have a proven role in health or disease (like psychobiotics and immunobiotics);

–Postbiotics: nonviable microorganisms or their metabolic products that have some biological activity in the host;

–Paraprobiotics: nonviable microbial cells or crude cell extracts that provide some benefit to the consumer when administered in adequate amounts;

–Probioceuticals/probiotaceuticals: probiotic-derived substances (like reuterin from L. reuteri);

–Live biotherapeutic product (LBP): a product containing live organisms in order to prevent, treat, or cure a human condition or disease;

–Next-generation probiotic (NGP): live microorganisms identified by comparative microbiota analyses that provide some benefit to the host when administered in adequate amounts.

Although these terms have not been consistently used, the term postbiotics is often employed to define the complex mixture of metabolic products secreted by probiotics, including cell-free supernatants, enzymes, proteins/peptides, short-chain fatty acids, vitamins, biosurfactants, amino acids, peptides, organic acids, terpenoids, and phenolics. Otherwise, the term paraprobiotics corresponds to the inactivated microbial cells of probiotics (intact or ruptured cell components) or crude cell extracts with complex chemical composition. However, the term postbiotics has been used in many instances for the whole category of postbiotics and paraprobiotics (Nataraj et al., 2020).

Considering that these terms are increasingly found in the scientific literature and on commercial products, even lacking a clear definition and a consistent use, the ISAPP organized a panel of experts specializing in nutrition, microbial physiology, gastroenterology, pediatrics, food science, and microbiology to review the definition and scope of postbiotics. The panel recently defined a postbiotic as a preparation of inanimate microorganisms and/or their components that confers a health benefit on the host. Effective postbiotics must contain inactivated microbial cells or cell components, with or without metabolites, that contribute to observed health benefits. The panel also observed that other related terms, such as paraprobiotics, parapsychobiotics, ghost probiotics, metabiotics, tyndallized probiotics, and bacterial lysates have also been used, suggesting that the term postbiotic should be used always when applicable as the field would benefit from merging around the use of a single, well-defined term rather than the use of different terms for similar concepts (Salminen et al., 2021).

1.3: Selection criteria for probiotic microorganisms

It is widely recognized that the human digestive tract is sterile until the moment of birth; however, new studies suggest that colonization of the fetal intestinal microbiota may begin even in the uterus. In general, a healthy adult gastrointestinal tract is inhabited by a complex, dynamic, diverse, and interactive microbial community (Tesfaye et al., 2019). According to Kumar and co-workers, the human gastrointestinal tract has about 10 types of microorganisms and more than 5000 bacterial species, of which approximately 90% belong to the phyla Bacteroidetes and Firmicutes, and the others belonging to the phyla Actinobacteria, Proteobacteria, and Verrumicrobiota (Kumar et al., 2016). Bacteroidetes are Gram-negative, not spores forming, and anaerobic bacteria, while Firmicutes is composed mainly of Bacilli and Clostridia classes (Belizário & Faintuch, 2018).

Some authors describe that there are around 1000 different microorganism species per gram of human gastrointestinal lumen, and almost 99.9% of them are strict anaerobes (Tesfaye et al., 2019). Bifidobacteria and lactobacilli represent the main groups of normal intestinal microbiota in healthy humans (Pradhan et al., 2020). Numerous bacteria and yeasts strains have been characterized as potentially probiotic; however, members belonging to the genera Lactobacillus and Bifidobacterium constitute the main representatives, although other genera have also been commercialized as probiotics, such as Enterococcus, Streptococcus, and Saccharomyces (Sarao & Arora, 2017). Most known probiotics have been isolated from human gut microbiota and traditional fermented foods, being considered as Generally Recognized as Safe (GRAS), at the strain level by the United States Food and Drug Administration (FDA), or under the Qualified Presumption of Safety (QPS) criteria, at the species level by the European Food Safety Authority (EFSA) (Martín & Langella, 2019; Pradhan et al., 2020). In addition, the EFSA has granted status QPS for some species of Lactobacillus, based on their safety criteria (identity, possible pathogenicity, end use). To date, 37 species of Lactobacillus have received QPS status and include well-known species, such as L. acidophilus, L. amylolyticus, L. amylovorus, L. animalis, L. alimentarius, L. brevis, L. casei, L. delbrueckii, L. helveticus, L. pentosus, L. plantarum, L. paracasei, L. paraplantarum, L. reuteri, L. rhamnosus, and L. sakei (Koutsoumanis, 2020). The International Journal of Systematic and Evolutionary Microbiology (IJSEM) recently released a new classification on the species of the Lactobacillaceae family under Lactobacillus, Paralactobacillus, Pediococcus, and 23 novel genera, based on various genetic approaches and markers (Zheng et al., 2020). It is worth mentioning that some species formerly belonging to the genus Lactobacillus used as probiotics have been renamed as Lactiplantibacillus (e.g., L. plantarum), Lacticaseibacillus (e.g., L. casei), Limosilactibacillus (e.g., L. reuteri), Levilactobacillus (e.g., L. breve), and others.

Fermented foods and beverages contain considerable levels of organic acids, combined with salts and other antimicrobials have been largely considered microbiologically safe. Several LAB, either as indigenous microbiota or added as starter cultures, are able to produce bacteriocins that inhibit undesirable bacteria like Listeria, Staphylococcus, and Clostridium. Fermented foods are eventually characterized or labeled as probiotics, but a well-defined health benefit should be clearly associated with live microorganisms, and therefore, the terms fermented food and probiotics cannot be used interchangeably (Marco et al., 2021). For example, traditional, spontaneously fermented sausages likely contain multiple strains of LAB (including strains of L. acidophilus and L. plantarum), but these uncharacterized strains, present at indefinite doses, would not meet the requirements of probiotics. In contrast, if the sausages contain genetically characterized strains with established probiotic properties, such as L. acidophilus LA-5 or L. plantarum 299v, at an effective dose until the end of shelf life and there was no evidence for inhibitory interactions of the food matrix, this product would meet the minimum criteria for a probiotic fermented food.

For a microorganism to be considered a probiotic, as defined by WHO, FAO, and EFSA, it should meet a series of safety and functionality criteria, as well as those related to its desirable properties, as summarized in Fig. 1.2 (Markowiak & Ślizewska, 2017). To be used in food or as supplements with a specific health claim, prior confirmation is required through human studies, such as positive meta-analyses, randomized clinical trials, or strong evidence from observational studies (Hill et al., 2014; ISAPP, 2018). Probiotics safety and efficacy are both strain- and dose-dependent, as well as, although rare, their adverse events include diarrhea, sepsis, subacute bacterial endocarditis, and meningitis (Liu, Tran, & Rhoads, 2018).

Fig. 1.2

Fig. 1.2 Selection criteria and desirable properties for microbial probiotics. (Information compiled from Markowiak, P. & Ślizewska, K. (2017) Effects of probiotics, prebiotics, and synbiotics on human health, Nutrients. Poland: MDPI AG, 9(9). https://doi.org/10.3390/nu9091021.)

1.4: Safety aspects of probiotics

Insofar as probiotics as health promoters have been increasingly added to food products, especially fermented foods, as well as medicines, in addition to the fundamental importance of food safety issues and possible adverse effects of these microorganisms, it is necessary a further discussion about the safety of probiotics use for human consumption. According to the FAO/WHO (FAO/WHO, 2006), although food-associated lactobacilli and bifidobacteria have been historically considered as safe, theoretically, probiotics can generate four types of side effects: systemic infections, deleterious metabolic activities, excessive immune stimulation in susceptible individuals, and genetic transfer.

Since probiotics are alive when administered or consumed, their potential for infectivity or toxin production in the host cannot be ruled out. The safety of its use includes several factors, such as the potential vulnerability of the consumer or patient, the dose and duration of consumption, as well as the form and frequency of its administration. Furthermore, immunological effects must be considered, especially in cases of vulnerable populations, such as infants with underdeveloped immune function (Sanders et al., 2010).

Key safety factors to consider for probiotics utilization in foods include their origin (preferably from the healthy human gastrointestinal tract), nonpathogenicity, and antibiotic resistance. Some of these microorganisms, such as enterococci, can also behave as opportunistic pathogens for humans, containing antibiotic resistance elements and potential virulence factors, and then being questionable their usage as probiotics. Although bifidobacteria and lactobacilli have been considered safe and continued employed in foods, infection by some species has been reported, however, in rare cases (Peivasteh-Roudsari et al., 2020). The infection potential of some microorganisms used as probiotics is presented in Table 1.1.

Table 1.1

Compiled from Peivasteh-Roudsari, L., et al. (2020). Probiotics and food safety: An evidence-based review. Journal of Food Safety and Hygiene. https://doi.org/10.18502/jfsh.v5i1.3878. Knowledge.

According to Hill, the main risks that must be taken into account regarding the therapeutic use of probiotics are that such microorganisms can cause sepsis in compromised patients and the use of next-generation probiotics without a safety record (Hill, 2020). The cases where probiotics administration could be considered unsafe have been discussed and pointed as prematurity, immunocompromised individuals, critically ill patients, short bowel syndrome (SBS), and patients with cardiac valvular disease or requiring a central venous catheter (Van Den Nieuwboer & Claassen, 2019).

Regarding the use of microorganisms modified by genetic engineering, although these are widely used for the production of valuable metabolites, their food and clinical applications require strict safety and security measures. Genetic manipulation of probiotic strains has been described, and these recombinant microorganisms would have the appeal of presenting improved stress tolerance, production of antimicrobial substances, and enhanced antiinflammatory responses. Furthermore, recombinant probiotics may be used to deliver drugs or vaccines, target specific pathogens or toxins, and mimic cell surface receptors, offering an alternative therapeutic approach in the treatment of foodborne infections (Mathipa & Thantsha, 2017). However, engineered probiotic strains contain additional genetic elements that can induce antigenicity and immunomodulation; this could affect normal metabolic pathways, requiring very well-defined and controlled studies, such as metagenomic analyses to guarantee the safety of their use (Kumar et al., 2016). Moreover, recombinant strains should be labeled as genetically modified organisms (GMOs) and it should be demonstrated that they do not possess antibiotic selection markers or the ability to transfer genetically modified DNA to other bacteria.

1.5: Beneficial health properties and therapeutic potential of probiotics

Probiotics can be produced and commercialized as drugs, foods, medical foods, dietary supplements, infant formulas, or animal feed, by pharmaceutical and food industries (Télessy, 2019). However, fermented foods containing living organisms cannot be considered as probiotics if their effects have not been specifically studied or their quantity is unknown. Some fermented foods, such as yogurt, can be classified as probiotics based on certain specific effects, such as improving lactose digestion in individuals with lactose intolerance (Salehi et al., 2021).

According to the World Gastroenterology Organization, a probiotic required dose depends on the specific microbial strain and the product type (World Gastroenterology Organization, 2017). Although many commercially available products present between 1 and 10 billion colony forming units (CFU) per dose, some probiotic strains have shown effectiveness at lower levels, while others require larger amounts (Sarao & Arora, 2017). It is recommended that a probiotic product contains at least 10⁶ to 10⁷ CFU g− 1 of bacteria, or a total of 10⁸ to 10⁹ CFU, in order to provide a therapeutic effect, based on a minimum daily consumption of 100 g or 100 mL of probiotic foods (Flach et al., 2018).

The intestinal microbiota has important functions, as promoting food digestion, xenobiotics metabolism, and immunological system regulation. Proteins, peptides, and metabolites promote various cell signaling and pathways. Such crosstalk mechanism is responsible for maintaining the host’s microbial homeostasis (Belizário & Faintuch, 2018). Several factors can cause an imbalance in the microbiota composition, such as physicochemical properties (pH, temperature, peristalsis, bile acids, secretions, immune responses, motility); food pattern; mode of birth; infections; and use of antibiotics (Tesfaye et al., 2019). Probiotics can be used to improve or restore microbial homeostasis mainly in two ways: by occupying functional niches left by the endogenous community, thus preventing opportunistic pathogens from occupying such space (competitive exclusion), and by actively reducing opportunistic invasion through the production of certain compounds, like short-chain fatty acids (SCFAs) and other organic acids, bacteriocins, and/or reactive oxygen species (Vandenplas, Huys, & Daube, 2015). However, probiotics mechanisms of action are diverse, heterogeneous, and strain-specific (Hill et al., 2014; Plaza-Diaz et al., 2019).

According to Plaza-Diaz and collaborators, the main probiotics mechanisms of action are as follows: colonization and normalization of intestinal microbial communities; competitive exclusion of pathogens and production of bacteriocins; modulation of enzymatic activities; production of short- and branched-chain fatty acids; cell adhesion and mucin production; immune system modulation; and regulation of endocrine and neurological functions (Plaza-Diaz et al., 2019). The use of probiotics has already shown several benefits, such as antioxidant activity, modulation of the immune cells’ proliferation, antimicrobial peptides’ induction, release of antimicrobial factors, stimulation of IgA production, and inhibition of the epithelial cell nuclear factor ĸ-B activation (Salehi et al., 2021).

Many works have linked probiotics to the prevention of inflammatory and allergic diseases (such as atopic dermatitis and rhinitis), decreased incidence of diarrhea, infection control, antimicrobial action, protection against colon and bladder cancers, and control of blood lipids levels in cases of mild hypercholesterolemia (De Prisco & Mauriello, 2016; Plaza-Diaz et al., 2019; Sanders et al., 2018). Most consistent evidence regarding the use of probiotics is related to prevention or treatment of the following diseases: necrotizing enterocolitis, acute infectious diarrhea, antibiotic-associated diarrhea, acute respiratory tract infections, and childhood colic (Liu et al., 2018). According to Télessy, the most common indications for probiotics use and consumption are as follows: diarrhea, lactose intolerance, ulcerative colitis, Crohn’s disease, Helicobacter pylori infection, metabolic diseases, respiratory tract infections, allergies, and mental/neurological illnesses (Télessy, 2019). Some well-known and prospective health benefits of probiotics are discussed in detail in specific chapters of this book. The following sections present a brief description of some health benefits that have been associated with probiotics consumption.

The claims of beneficial health effects attributed to probiotics have been supported by increasing evidence. Although these health benefits are strain-specific as discussed before for probiotics properties, the value of probiotics for improving the intestinal health and the immune response, reduction of serum cholesterol, and cancer prevention has been described. While some of the health benefits are well-documented, others require additional studies in order to be established. In fact, there is substantial evidence to support the use of specific probiotic formulations in the treatment of diarrheal and inflammatory gut diseases, and improvement of lactose metabolism, but there is insufficient evidence to recommend them for use in other clinical conditions (Kechagia et al., 2013). Thus, additional data from in vivo evaluations and clinical trials should be obtained to confirm some potential beneficial effects of probiotics to human and animal health.

1.5.1: Nutritional benefits of probiotics

Gut microbiota has been shown to transport some nutrients to the host, like vitamin K, folate (vitamin B9), biotin (vitamin B7), riboflavin (vitamin B2), cobalamin (vitamin B12), as well as other B vitamins (Salehi et al., 2021). Certain microorganisms can produce vitamins, thus contributing to their bioavailability in the human host. Vitamin K, cobalamin, pyridoxine, biotin, folate, nicotinic acid, and thiamine are examples of vitamins that can be produced by intestinal microorganisms. Such property can affect the host health and, therefore, can be considered as a potential probiotic effect (Vandenplas et al., 2015; Zommiti et al., 2020). Other nutritional features would be the production of health-promoting compounds and the improvement of dietary calcium bioavailability (Bustamante et al., 2020; Vandenplas et al., 2015). The intake of probiotics has been associated with bone strengthening and reduced risks of bone loss and bone diseases. Although the exact mechanisms by which probiotics improve calcium absorption remain to be elucidated, the current evidence points to microbial production of metabolites like SCFAs and bioactive peptides, enzymes, or synthesis of vitamins that are involved in calcium metabolism and are required for bone matrix formation (Dubey & Patel, 2018).

The intestinal microbiota plays important roles in vitamins production, indigestible carbohydrates breakdown, and metabolism of toxins and drugs, but is also involved in the manufacture of neuroactive compounds like gamma-aminobutyric acid (GABA), serotonin, dopamine, acetylcholine, and SCFAs (Radisavljevic, Cirstea, & Finlay, 2019), such as acetate, propionate, and butyrate. Gut microbiota facilitates the nutrients’ absorption and metabolism, also providing necessary and inaccessible other nutrients, such as essential amino acids, which cannot be synthesized by the human body and are necessary for the synthesis of neurotransmitters like serotonin by tryptophan (Rios et al., 2017).

The maintenance of intestinal microbiota in a stable and fermentative manner involves a diet based on the consumption of plant foods, especially those rich in dietary fiber and polyphenols, which are processed by enzymes produced by such microbiota. Under anaerobic conditions, species belonging to the Bacteroides, Clostridiaceae, and Lactobacillaceae families produce SCFAs. Such substances play a key role in controlling proliferation, differentiation, and maintaining mucosal integrity (Belizário & Faintuch, 2018). The genera Lactobacillus and Bifidobacterium can produce GABA, while Escherichia, Bacillus, and Saccharomyces spp. are producers of norepinephrine, and Escherichia, Bacillus, Lactococcus, Lactobacillus, and Serratia can synthesize dopamine (Kim et al., 2018). The deficit production of SCFAs, tryptophan metabolites, GABA, norepinephrine, dopamine, acetylcholine, and serotonin, all related to microbial metabolism, has been linked with gastrointestinal problems, metabolic diseases, and neuropsychiatric disorders (Belizário & Faintuch, 2018).

1.5.2: Antioxidant properties of probiotics

Oxidative stress is characterized by an intracellular imbalance, where reactive oxygen species (ROS), such as superoxide anions and peroxide or hydroxyl radicals, are present at high levels, causing damage to lipids, proteins, and DNA. Probiotics can be resistant to ROS, modulating host’s defenses against oxidative stress through antioxidant properties, been this activity specific to each strain (Mishra et al., 2015). Despite is already known that probiotic microorganisms exhibit antioxidant potential, the mechanisms by which such property occurs have not yet been fully elucidated (Kim et al., 2020; Wang et al., 2017). The main modes of action presented by probiotics against oxidative radicals are believed to be through the following characteristics: metal ion chelating ability, antioxidant enzymes system, antioxidant metabolites, antioxidant signaling pathway mediation, regulation of ROS-producing enzymes and of intestinal microbiota (Wang et al., 2017).

LAB strains can increase the activity of antioxidant enzymes or modulate and reduce circulatory oxidative stress, protecting cells from induced damage. In fact, it has been proposed that LAB probiotics exert antioxidant effects by different modes of action, like elimination of free radicals, metal ions chelation, enzymatic regulation, and modulation of intestinal microbiota, as illustrated in Fig. 1.3. Some studies indicate that lactobacilli and bifidobacteria can prevent the onset and development of cancer, through the formation of an intestinal barrier to harmful agents, and the modulation of the immune response, with an increase in the activity of NK cells. In this sense, such bacteria could inactivate carcinogens and induce apoptosis, having antiproliferative and antioxidant effects on cancer cells. Furthermore, they are capable of secreting the superoxide dismutase (SOD) enzyme, enhancing the inherent cellular antioxidant defense, as well as releasing and promoting the production of glutathione (GSH), an important nonenzymatic cellular antioxidant (Nowak et al., 2019).

Fig. 1.3

Fig. 1.3 Possible modes of action of the antioxidant activity exerted by probiotic lactic acid bacteria. (According to Feng, T., & Wang, J. (2020) Oxidative stress tolerance and antioxidant capacity of lactic acid bacteria as probiotic: A systematic review. Gut Microbes. Informa UK Limited, 12(1), p. 1801944. https://doi.org/10.1080/19490976.2020.1801944.)

There are different methods used to measure the antioxidant activity exerted by probiotics, which can be divided into biochemical techniques and signaling techniques. Some examples of tests are cell free radical generation and RNA/protein expression analysis in eukaryotic cell co-culture or animal models. However, more complex tests are needed for probiotics than for molecular antioxidants (Zolotukhin, Prazdnova, & Chistyakov, 2018). To date, there are no uniform and comprehensive testing standards, making it impossible to compare the antioxidant capacity of different probiotics strains. In addition to the lack of a standardized and calibrated procedure, as well as evaluation criteria for the determination of antioxidant activity, it is not possible to compare the results between different studies. Thus, detection strategies and comparative methods for the evaluation of antioxidant properties of probiotics need to be more investigated (Feng & Wang, 2020).

1.5.3: Probiotics and gastrointestinal health

The human intestinal microbiota plays an important role in the development of lymphoid tissues associated with the intestine, which are responsible for a functional immunological system. Intestinal and immune epithelial cells express a variety of receptors, which mediate interactions between immunological system and commensal microbiota (Belizário & Faintuch, 2018). It is believed that certain health benefits exerted by probiotics can be attributed to the presence of EPS structures in the envelope that surrounds the bacteria. Extracellular proteins or those associated with the surface of intestinal microorganisms have crucial functions in their interaction with the host, leading to specific signaling pathways activation (Delgado et al., 2020).

Gut microbiome dysbiosis can be caused by medication, infections, lifestyle, surgery, and diet. Such disturbance has been related to the pathogenesis of many metabolic disorders and may result in acute and chronic diseases, like inflammatory bowel disease (IBD), irritable bowel syndrome (IBS), diabetes, and obesity (Sanders et al., 2019). However, there are many clinical indications, supported by consistent evidence, for the beneficial use of certain probiotic strains in some gastrointestinal disorders such as necrotizing enterocolitis, antibiotic-associated diarrhea, H. pylori infection, defecation frequency, childhood colic, ulcerative colitis, IBS, acute diarrhea, and prevention of diarrhea associated with Clostridium difficile. According to Vandenplas and collaborators, some probiotic strains are lactase-positive and have been successfully applied to relieve symptoms of lactose intolerance, such as abdominal cramping, nausea, and bloating (Vandenplas et al., 2015). Indeed, the EFSA authorized a health claim for S. thermophilus and L. bulgaricus as components of yogurt that can alleviate lactose maldigestion symptoms (Sanders et al., 2019).

More detailed information on the potential benefits of probiotics for human intestinal health, including data from clinical trials, will be provided in other chapters of this book. In the next section, the use of probiotics as a strategy to control gastric disease triggered by H. pylori infection is presented.

1.5.3.1: Positive effects of probiotics to control Helicobacter pylori infection

Helicobacter pylori is a Gram-negative rod-type bacteria, spiral-shaped, flagellated, and strictly microaerophilic. It is admirably adapted to the gastric epithelium, settling inside or below mucosa layer, where it releases some enzymes (like urease) and toxins. After its colonization, host’s immune response generates an inflammatory reaction that further increases tissue damage, that can lead to gastritis, due to a physiological change in gastric acid secretion. In addition, it is also associated with more severe gastrointestinal disorders, such as peptic ulcer, gastric mucosa-associated lymphoid tissue, and gastric cancer (Goli & Moniri, 2016; Saxena, Mukhopadhyay, & Nandi, 2020).

Some studies revealed that half of the world’s population is infected by the H. pylori (Goli & Moniri, 2016); however, only 10%–20% of infected individuals have gastric disease and the rest remain asymptomatic (Nair et al., 2016). The main causes of this infection are the water, poor hygiene, poor nutrition, and geographical location (Saxena et al., 2020). Treatment of H. pylori infection may be difficult due to the acidic environment of the stomach lumen. Furthermore, antibiotic therapies are losing their effectiveness due to the increase in antimicrobial resistance (Goli & Moniri, 2016). Also, treatment with antibiotics can lead to a microbiota dysbiosis, which can generate other diseases (Nair et al., 2016). In this sense, the use of probiotics can be considered an interesting approach.

A number of fermented foods and beverages are natural sources of probiotic microorganisms. Many of these, isolated directly from fermented foods, especially dairy products, exhibit anti-H. pylori effects. A study carried out with the Mexican population observed that the weekly consumption of one portion or more of fermented yogurt had a protective effect against H. pylori infection (Nair et al., 2016). There are several clinical studies about the effect of probiotics treatment (alone or in combination with other drugs) for eradication therapy of H. pylori infection. Probiotics have been shown to increase the eradication rate and prevent many adverse effects, such as diarrhea, nausea, vomiting, and taste disturbances. Although more studies are still needed to establish which strains, dosages, and duration of probiotics are used in this therapy, some of the known mechanisms of action include competition for nutrients, production of antibacterial compounds, adhesion competitive inhibition and stimulation of host functions and immunity (Kamiya, Yonezawa, & Osaki, 2019).

Wu and co-workers analyzed the intestinal microbiome of patients with duodenal ulcer, after using anti-H. pylori triple therapy (proton pump inhibitors, clarithromycin, and amoxicillin), compared to the use of this treatment plus probiotic bacteria (Bacillus subtilis and Enterococcus faecium) and the control group (healthy individuals). The authors found that the therapy supplemented with probiotics was able to protect and regenerate, after 10 weeks, the intestinal microbiota, while the use of triple therapy decreased and changed its diversity, compared to the control group (Wu et al., 2019).

A meta-analysis about the use of triple therapy supplemented with probiotics for H. pylori eradication in children found that, compared to placebo, triple therapy plus probiotics significantly increased H. pylori eradication rates and reduced the incidence of side effects (Feng et al., 2017). Moreover, L. casei showed the best eradication rates and strains of L. acidophilus plus L. rhamnosus for side effects. Thus, the use of probiotics associated with anti-H. pylori triple therapy can be recommended in pediatrics, whose effectiveness is associated with specific probiotic supplementation.

1.5.4: Probiotics and oral health

Probiotics can assist in the inhibition of colony formation by bacteria that cause periodontitis and dental caries and can be formulated as pastilles and mouthwashes, thus promoting a longer probiotic activity and a healthy oral environment. Probiotics can act in the oral cavity through antagonism of pathogens, coaggregation with oral bacteria, modulation of oral biofilm functions and plaque ecology, interaction with the oral epithelium, increase barrier function and host immune responses, or inhibition of cytokines induced by pathogens (Mishra, Rath, & Mohanty, 2020). Current works, including clinical trials, strongly suggest an active role of probiotics in oral infections’ prevention and treatment. Microorganisms used as oral probiotics can create a biofilm, acting as a protective coating and replacing any pathogen in the biofilm. Nevertheless, a selection of the most suitable probiotic for oral health requires more studies (Chugh et al., 2020).

Experimental studies and clinical trials have already shown that certain bacteria, such as Lactobacillus spp. and Bifidobacterium spp., could control the growth of oral microorganisms, including cariogenic streptococci. Thus, probiotics can play an important role in the clinical management of dental caries and periodontal diseases, although the evidence is less consistent for halitosis (Allaker & Stephen, 2017). Barboza and collaborators, when analyzing experimental studies that used probiotics to treat gingivitis, observed that the improvement in clinical parameters, compared to placebo, was due to the modulation of the host’s response and not due to the antiplaque effect (Barboza et al., 2020). However, long-term efficacy and safety of probiotics utilization still need to be established regarding their prevention or treatment of oral diseases. A better understanding of their mechanisms of action should be obtained to determine safe clinical recommendations (Allaker & Stephen, 2017; Chugh et al., 2020).

1.5.5: Probiotics and skin health

Probiotics have great potential to treat and prevent skin diseases, like atopic dermatitis or eczema, acne, and allergic inflammation, but also can act in skin hypersensitivity, skin damage, wound protection, and as a cosmetic product (Roudsari et al., 2015). However, the relationship between the use of topical probiotics and skin diseases has not been fully studied. Ideal dosage and strain for skin conditions have yet to be determined (Knackstedt, Knackstedt, & Gatherwright, 2020).

Rosacea, acne, and atopic dermatitis are the most frequent skin disorders, being mostly treated with antibiotics, that disrupt the normal skin microbiota. In this sense, a new line of innovative cosmetics, the so-called prebiotic cosmetics, was created with the objective of rebalancing such microbiome, inhibiting the growth of transitory or pathogenic species, by promoting multiplication of beneficial bacteria (Bustamante et al., 2020). Particularly, lactobacilli and bifidobacteria have been used in cases of skin inflammation, atopic dermatitis, and allergic contact dermatitis. Atopic dermatitis is an inflammatory skin disease, which occurs in the early stages of life, being associated with allergic rhinitis, food allergies, and asthma (Lolou & Panayiotidis, 2019). Atopic dermatitis is estimated in 15%–20% of children and 1%–3% of adults worldwide, and its prevalence has recently increased 2–3 times (Puebla-Barragan & Reid, 2019). A study has proved that a supplementation with L. rhamnosus and L. reuteri was able to reduce 56% of eczema severity in children suffering from such disease. The relationship between the intestinal microbiota and the increased risk of developing eczema in babies has already been demonstrated, which had a higher clostridia concentration compared to control babies (Lolou & Panayiotidis, 2019).

1.5.6: Probiotics and respiratory tract health

Respiratory tract infections correspond to mucosal surfaces infections like rhinitis, sinusitis, tonsillitis, pharyngitis, laryngitis, and common cold. Upper respiratory tract infections have been estimated at around 17 billion cases per year worldwide, and the treatment will depend on the infection cause, usually with antibiotics or antivirals. The increase in bacterial resistance to antibiotics and the reduced availability of vaccines for most viruses require the search for new safe, efficient, and appropriate therapies, being the use of prebiotics and probiotics an interesting innovative strategy. Several studies have evaluated the probiotics effect in the prevention of respiratory infections, but the results are inconclusive to date (Bustamante et al., 2020; Li et al., 2020).

However, according to Sanders and collaborators, there is strong evidence that probiotics can reduce the incidence and duration of upper respiratory tract infections (Sanders et al., 2019). A clinical study showed a reduction in the incidence and duration of symptoms of the common cold by consuming L. plantarum and L. paracasei. Another clinical study showed that the use of probiotics (L. paracasei, L. casei, and L. fermentum) was able to reduce the incidence of upper respiratory infection by increasing the levels of IFN-γ in the blood and sIgA in the gut (Zhang et al., 2018).

In addition, probiotics consumption can reduce the risk of respiratory tract infections in children. Probiotics can stimulate pulmonary immunity by increasing the regulatory T response in the airways, as well as decrease the risk of respiratory infections through intestinal immunity improvement. Besides, some probiotic strains also possess antiviral activity by direct probiotic-virus interaction, production of antiviral inhibitory metabolites, and/or immune system stimulation. Thus, their use could provide some alternatives and support therapy against COVID-19 (Sundararaman et al., 2020), for example.

According to Baud and collaborators, it is already known that the oral use of probiotic microorganisms is associated with the reduction of incidence and severity of viral respiratory infections, and then, its administration together with recognized prebiotics (synbiotics) could be recommended as part of the general strategy to flatten the COVID-19 pandemic curve (Baud et al., 2020). It is already known that the gut mycobiome of patients with COVID-19 can be significantly altered and those who had more than two Aspergillus species in abundance had more severe disease. Nevertheless, little is known about the use of probiotics/synbiotics in relation to the prevention and treatment of SARS-CoV-2 infection. Moreover, according to the ISAPP, there is still insufficient scientific evidence to recommend the use of both probiotics and prebiotics in the treatment and prevention of COVID-19 or inhibition of the SARS-CoV-2 virus, needing more placebo-controlled trials (ISAPP, 2020). Then, additional clinical trials are needed in order to confirm the probiotics role to determine the optimal strains, dosing regimens, time and duration of the intervention (Hu et al., 2021).

1.5.7: Probiotics and women urogenital health

A beneficial vaginal microbiota is dominated by Lactobacillus spp., while vaginal dysbiosis is characterized by an overgrowth of multiple anaerobes, being associated with an increased risk of urogenital and reproductive health issues (Tachedjian et al., 2017) Lactobacilli create a biofilm on the mucosal surface, protecting the vagina against pathogenic microorganisms through organic acids’ secretion, production of antimicrobial substances, competition for nutrients, coaggregation, immune system stimulation, among other mechanisms (Bustamante et al., 2020; Nader-Macías & Juárez Tomás, 2015).

In 1973, a urologist called Andrew Bruce started to consider lactobacilli as probiotics for women’s urogenital tract health. He believed that, in the vagina environment where E. coli is dominant after repeated urinary tract infections and antibiotic treatments, lactobacilli replacement could restore homeostasis and protect the host (Puebla-Barragan & Reid, 2019). An eubiotic vaginal environment contains high lactic acid concentration, formed by lactobacilli, which acidifies the vagina (pH ≤ 4.5). However, the antiviral, antibacterial, and immunomodulatory properties of lactic acid in urogenital health need further investigation (Tachedjian et al., 2017). There is some evidence that probiotics supplementation can restore the vaginal microbiota and modulate the local mucosa immune response. Such supplementation may be administered orally as a probiotic food, intravaginal as vaginal suppositories, or applied topically as a gel (Bustamante et al., 2020).

A study used a vaginal isolated strain, L. crispatus BC4, in order to produce a probiotic Squacquerone cheese and evaluate its viability in such food products and under simulated gastrointestinal conditions. The authors believe that the use of such cheese as a probiotic food could be able to improve women’s health by preventing gynecological infections (Patrignani et al., 2019), but in vivo studies are still needed. A clinical trial conducted with 36 women evaluated the effect of a yogurt containing Lactobacillus strains on bacterial vaginosis (BV). After 4 weeks of intervention 0 of 17, women had BV in the yogurt group versus 6 of 17 in the control group. Thus, the intake of such probiotic yogurt improved BV recovery rate and symptoms and probably improved the vaginal microbiome (Laue et al., 2018).

1.5.8: Probiotics and mental/neurological health

Despite progress in drug development, most individuals being treated for mood disorders, like major depressive disorder and bipolar disorder, do not achieve complete symptomatic remission and functional recovery. Besides, a substantial proportion of patients are unable to tolerate existing drugs (Rios et al., 2017). There are some neurological disorders that appear to be related to the intestinal microbiota, like neurodegenerative and mood disorders, where gut microbes could affect brain health by common mechanisms (Naseribafrouei et al., 2014; Radisavljevic et al., 2019). In fact, several gastrointestinal disorders have a high prevalence of psychiatric symptoms, as gut dysbiosis is present in many neurological diseases. Moreover, there is growing evidence that probiotics are effective in reducing depression and anxiety symptoms (Kim et al., 2018; Rios et al., 2017).

Gut microbiota has a new close interaction with the immunological system, and inflammation is associated with several neurological disorders, including Parkinson’s and Alzheimer’s diseases, multiple sclerosis, autism spectrum disorder, anxiety, and depression. This may be the common mechanistic pathway of the gut-microbiota-brain axis (Radisavljevic et al., 2019). This axis structure involves the gastrointestinal tract, the central, autonomic, and enteric nervous systems, plus the neuroendocrine and immune systems (Kim et al., 2018). Recently, a review paper reinforced the idea of the potential use of probiotics or synbiotics as new prophylactics in the treatment of Alzheimer’s disease, due to their antiinflammatory and antioxidant capabilities, by improving cognition and metabolic activity, as their production of essential metabolites for the gut-brain barrier permeability (Arora, Green, & Prakash, 2020).

In addition, gut microbiota is also associated with neuroactive compounds’ production, such as GABA, serotonin, dopamine, acetylcholine, tryptophan metabolites, and SCFAs (Radisavljevic et al., 2019). There is growing evidence that the gut microbiota and associated metabolites may have a role in the pathophysiology of depression. Some evidence from animal models has begun to elucidate the role of microbiome abnormalities in the etiology of depression. Alongside the appearance of anhedonia and anxiety-like behavior, the oral gavage of fecal microbiota from patients with major depressive disorder to antibiotic-treated rats induced a reduced richness and diversity of gut microbiota and elevated plasma kynurenine and kynurenine/tryptophan ratio (Kelly et al., 2016). Tryptophan metabolism along the serotonin (5-hydroxytryptamine), kynurenine, and indole pathways can be regulated by the gut microbiota, reinforcing the possible transference of depressive-like behavioral and physiological traits via the microbiota. Nevertheless, communication routes between gut microbiota and the brain are not yet fully elucidated, probably through neural, endocrine, and immunological pathways that can be affected by the microbiota or by their metabolites (Caspani et al., 2019; Liu, Cao, & Zhang, 2015).

1.6: Probiotics legislation and challenges

In the global market, probiotics can be found in three main product categories: food, dietary supplements, and pharmaceuticals. The regulatory category, especially for the more recent ones, such as cosmetics containing probiotics, is unclear. There is no global consensus on regulatory issues for manufacturing and claim requirements for probiotics. In addition, probiotic products quality, such as product labeling reliability and accuracy, can considerably variate between product category and geographic region (Sanders et al., 2018).

Probiotics are mainly classified as foods or dietary supplements in the USA and Europe, as natural health products in Canada, and as foods for specific health use in Japan, where such categorization complies with much less stringent regulations (Zommiti et al., 2020). Traditional probiotics are usually classified into categories (as QPS for Europe and GRAS for the USA) and cannot be used in most health claims. Japan acts as a world market leader, where probiotics are considered both food and medicine, regularly approving health claims for new food products (Martín & Langella, 2019).

FAO/WHO and the International Life Science Institute have launched a general approach for assessing probiotics safety. Their criteria are lined with the European Union Product Safety Forum of Europe (EU-PROSAFE) recommendations. Other regulatory bodies, such as Health Canada, United States Food and Drug Administration, and Ministry of Health and Welfare (Japan), from several countries are also committed to establishing probiotics safety guidelines (Pradhan et al., 2020).

The FAO/WHO recommendation is that specific health claims for foods containing probiotics are allowed only when sufficient scientific evidence is available. Most countries also have also only general health claims regarding probiotic foods. In December 2006, the European Parliament and Council published a regulation (1924/2006), which aimed to consolidate nutrition and health claims to better protect consumers of the European food market (Vandenplas et al., 2015). However, according to Martín and Langella, the only probiotic health claim approved by the EFSA is the lactose intolerance prevention through yogurt ingestion (Martín & Langella, 2019).

Still regarding the European Union (EU) regulation, health claims for probiotic products can only be authorized for use after a careful scientific evaluation made by the Panel on Dietary Products, Nutrition and Allergies (NDA) from EFSA. Such recommendations are important to approximate the claims of probiotic food supplements and medications because many companies have found ways to avoid the EFSA restrictions, such as registering dietary supplements as medical devices, in which claims can be made without providing solid scientific evidence (Vandenplas et al., 2015). According to Sanders and collaborators, the standard of evidence applied in the EU is the most rigorous and all studies must be performed on healthy individuals to be considered, but even in the USA, there are no FDA-approved probiotic drugs (Sanders et al., 2018). In order to launch a nontraditional probiotic on the European market as a new food, the regulatory process is as complicated or even more as that required for a drug, even if the microorganism is a human commensal. Therefore, regulatory framework must be updated so as not to hinder research and innovation, in parallel with ensuring security (Martín & Langella, 2019). Due to the absence of well-established guidelines for the evaluation of probiotics in vivo, the protocols of the Organization for Economic Cooperation and Development (OECD) have been used, which are made to assess the safety of chemicals in rodents. Some tests based on these guidelines, such as reverse mutation assay, chromosomal aberration assay, and micronucleus test, have also been carried out by certain studies to assess the genotoxic potential of probiotic strains. In addition, the genome screening of probiotic bacteria for the presence of virulence and resistance genes is also used to check for the presence of unexpressed safety risk factors (Pradhan et al., 2020).

This lack of cohesion in the regulation of probiotics creates many difficulties, not only for its commercialization at a global level, but also in terms of inspection. It is known that the number of viable bacterial cells per dose in many probiotic foods is significantly lower than that shown on the labels. In addition, microbial contamination and reduced functional properties of probiotic products, which can be influenced by processing, handling, and food matrices, represent the main challenges for their application (Zommiti et al., 2020). Jackson and collaborators suggest that probiotic manufacturing companies undergo impartial third-party certification, as it is their responsibility to ensure that their products meet label claims throughout their shelf life (Jackson et al., 2019). The authors believe that it is the role of the industry to improve transparency regarding the quality of the probiotic product, even in the absence of regulatory requirements for that.

The main adverse conditions for probiotics during food process or storage and to pass through the gastrointestinal tract are relative humidity, high temperature, light, oxygen, osmotic stress, pH, gastric and bile acids, and digestive enzymes (Yao et al., 2020). Therefore, factors such as encapsulation method and wall materials, pH, initial cell population, probiotic strain, and food matrix are particularly important and must be carefully considered (Terpou et al., 2019). The choice of strains, culture conditions, and product manufacture are of great importance in order that the health benefits claimed by probiotics effectively reach the consumer (Fenster et al., 2019). Besides, there are still several gaps about the mechanisms that support probiotics health benefits. In addition, many of these have not been tested in humans, requiring more conclusive evidence to confirm that a particular mechanism is related to a specific health outcome (Sanders et al., 2018).

1.7: Conclusion and perspectives

In this chapter, a brief introduction to the history of fermented and probiotic foods was presented, as well as a discussion on the probiotics concept, beneficial properties to human health, its relationship with the human intestinal microbiome, global market, food safety and regulatory issues and main existing challenges. Several studies have been proving the association between an unbalanced gut microbiota with some diseases, especially chronic diseases, like IBD, IBS, diabetes, and obesity. In this sense, the use of probiotics can be an interesting approach to restore the microbiome homeostasis, through the consumption of food or supplements containing these microorganisms. Thus, the potential of probiotics has been recognized as so important for the maintenance of human health that, according to Spacova and collaborators, all countries should take measures in order to implement programs that allow poor people access to fermented foods and probiotics, reducing the risk of diseases such as diabetes, malnutrition, and infections (Spacova et al., 2020). As it was discussed here, many health benefits are currently considered for the probiotics use, including treatments for diarrhea, lactose intolerance, ulcerative colitis, Crohn’s disease, H. pylori infection, metabolic diseases, respiratory tract infections, allergies, and mental/neurological illnesses. With the continuation of studies on the microbiome and the utilization of probiotics in the prevention and treatment of diseases, two other areas that will see significant advances over the next years are the use of probiotics for cardiovascular health and for reducing absorption and damage from environmental toxins (Puebla-Barragan & Reid, 2019). However, to have robust evidence that changes in the gut microbiome are able to reduce the incidence or mitigate disease, well-designed randomized clinical trials are still required.

References

Allaker R.P., Stephen A.S. Use of probiotics and oral health. In: Current oral health reports. United Kingdom: Springer Science and Business Media B.V.; 2017:309–318. doi:10.1007/s40496-017-0159-6 4(4).

Arora K., Green M., Prakash S. The microbiome and Alzheimer’s disease: Potential and limitations of prebiotic, synbiotic, and probiotic formulations. Frontiers in Bioengineering and Biotechnology. 2020;8. doi:10.3389/fbioe.2020.537847.

Barboza E.P., et al. Systematic review of the effect of probiotics on experimental gingivitis in humans. Brazilian Oral Research. 2020;34. doi:10.1590/1807-3107BOR-2020.VOL34.0031.

Baud D., et al. Using probiotics to flatten the curve of coronavirus disease COVID-2019 pandemic. Frontiers in Public Health. 2020;8. doi:10.3389/fpubh.2020.00186.

BBC. Probiotics in food, beverages, dietary supplements and animal feed. Available at: https://www.bccresearch.com/market-research/food-and-beverage/probiotics-market-ingredients-supplements-foods-report.html. 2020.

Belizário J.E., Faintuch J. Microbiome and gut dysbiosis. Experientia Supplementum (2012). 2018;109:459–476. doi:10.1007/978-3-319-74932-7_13.

Bustamante M., et al. Probiotics and prebiotics potential for the care of skin, female urogenital tract, and respiratory tract. Folia Microbiologica. 2020;65(2):245–264. doi:10.1007/s12223-019-00759-3.

Caspani G., et al. Gut microbial metabolites in depression: Understanding the biochemical mechanisms. Microbial Cell. 2019;6(10):454–481. doi:10.15698/mic2019.10.693.

Chugh P., et al. A critical appraisal of the effects of probiotics on oral health. Journal of Functional Foods. 2020;70. doi:10.1016/j.jff.2020.103985.

De Prisco A., Mauriello G. Probiotication of foods: A focus on microencapsulation tool. Trends in Food Science and Technology. 2016;48:27–39. doi:10.1016/j.tifs.2015.11.009.

Delgado S., et al. Molecules produced by probiotics and intestinal microorganisms with immunomodulatory activity. Nutrients. 2020;12(2):doi:10.3390/nu12020391.

Dubey M.R., Patel V.P. Probiotics: A promising tool for calcium absorption. The Open Nutrition Journal. 2018;59–69. doi:10.2174/1874288201812010059.

Elshaghabee F.M.F., et al. Bacillus as potential probiotics: Status, concerns, and future perspectives. Frontiers in Microbiology. 2017;8. doi:10.3389/fmicb.2017.01490.

FAO/WHO. Health and nutritional properties of probiotics in food including powder milk with live lactic acid bacteria. Available at: http://www.who.int/foodsafety/publications/fs_management/en/probiotics.pdf. 2001.

FAO/WHO. Probiotics in food: Health and nutritional properties and guidelines for evaluation. Available at: http://www.fao.org/3/a0512e/a0512e.pdf. 2006.

Feng T., Wang J. Oxidative stress tolerance and antioxidant capacity of lactic acid bacteria as probiotic: A systematic review. Gut Microbes. 2020;12(1):1801944. doi:10.1080/19490976.2020.1801944.

Feng J.R., et al. Efficacy and safety of probiotic-supplemented triple therapy for eradication of Helicobacter pylori in children: A systematic review and network meta-analysis. European Journal of Clinical Pharmacology. 2017;73(10):1199–1208. doi:10.1007/s00228-017-2291-6.

Fenster K., et al. The production and delivery of probiotics: A review of a practical approach. Microorganisms. 2019;7(3):doi:10.3390/microorganisms7030083.

Flach J., et al. The underexposed role of food matrices in probiotic products: Reviewing the relationship between carrier matrices and product parameters. Critical Reviews in Food Science and Nutrition. 2018;58(15):2570–2584. doi:10.1080/10408398.2017.1334624.

Gibson G.R., et al. Expert consensus document: The International Scientific Association for Probiotics and Prebiotics (ISAPP) consensus statement on the definition and scope of prebiotics. Nature Reviews. Gastroenterology & Hepatology. 2017;14(8):491–502. doi:10.1038/nrgastro.2017.75 United Kingdom: Nature Publishing Group.

Global Market Insights. Probiotics market statistics 2026: Industry growth report. Available at: https://www.gminsights.com/industry-analysis/probiotics-market. 2019.

Goli Y.D., Moniri R. Efficacy of probiotics as an adjuvant agent in eradication of Helicobacter pylori infection and associated side effects. Beneficial Microbes. 2016;7(4):519–527. doi:10.3920/bm2015.0130.

Hill C. Balancing the risks and rewards of live biotherapeutics. Nature Reviews. Gastroenterology & Hepatology. 2020;17(3):133–134. doi:10.1038/s41575-019-0254-3.

Hill C., et al. The International Scientific Association for Probiotics and Prebiotics consensus statement on the scope and appropriate use of the term probiotic. Nature Reviews Gastroenterology & Hepatology. 2014;11(8):506–514. doi:10.1038/nrgastro.2014.66.

Hu J., et al. Review article: Probiotics, prebiotics and dietary approaches during COVID-19 pandemic. Trends in Food Science and Technology. 2021;108:187–196. doi:10.1016/j.tifs.2020.12.009.

ISAPP. ISAPP position statement on minimum criteria for harmonizing global regulatory approaches for probiotics in foods and supplements. Available at: https://isappscience.org/minimum-criteria-probiotics. 2018.

ISAPP. ISAPP provides guidance on use of probiotics and prebiotics in time of COVID-19. Available at: https://isappscience.org/isapp-provides-guidance-on-use-of-probiotics-and-prebiotics-in-time-of-covid-19. 2020.

Jackson S.A., et al. Improving end-user trust in the quality of commercial probiotic products. Frontiers in Microbiology. 2019;10. doi:10.3389/fmicb.2019.00739.

Johnson B.R., Klaenhammer T.R. Impact of genomics on the field of probiotic research: Historical perspectives to modern paradigms. Antonie Van Leeuwenhoek. 2014;106(1):141–156. doi:10.1007/s10482-014-0171-y.

Kamiya S., Yonezawa H., Osaki T. Role of probiotics in eradication therapy for Helicobacter pylori infection. Springer Science and Business Media LLC; 2019.243–255. doi:10.1007/5584_2019_369.

Kechagia M., et al. Health benefits