Nutritional and functional properties of fermented dairy products: Current scientific evidence, health benefits and future perspectives

Introduction

Fermented dairy products are among the oldest examples of purposeful food biotransformation and continue to play a major role in human diets because fermentation improves preservation, palatability, and product diversity while retaining the core nutrient richness of milk (Nagpal, 2012; Saleem et al., 2024, Kaur, 2022) [22,31,17] . In modern food science, their importance has expanded further because fermented dairy foods are now evaluated not only as sources of high-quality protein, calcium, phosphorus, potassium and Among these products, yogurt and cultured fermented milk currently have the strongest human evidence base. In a qualitative systematic review conducted using PRISMAguided methods, Savaiano and Hutkins (2021) [33] screened 1,057 abstracts and included 108 studies, concluding that the clearest causal evidence concerns lactose digestion and tolerance, while consistent associations also exist for reduced risk of type 2 diabetes, improved weight maintenance, and favorable gastrointestinal, cardiovascular, and bone-related outcomes. However, the same review also shows that the literature is not uniformly conclusive: many studies were neutral, some were methodologically limited, and benefits were not identical across all fermented dairy categories. This heterogeneity is one of the central scientific challenges in the field. The term "fermented dairy products" encompasses foods with very different microbiological ecologies, processing technologies, textures, nutrient concentrations, and consumption patterns. Yogurt made with the classical thermophilic starter pair differs fundamentally from kefir produced with mixed bacterialyeast cultures, and both differ from ripened cheese in terms of fermentation kinetics, metabolite formation, and likely mechanisms of action (Saleem et al., 2024; Pang et al., 2025) [31,25] . Consequently, broad claims about fermented dairy as a single category may obscure important differences between products, strains, and target populations (Saleem et al., 2024; Savaiano & Hutkins, 2021) [31,33] . The current rise of microbiome science has further intensified interest in fermented dairy. Products containing live microorganisms or fermentation-derived metabolites are now being investigated as modulators of gut ecology and host response, yet enthusiasm has sometimes outpaced evidentiary precision. Mechanistic plausibility is strong for several pathways, including lactose hydrolysis, microbial metabolite exposure, and peptide generation, but translational certainty is much lower for some widely cited claims related to inflammation, cancer prevention, and systemic disease modification (Saleem et al., 2024; Savaiano & Hutkins, 2021; Pang et al., 2025) [31,33,25] . This makes critical synthesis essential. The public health relevance of this topic is also substantial. Fermented dairy products combine nutrient density with broad cultural acceptance, are available in both traditional and industrial forms, and may provide options for individuals who tolerate fermented dairy better than unfermented milk (Savaiano & Hutkins, 2021) [33] . At the same time, dietary guidelines and policy discussions have generally emphasized dairy in aggregate rather than distinguishing between fermented and non-fermented dairy matrices, even though the evidence suggests that these foods may not be physiologically equivalent in all contexts (Savaiano & Hutkins, 2021) [33] . Against this background, the present review aims to critically analyze the nutritional and functional properties of fermented dairy products, evaluate the strength and limitations of current health evidence, and identify the major scientific and translational questions that should guide future research. Particular emphasis is placed on publication-quality synthesis, methodological transparency, and careful separation of well-supported conclusions from hypotheses that remain promising but insufficiently confirmed (Page et al., 2021; Saleem et al., 2024; Savaiano & Hutkins, 2021) [24,31,33] .

Review Methodology 2.1 Literature Search Strategy

This review was designed using a PRISMA-inspired evidence-synthesis framework aligned with the PRISMA 2020 Statement, which updated reporting guidance for systematic reviews and revised expectations for transparency in study identification, selection, appraisal, and reporting (Page et al., 2021) [24] . Because the present article is a broad scholarly review rather than a formal metaanalysis, PRISMA was applied as a methodological structure for transparent literature mapping rather than as a strict quantitative synthesis template (Page et al., 2021) [24] . The search strategy was constructed around the major concept domains specified in the review question: fermented dairy products, yogurt, cultured fermented milk, kefir, dahi, cheese, cultured buttermilk, probiotics, functional foods, lactic acid bacteria, dairy microbiology, bioactive peptides, and gut health. These terms were used singly and in Boolean combinations across PubMed, Scopus, Web of Science, ScienceDirect, SpringerLink, Wiley Online Library, and Google Scholar, with primary emphasis on studies published from 2010 onward and prioritization of literature from 2020 to 2026 for final synthesis where possible (Page et al., 2021; Savaiano & Hutkins, 2021) [24,33] . Landmark earlier works were considered eligible only when necessary to establish definitions, foundational mechanisms, or historically important evidence streams that remain central to interpretation (Savaiano & Hutkins, 2021) [33] . Search sensitivity was favored over excessive restriction during the initial stage because fermented dairy research is dispersed across dairy science, food chemistry, microbiology, nutrition, and clinical journals. However, during screening, preference was given to peer-reviewed journal articles with clear product characterization and explicit relevance to nutritional, microbiological, functional, or health-related endpoints (Saleem et al., 2024; Savaiano & Hutkins, 2021) [31,33] .

Inclusion and Exclusion Criteria

Studies were eligible for inclusion if they met all of the following criteria: • Published in peer-reviewed journals.

• Focused on fermented dairy products or clearly defined fermented milk matrices. [36,31,33] .

Priority was assigned to systematic reviews, authoritative narrative reviews, randomized controlled trials, prospective cohort studies, and landmark mechanistic investigations that directly informed interpretation of product functionality or health relevance (Savaiano & Hutkins, 2021) [33] . PRISMA 2020 guidance was used to support transparent documentation of selection logic and synthesis rationale (Page et al., 2021) [24] .

The following were excluded • Non-peer-reviewed publications, editorials without substantive synthesis, conference abstracts lacking full data, and non-verifiable reports.

• Studies on fermented non-dairy foods unless directly relevant as mechanistic comparators. • Articles in which the dairy product was insufficiently characterized or where fermentation status was unclear. • Publications making broad health claims without traceable primary evidence or adequate methodological description (Page et al., 2021) [24] .

These criteria were intentionally strict because the topic is vulnerable to overgeneralization. Fermented dairy products vary greatly in microbial ecology, processing history, and nutrient profile, so studies with poor product definition contribute disproportionately to interpretive noise (Saleem et al., 2024; Savaiano & Hutkins, 2021) [31,33] . [31,33] .

For reviews and human studies, particular attention was paid to the definition of the fermented dairy matrix, comparator choice, intervention duration, outcome specificity, and whether conclusions were based on observational associations, controlled interventions, or mechanistic reasoning. This distinction was necessary because the strongest claims in the field often depend on the quality of causal inference rather than on the number of positive studies alone (Savaiano & Hutkins, 2021) [33] .

Quality Assessment

Formal meta-analytic risk-of-bias tools were not applied across all included sources because this review is broader in scope and includes narrative reviews, systematic reviews, and mechanistic literature in addition to primary trials. Instead, quality was assessed narratively using principles consistent with PRISMA 2020 reporting transparency and with the evaluative approach reflected in the systematic review by Savaiano and Hutkins (2021) [33] , which differentiated favorable, neutral, and unfavorable findings while also considering study quality.

Greater interpretive weight was assigned to studies and reviews with the following features:

• Transparent search and screening methods.

• Clear identification of fermented dairy product type.

• Explicit microbial or starter culture characterization.

• Appropriate comparators.

• Clinically relevant endpoints.

• Cautious interpretation consistent with study design (Page et al., 2021; Savaiano & Hutkins, 2021) [24,33] .

Lower weight was assigned to studies with poorly defined products, inadequate controls, unsupported causal language, or claims extrapolated far beyond the underlying evidence base. This was especially important because recent narrative reviews, while often informative, sometimes aggregate wide-ranging health claims that are stronger in mechanistic plausibility than in direct clinical confirmation (Saleem et al., 2024; Pang et al., 2025) [31,25] .

PRISMA Flow Diagram

The review process followed the four broad PRISMA phases of identification, screening, eligibility, and inclusion, as recommended in the PRISMA 2020 update (Page et al., 2021) [24] .

• Identification: Records were sought from PubMed, Scopus, Web of Science, ScienceDirect, SpringerLink, Wiley Online Library, and Google Scholar using predefined keyword combinations related to fermented dairy products, microbiology, nutrition, and health outcomes (Page et al., 2021; Savaiano & Hutkins, 2021) [24,33] . • Screening: Duplicates were removed, after which titles and abstracts were screened for direct relevance to fermented dairy products and at least one predefined analytical domain, such as nutritional composition, bioactive compounds, microbial ecology, or health outcomes (Page et al., 2021) [24] . • Eligibility: Full texts were assessed for peer-review status, adequacy of product definition, methodological transparency, and relevance to the scope of the review. Articles lacking clear fermented dairy characterization, lacking sufficient methodological detail, or making unsupported claims were excluded at this stage (Page et al., 2021) [24] . • Inclusion: Final inclusion prioritized recent peerreviewed reviews and landmark primary studies needed to interpret current evidence on nutritional value, fermentation-derived bioactivity, and health effects, with particular weight assigned to systematic reviews and high-quality human evidence where available (Saleem et al., 2024; Savaiano & Hutkins, 2021) [31,33] .

Overview of Fermented Dairy Products

Fermented dairy products are obtained through the controlled action of microorganisms on milk or milkderived substrates, leading to acidification, biochemical remodeling, preservation, and sensory transformation. Contemporary reviews consistently define this category as including yogurt, cultured fermented milk, kefir, cheese, cultured buttermilk, and region-specific products such as dahi and lassi, although the degree of process standardization differs markedly across products and regions (Saleem et al., 2024; Savaiano & Hutkins, 2021) [31,33] . This definitional breadth is scientifically relevant because "fermented dairy products" are often grouped together in nutrition discourse even though they differ substantially in microbial ecology, texture, nutrient concentration, ripening dynamics, and likely physiological effects (Saleem et al.,

2024; Widyastuti et al., 2021) [31,38] . Fermented dairy products encompass a diverse range of products that differ in microbial composition, fermentation characteristics, nutritional attributes, and potential health benefits. A comparative overview of major fermented dairy products, their associated microorganisms, fermentation characteristics, key bioactive components, and reported health benefits is presented in Table 1. Yogurt remains the most standardized fermented milk, traditionally produced by the symbiotic thermophilic starter pair Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus. Its technological identity is relatively well defined compared with many other fermented dairy foods, which partly explains why yogurt dominates the evidence base for lactose digestion and broader health outcomes (Savaiano & Hutkins, 2021; Savaiano, 2014) [33,32] . By contrast, cultured fermented milks and traditional dahi-type products may vary in inoculum composition, fermentation temperature, solids content, and postfermentation handling, producing greater heterogeneity in both nutritional profile and biological interpretation (Saleem et al., 2024) [31] . Kefir occupies a distinct position because its fermentation often involves mixed bacterial and yeast communities rather than only conventional lactic starters. This mixed ecology generates a broader metabolic spectrum, including carbon dioxide, trace ethanol, organic acids, and exopolysaccharides, and may therefore produce functionality that is not directly comparable to yogurt (Saleem et al., 2024; Sibanda et al., 2024; Lim et al., 2026) [31, 37, 20] . At the same time, kefir research is complicated by product variability: grain-based artisanal kefir, industrial kefir-like beverages, and products made with defined starters are not microbiologically equivalent, yet they are sometimes treated as a single entity in review literature (Lim et al., 2026) [20] . Cheese constitutes an even broader class because fermentation is followed, in many varieties, by coagulation, whey drainage, salting, and ripening. As a result, cheeses represent fermented dairy matrices in which concentration effects, moisture loss, ripening microbiota, and proteolytic maturation strongly shape nutritional density and peptide generation, distinguishing them from fresh fermented milks (Saleem et al., 2024; Widyastuti et al., 2021) [31,38] . This distinction matters because nutritional comparisons between fermented and non-fermented dairy are more straightforward for yogurt versus milk than for ripened cheese versus fluid milk, where processing-induced concentration effects confound simple interpretation (Saleem et al., 2024) [31] . A recurring issue across the literature is overgeneralization of the category. Reviews increasingly present fermented dairy foods as functional foods, but the evidence does not support a uniform effect size or mechanism across all products (Saleem et [31,33,2] . The most defensible interpretation is therefore matrix-specific: fermentation is a unifying process, but the resulting foods differ enough that claims about digestibility, bioactive compound content, microbiome modulation, or health benefit must be interpreted by product type rather than by category label alone (Saleem et al., 2024; Savaiano & Hutkins, 2021) [31,33] .

Microbiology of Fermented Dairy Products

The microbiology of fermented dairy products is centered on lactic acid bacteria (LAB), whose primary technological functions include lactose metabolism, acidification, inhibition of undesirable microorganisms, textural development, and flavor generation. Recent reviews continue to identify LAB as the dominant microbial engine of dairy fermentation, with Streptococcus, Lactobacillus sensu lato, Lactococcus, Leuconostoc, and Bifidobacterium among the most relevant genera in cultured dairy systems (Saleem et al., 2024; Widyastuti et al., 2021) [31,38] . In yogurt, the classical association between Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus remains the core model of cooperative dairy fermentation. Their metabolic interaction accelerates acid production and contributes to flavor and texture formation, which is one reason yogurt is technologically robust and comparatively reproducible across industrial settings (Savaiano, 2014; Saleem et al., 2024) [32,31] . However, even within yogurt, product functionality is not determined solely by the classical starter pair. The addition of probiotic adjuncts such as Lactobacillus acidophilus, Lacticaseibacillus casei, Lacticaseibacillus rhamnosus, or bifidobacteria can change viability profiles, enzyme activity, metabolite formation, and possibly health outcomes, though these benefits remain strain-dependent and cannot be inferred from species names alone (Widyastuti et al., 2021; Savaiano & Hutkins, 2021) [38,33] . Kefir microbiology is more complex than yogurt microbiology because kefir grains or kefir-like cultures contain consortia of LAB, yeasts, and sometimes acetic acid bacteria. Reviews of kefir emphasize that these symbiotic communities may include Lactobacillus kefiranofaciens, Lentilactobacillus kefiri, Lactococcus lactis, Leuconostoc spp., and various yeasts, with community structure influenced by substrate, geography, and fermentation conditions (Sibanda et al., 2024; Lim et al., 2026) [37,20] . This complexity may expand the metabolic repertoire of the final product, but it also introduces a reproducibility challenge absent from more standardized fermented milks. In practice, the term "kefir" often covers products with very different microbial compositions, making cross-study comparison difficult unless microbial communities are explicitly characterized (Lim et al., 2026; Saleem et al., 2024) [20,31] . Across fermented dairy products, microbial activity contributes not only to fermentation itself but also to preservation. Acidification lowers pH and suppresses many spoilage and pathogenic organisms, while additional metabolites such as hydrogen peroxide, diacetyl, and bacteriocin-like substances may strengthen inhibitory effects, especially in model systems (Saleem et al., 2024; Widyastuti et al., 2021) [31,38] . Yet it is important to distinguish food preservation roles from direct human health claims: evidence for antimicrobial activity in the food matrix or in vitro does not automatically establish a clinically meaningful antimicrobial effect after consumption (Lee et al., 2026; Saleem et al., 2024). Another key issue is viability. Classical fermentation microbiology assumes that live cultures are important for product identity and some physiological effects, especially in yogurt and probiotic fermented milks. Historical and modern lactose-digestion studies support this position for yogurt because viable or at least enzyme-active cultures contribute β-galactosidase activity in the gastrointestinal tract (Martini et al., 1991; Savaiano, 2014; Savaiano & Hutkins, 2021) [21,32,33] . However, emerging reviews on postbiotics and fermentation-derived metabolites suggest that live-cell survival may not be the only route to functionality in fermented dairy, particularly for outcomes linked to bioactive peptides or non-viable microbial components (Arslan et al., 2026) [2] . This marks an important conceptual transition in the field: microbial viability remains critical for some claims, but not necessarily for all. Methodologically, dairy microbiology has also evolved. Culture-based enumeration remains useful for quality control, but molecular tools increasingly reveal that fermented dairy ecosystems are more dynamic than traditional counts suggest (Widyastuti et al., 2021) [38] . This is especially important for kefir, ripened cheeses, and multifunctional fermented dairy products, where ecological succession and subdominant taxa may influence flavor development and metabolite formation disproportionately relative to their abundance (Lim et al., 2026; Widyastuti et al., 2021) [20,38] . Future reviews and primary studies will need better culture-level and strain-level resolution if claims about fermentation-driven functionality are to be mechanistically precise.

Nutritional Composition of Fermented Dairy Products

Fermented dairy products retain the nutritional strengths of milk while modifying nutrient digestibility, bioaccessibility, and food structure through microbial activity. They remain important sources of high-quality protein, calcium, phosphorus, potassium, and vitamins, particularly in yogurt and cultured fermented milk (Saleem et al., 2024; Savaiano & Hutkins, 2021) [31,33] . Protein quality is a key advantage because fermentation partially hydrolyzes milk proteins, generating peptides and free amino acids that may enhance digestibility and contribute to flavor development (Choi, [7,27,26] . Although fermented dairy products are recognized as sources of bioactive peptides, evidence linking these compounds to specific clinical benefits remains limited (Korhonen, 2009; Choi, 2012; Peres et al., 2024) [18,7,27] . Lactose metabolism represents one of the most established nutritional benefits of fermentation. Active yogurt cultures provide microbial β-galactosidase, which improves lactose digestion and tolerance beyond the effect of lactose reduction alone (Savaiano, 2014; Martini et al., 1991; Savaiano et al., 1984) [32,21,35] . Studies further indicate that yogurt improves lactose digestion more consistently than some other cultured dairy products, highlighting the importance of product matrix, microbial viability, and enzyme activity (Savaiano et al., 1984; Savaiano & Illikoud et al., 2022). Fermented dairy products are also major dietary sources of calcium and phosphorus and may support bone health. Fermentation-derived phosphopeptides have been suggested to enhance mineral utilization, although evidence in humans remains limited (Park et al., 2015; Peres et al., 2024) [26,27] . The lipid fraction may also undergo fermentation-induced modifications, but the nutritional significance varies considerably among products such as yogurt, kefir, and cheese (Arslan et al., 2026; Saleem et al., 2024) [2,31] . In addition, microbial activity can influence vitamin content, particularly B-group vitamins, although these effects are highly strain-and product-dependent (Saleem et al., 2024; Arslan et al., 2026) [31,2] . Overall, fermented dairy products should be viewed as nutritionally modified food systems whose benefits depend on the specific product, microbial composition, and processing conditions.

6.

Bioactive Components Generated During Fermentation The generation of bioactive components during dairy fermentation is one of the strongest mechanistic arguments for considering fermented dairy products as functional foods. Fermentation activates microbial enzymes that hydrolyze proteins, remodel carbohydrates, generate organic acids, synthesize exopolysaccharides, and produce a range of low-molecular-weight metabolites that may influence product functionality and, in some cases, host physiology (Peres et al., 2024; Park et al., 2015; Arslan et al., 2026) [27,26,2] . However, the literature also shows a persistent gap between detection of bioactive molecules and proof of benefit in humans. [15,18,7,26,27] . While their biological activity is well established in vitro, evidence for consistent clinical benefits in humans remains limited due to uncertainties regarding bioavailability, stability, and doseresponse relationships (Peres et al., 2024; Arslan et al., 2026) [27,2] .

Exopolysaccharides

Exopolysaccharides (EPS) produced by lactic acid bacteria contribute significantly to the texture, viscosity, and waterholding capacity of fermented dairy products (Saleem et al., 2024; Arslan et al., 2026) [31,2] . Certain EPS, including kefiran, have also been associated with potential prebiotic and immunomodulatory properties (Lim et al., 2026) [20] . However, their technological importance is better established than their health benefits, which require further clinical validation (Arslan et al., 2026; Lim et al., 2026) [2,20] .

Organic Acids and Fermentation Metabolites

Fermentation generates organic acids such as lactic, acetic, citric, and succinic acids that contribute to acidification, preservation, flavor development, and inhibition of spoilage microorganisms (Saleem et al., 2024; Arslan et al., 2026) [31,2] . Fermentation also alters the metabolite profile of dairy products, potentially influencing antioxidant properties.

Nevertheless, evidence linking these metabolites to direct health benefits in humans remains limited (Arslan et al., 2026; Saleem et al., 2024) [2,31] .

Bacteriocins and Antimicrobial Compounds

Fermentation-associated microorganisms produce bacteriocins and other antimicrobial compounds that enhance product safety and shelf life by inhibiting spoilage and pathogenic microorganisms (Widyastuti et al., 2021; Saleem et al., 2024) [38,31] . Although their role in food preservation is well recognized, evidence supporting direct antimicrobial effects following human consumption is currently insufficient (Arslan et al., 2026) [2] .

Vitamins and Other Functional Compounds

Fermentation can modify vitamin profiles, particularly Bgroup vitamins, through microbial synthesis and metabolic activity (Saleem et al., 2024; Arslan et al., 2026) [31,2] . However, these effects are highly dependent on microbial strains, product formulation, and processing conditions. Consequently, fermented dairy products should be viewed as variable functional food systems rather than uniformly vitamin-enriched foods (Zhang et al., 2020) [39] . [33,6,2] . [5,8,37] . However, responses vary among individuals and products, indicating that benefits are not universal.

Gut Health

Modulation of Gut Microbiota

Evidence suggests that fermented dairy products can influence gut microbiota composition by increasing beneficial genera such as Lactobacillus and Bifidobacterium and, in some cases, enhancing microbial diversity (Chonnacháin et al., 2024; Sibanda et al., 2024; Bui et al., 2025) [8,37,6] . Nevertheless, the persistence and clinical significance of these changes remain uncertain (Gao et al., 2025) [13] .

Probiotic Effects

Fermented dairy products serve as effective carriers for probiotics due to their protective food matrix. Clinical studies have shown that specific probiotic fermented dairy products can reduce infectious disease incidence and improve gastrointestinal comfort, although benefits are strain-specific and product-dependent ( [28,11,33] . [12,28,16] .

Immunomodulatory Activity

Antioxidant Activity

Fermentation can generate peptides and metabolites with antioxidant properties, enhancing radical-scavenging and metal-chelating activities in vitro (Peres et al., 2024; Arslan et al., 2026) [27,2] . However, evidence linking these biochemical effects to meaningful reductions in oxidative stress in humans remains limited (Saleem et [31,17,2] .

Antimicrobial Activity

Lactic acid bacteria and other fermentation-associated microorganisms produce organic acids, bacteriocins, and antimicrobial metabolites that inhibit spoilage and pathogenic microorganisms, contributing to product safety and preservation (Widyastuti et al., 2021; Saleem et al., 2024; Kaur, 2022) [38,31,17] . Clinical evidence is limited, although probiotic fermented milk has shown benefits as an adjunct to Helicobacter pylori eradication therapy (Sachdeva et al., 2009) [30] .

Anti-inflammatory Effects

Several studies suggest that fermented dairy products may reduce inflammatory markers and support immune homeostasis. Meta-analyses have reported reductions in Creactive protein and favorable effects on selected immune biomarkers, although findings remain inconsistent across studies (Zhang et al., 2023; Bordoni et al., 2017) [40,5] . [9,23,33] . However, causal relationships require further confirmation through long-term intervention studies. [9,10,3,23] .

Metabolic Health

Cardiovascular Health

Bone Health

Fermented dairy products provide calcium, phosphorus, and high-quality proteins that support bone metabolism. Emerging evidence suggests potential benefits for bone health through improved mineral utilization, microbiota modulation, and reduced inflammation, although direct evidence for fracture prevention remains limited (Rizzoli et al., 2018; Bashir et al., 2025; Savaiano & Hutkins, 2021) [29,4,33] . [35,21,32,33] . This benefit is consistently supported by mechanistic and clinical evidence.

Lactose Intolerance Management

Potential Anticancer Effects

Epidemiological studies suggest that fermented dairy consumption may be associated with reduced risk of certain cancers, particularly colorectal cancer ( [39,19,14] . Proposed mechanisms include microbiota modulation, production of bioactive metabolites, and improved gut health. However, evidence remains largely observational, and definitive causal relationships have not been established (Savaiano & Hutkins, 2021) [33] .

Fermented Dairy Products and the Gut Microbiome

The gut microbiome provides one of the most coherent frameworks for explaining how fermented dairy products may influence host health, but it is also a field in which mechanistic sophistication currently exceeds clinical certainty. Fermented dairy foods can affect the intestinal ecosystem through several non-exclusive routes: delivery of live microbes, exposure to microbial cell components, provision of fermentation-derived metabolites, altered digestibility of the dairy matrix, and changes in substrate availability to resident microbes (Gao et al., 2025; Bui et al., 2025; Arslan et al., 2026) [13,6,2] . A central concept is that fermented dairy microbes may not need to colonize permanently to exert functional effects.

Transient passage through the gut may still alter luminal enzyme activity, interact with resident communities, or influence host epithelial and immune responses. This is particularly relevant to yogurt and probiotic fermented milks, where benefits such as improved lactose digestion or symptom relief can occur without durable microbial engraftment (Savaiano, 2014; Bordoni et al., 2017) [32,5] . Current evidence therefore supports a model of functional interaction rather than one of universal colonization. Short-chain fatty acids (SCFAs) are frequently invoked as mediators of gut-related benefits. Some human and animal studies report increases in fecal SCFAs after fermented dairy intake, and reviews increasingly discuss these metabolites as links between microbial fermentation, epithelial energy metabolism, mucosal integrity, and inflammatory regulation (Chonnacháin et al., 2024; Bui et al., 2025) [8,6] . Yet the evidence remains mixed: some studies report increases, others report decreases or no change, and SCFA measurements are not always coupled to clinical outcomes. As a result, SCFA modulation should be considered an emerging mechanistic pathway rather than a settled endpoint. [16,2,13] . The field is therefore moving toward a more precise "precision fermented dairy" framework in which specific products are evaluated as targeted modulators of gut ecology and host physiology rather than as generic healthy foods.

Overall, the microbiome literature supports a nuanced conclusion. Fermented dairy products can modulate the gut environment and, in some settings, the microbiota itself. However, the magnitude, and clinical meaning of these changes are highly context-dependent. The strongest current position is that microbiome modulation is an important explanatory mechanism for some fermented dairy effects, but it should not be treated as universal proof of benefit without corresponding human outcomes.

Technological Advances in Fermented Dairy Products

Technological advances have transformed fermented dairy products from traditional foods into platforms for delivering targeted health benefits and enhanced functionality. Probiotic fortification remains the most established approach, although maintaining microbial viability during processing and storage continues to be a major challenge. Increasing attention is also being given to postbioticenriched products, which offer improved stability and standardization compared with live probiotic formulations. Nevertheless, consumption patterns vary across regions due to cultural preferences, dietary habits, and familiarity with specific fermented products. Future consumer expectations are likely to emphasize health benefits, clean labels, sustainability, transparency, and sensory quality. Consequently, effective communication and strong scientific substantiation will remain critical for successful product development and market adoption.

Sustainability Aspects

The sustainability of fermented dairy products should be evaluated across environmental, economic, and social dimensions. Fermentation can enhance shelf life, reduce food waste, and increase the value of dairy products, thereby improving resource utilization. It may also support circular bioeconomy approaches through the valorization of dairy by-products and side streams. Economically, fermented dairy products represent important value-added foods with greater market differentiation and commercial potential (Afzaal et al., 2019) [1] . However, advanced functional formulations often require additional investments in strain selection, quality control, and product validation. From a social perspective, fermented dairy products contribute to nutrition security by providing high-quality protein, calcium, and other essential nutrients in forms that are often more digestible and culturally acceptable. Their established role in lactose intolerance management further enhances their public health relevance. Despite these advantages, sustainability benefits are not inherent to fermentation alone. Environmental impacts associated with milk production, processing, packaging, and refrigeration remain significant. Furthermore, successful commercialization depends on overcoming manufacturing challenges related to product stability, sensory quality, microbial viability, scalability, and cost-effectiveness. Therefore, the overall sustainability of fermented dairy products is highly dependent on production practices, technological efficiency, and consumer acceptance.

Future Perspectives

The future of fermented dairy products lies in the development of targeted, evidence-based foods designed to address individual nutritional and health needs. Advances in precision nutrition and microbiome science may enable Future research should prioritize large-scale clinical trials, standardized methodologies, multi-omics approaches, precision nutrition strategies, functional microbiome analyses, and sustainability assessments. Addressing these gaps will strengthen the evidence base and support the development of scientifically validated fermented dairy products.

Conclusion

Fermented dairy products represent a unique convergence of traditional food processing, microbial biotechnology, and modern nutrition science. Through fermentation, milk is transformed into nutrient-rich foods containing beneficial microorganisms, bioactive peptides, organic acids, exopolysaccharides, and other health-promoting compounds. Current evidence strongly supports their role in improving lactose digestion and gastrointestinal health, while emerging research suggests potential benefits for gut microbiota modulation, cardiometabolic health, bone health, and immune function. Recent advances in probiotics, postbiotics, synbiotics, precision fermentation, and microbiome-focused product development have further expanded the functional potential of fermented dairy foods. However, variability in product composition, microbial strains, processing conditions, and study methodologies highlights the need for greater standardization and robust clinical validation. Overall, fermented dairy products remain a scientifically promising and rapidly evolving area of food and nutrition research, with future progress expected to be driven by precision nutrition, multi-omics technologies, and well-designed human intervention studies that support the development of safe, effective, and sustainable functional foods.

Declaration of Competing Interest

The author declares no known competing financial interests or personal relationships that could have influenced the work reported in this manuscript.

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