Unveiling probiotic and prebiotic functional dairy foods: a health beneficial outlook

Abstract

Functional dairy foods represent a rapidly growing category in the food industry, driven by enormous consumer demand for health promotion and disease prevention. The interplay between probiotics and prebiotics in these products has the potential to enhance their overall health supports. Probiotics, such as Lactobacillus and Bifidobacterium species, commonly found in fermented dairy foods like yogurt, fermented milk, and whey beverages, support gut health by improving the intestinal homeostasis, that aids digestion, nutrient absorption, and strengthen the immune functionality. Meanwhile, prebiotics, naturally present in foods like chicory root, garlic, onions, and certain whole grains, serve as a nutritional source that promotes the growth of these probiotics. Synbiotics, the combined intake of probiotics and prebiotics, in functional dairy foods creates a synergistic effect, improving the survival and colonization of probiotics in the gut while amplifying their positive effects. It can trigger digestive health, reduce inflammation, and boost host immunity. Additionally, scientific research suggests that synbiotics offer benefits beyond gut health, including improved respiratory health and potential impacts on mental well-being through the gut–brain axis. Dairy products fortified with synbiotics provide a convenient and appealing way to incorporate these health-promoting components into the diet, making them increasingly popular in functional foods. Understanding the interactions between them, as well as the mechanisms behind their synergism, opens the door for developing innovative dairy products with enhanced nutraceutical potential.

Introduction

Global ecosystem encompasses human beings as an integral part requiring concise set of essential elements to meet fundamental necessities and attain a satisfactory quality of life (Miller et al. 2021). Food is one of those imperative components in human lives having implications in historical, societal, economic, political and ethical systems to shape identities, communities and ideological beliefs (Hamburg et al. 2014). This nutriment has been recognized by food science in bearing primary function of providing energy and nutrients as well as dealing with the regulation of the physical condition of the body (Betoret et al. 2011). However, nutrition which has been holding a paramount role in numerous traditional medicinal practices subsided significantly over the course of last century in curative medicines (Georgiou et al. 2011). This is attributed to changing lifestyle patterns, particularly poor dietary habits, and inadequate physical activities. Such changes have significantly contributed to the growing global burden of illness, including obesity, inflammatory and neurodegenerative disorders, diabetes, hypertension, atherosclerosis, cancer, and osteoporosis (Popa-Wagner et al. 2020). With due course of time, the increasing perception regarding the intimate bond between food and health in advanced societies significantly influenced food preferences by consumers opting for specific food items to attain particular health beneficial effects (Bogue et al. 2017). This consciousness and scientific association between specific food, disease and health has spurred a surge in research activities within the food industry to surface the concept of “functional foods” which is the intersection of two substantial facets i.e. dietary choices and healthy lifestyle (Henry 2010).

Functional foods flourished and accentuated with the renowned quote of Hippocrates “Let food be thy medicine and medicine be thy food” and his belief in the interconnectedness of medicine and food (Helal et al. 2019). However, the concept of functional food has evolved from the ancient Vedic texts from India and within the realm of Chinese traditional medicine. Further, the term was developed by Japanese researchers marking a decisive moment where the role of food surpassed mere nutrient supply and culinary enjoyment for human beings. This effective food made a remarkable dietary option formulated with an array of nutritional matrix enriched with appropriate products and bioactive components that can deliver enhanced health support beyond a part of general nutrition (Gul et al. 2016). Followingly, Japan adopted significant FOSHU-legislation (Foods of Specified Health Use) as one of the pioneer countries and introduced numerous health-enhancing products to the market (Galanakis 2021). The United States and European countries hold distinct definitions for these products, causing confusion among consumers, researchers, and professionals due to the absence of consensus. A team of European experts being a part of the Functional Food Science in Europe (FUFOSE) program, has outlined functional food as proven food items influencing specific bodily functions beyond their basic nutritional value as well as having significant role in lowering the risk of disease (Betoret et al. 2011). Nevertheless, functional foods are innovative food products intentionally crafted to incorporate substances or live microorganisms with potential health-boosting or illness-preventing properties (Temple 2022). Based on properties, American Dietetic Association bestowed functional foods as foods that can be unmodified/whole/conventional for instance; carrots with antioxidant β-carotene) and modified (fortified or enriched or enhanced with food components) (Hasler et al. 2009). The modified vitafoods have been designed to enhance quality of life by guarding against diet-related illnesses through elements such as dietary fibres, probiotics, prebiotic compounds, vitamins, flavonoids, polyols, soy protein, phenolic acids, fatty acids, essential oils and other valuable components (Díaz et al. 2020). The modifications in food have been categorized as improved by addition of a food component (non-vitamin antioxidant or prebiotic), removal of a constituent from food (allergen), increasing load of a naturally present constituent (fortification with a micronutrient to reach a dietary intake more than the recommended requirement), replacing a constituent (fats with modified starch) or modification of the bioavailability of a component in food (Shaikh 2022). Following health priorities and persistence of professionals in food and nutrition triggered collaboration with the food industry to introduce a remarkable array of new functional innovative food products as well as communicate allied health experts, government bodies, scientific community, and media to public about precise information and self-enlighten on functional foods (Dixit et al. 2023).

Among this realm of functional foods, milk and milk-derived products, specifically fermented foods, have been acknowledged to occupy a particular position in the human diet as they are efficient in providing nutritional adequacy and sustaining life during the period of growth and development (Ramchandran and Shah 2009; Tyagi et al. 2020; Jena and Choudhury 2023, 2024). Milk could potentially be classified as a functional food owing to its nutriments viz. casein, whey proteins, butyric acid, sphingolipids, calcium, conjugated linoleic acid (CLA), lactoferrin and lactoperoxidase (Patiño et al. 2013). In addition to the inherent nutritional benefits, dairy products such as milk, cream, yoghurt, kefir, powdered milk, condensed milk, butter, fermented dairy beverages, infant milk formula, colostrum, cheese, and ice creams have become some of the most widely consumed food items. They are recognized for their functional food potential through the inclusion of beneficial components such as probiotics, prebiotics, phytosterols, minerals, vitamins, and bioactive peptides (Martins et al. 2019). Furthermore, dating back to medieval times, humanity has long predicted the health dividends of these products thus, escalating scientific inquisitiveness in crafting functional dairy foods (Gulseven and Wohlgenant 2014). Functional dairy foods support escalating health benefits owing to antioxidant, cardioprotective, antihypertensive, immunomodulatory, antimicrobial, antidiabetic, anti-inflammatory and even for bone health protection (Davoodi et al. 2013). Considering this perspective, this review recapitulates to provide comprehensive understanding of the significance of functional dairy foods and their pivotal role in personalized health and well-being.

Functional dairy products

Probiotic dairy foods

Dairy sector is one of the largest among food processing industries where application of probiotics are uncovered in a plethora of products including fermented dairy products, butter/cream, ice cream and infant formula (Gao et al. 2021). Among the categorized foods, fermented dairy products have traditionally been interpreted as functional foods, as they are primary carriers for delivering health beneficial microbes (Ranadheera et al. 2017). Additionally, warranting the delivery of an adequate number of viable probiotic bacteria is essential for the health benefits of dairy foods, and the acclaimed minimum daily intake of probiotics is 6–9 Log CFU/g or mL or at least 8 Log CFU per serving (Hill et al. 2014; Terpou et al. 2019b). Yoghurt is one of the most popular and traditional fermented dairy products that has been consumed globally due to its nourishing value, healthcare benefits and sensory properties (Pachekrepapol et al. 2021). Conferring to the Codex Alimentarius Standard No. 243/2003, this specific product is made from milk fermented with “yoghurt cultures” consisting of Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus responsible for initiating characteristic flavour of yoghurt by glycolysis, proteolysis, and lipolysis (Dan et al. 2023). On the other hand, L. bulgaricus retains qualities that make it apposite as a probiotic, providing health benefits to its hosts (Oyeniran et al. 2020). The inclusion of L. delbrueckii subsp. bulgaricus KZM 2–11-3 and Lactiplantibacillus plantarum KC 5–12 as highly prospective production starter cultures have been reported with bioprotective and probiotic potential for production of healthy yoghurt (Hoxha et al. 2023). Irrespective of high protein, vitamins, and calcium constituents; fortification of yoghurt with fruits, vegetables, cereals, herbal extracts, essential oils, etc. not only intensified the quality characteristics and multifaceted health benefits, but also improved microstructure, colour and texture, microbiological properties, and biological activity (Rashwan et al. 2023). Furthermore, there has been copious evidences emphasized on these natural functional ingredients to be regarded as functional foods due to rich source of beneficial polyphenols and antioxidant capacity linked to holistic health effects (Fahmy et al. 2020; Hutsol et al. 2023). However, the comprehensive optimization in terms of type and concentration with different ingredients in production practices is indispensable to align with the specified objectives of fortification without compromising product quality (Ahmad et al. 2022).

The connection of probiotics and functional foods witnessed a global surge in probiotic functional yoghurt as a budding innovation in the dairy industry. Other than the inclusion of S. thermophilus and L. bulgaricus as starter cultures, there may be incorporation of other strains of lactic acid bacteria (LAB) known for their beneficial probiotic qualities in yoghurt-style products (Chang et al. 2021). Probiotic yoghurt with seven different combinations [C1 with yoghurt starter culture (YSC), T1 with YSC + Lactobacillus acidophilus (LA), T2 with YSC + Bifidobacterium bifidum (BB), T3 with YSC + L. plantarum (LP), T4 with YSC + Lactobacillus casei (LC), T5 with YSC + LA + BB and T6 with YSC + LP + LC] inferring multi species observed to be exerting more probiotic potential affecting nutritional, rheological and organoleptic properties (Soni et al. 2020). Similarly, probiotic yoghurt-like fermented milk product where inclusion of Lactobacillus desidiosus and Limosilactobacillus fermentum strains were observed to be more promising for maintaining the product quality throughout the storage period (Hossain et al. 2024). Overall, research finding discovered that binary probiotics could hypothetically kindle Lactobacillus brevis 54 to generate L-glutamic acid and pyruvic acid, thereby boosting the growth of the probiotics and their antioxidant capabilities (Fan et al. 2022). Furthermore, in connection with these studies, novel variants of yoghurt-based products supplemented with these fruits, vegetables, or herbs emerged with steady increase in the sales and popularity in the market upon consumer’s demand and sustainable development. Probiotic yoghurt containing up to 3% rice bran demonstrated improved antioxidant properties and improved growth of probiotic culture L. casei 431 (Demirci et al. 2017). Another novel functional probiotic yoghurt has been reported with Siraitia grosvenorii (monk fruit) fruit extract that exhibited strong antioxidant, ACE-I and antibacterial activities along with organoleptic properties (Abdel-Hamid et al. 2020). The addition of pineapple peel powder (PPP) to probiotic yoghurts containing Lactobacillus acidophilus (ATCC 4356), L. casei (ATCC 393), and Lactobacillus paracasei ssp. paracasei (ATCC BAA52) led to the release of antibacterial and anticancer bioactive peptides during refrigerated storage over 28 days at 4 °C. This resulted in enhanced antiproliferative and antibacterial activity in the PPP-fortified probiotic yoghurt compared to the control (Sah et al. 2016). A flavoured functional probiotic yoghurt has been revealed using Bifidobacterium longum strain and white sapote fruits pulp (WSP) at levels of 5, 10, and 15% in which 10% supplemented WSP received highest sensory acceptance (Khalil et al. 2022). Incorporation of passion fruit, banana, or apple peel powder has also contributed in augmenting the rheological properties and sustaining growth and development of probiotic culture in a probiotic yoghurt produced with L. acidophilus strains L10 and NCFM and Bifidobacterium animalis subsp. lactis strains Bl04 and B94 (do Espírito Santo et al., 2012; Espírito-Santo et al. 2013). Aloe vera as a promising herb has been fortified in a probiotic yoghurt containing L. acidophilus and B. bifidum where the bacterial count remains more than the suggested value (> 10⁹ CFU/ml) all through the storage period, thereby indicating its commercial sustenance (Panesar and Shinde 2011). Antioxidant properties and antioxidants maintenance throughout storage can be executed in probiotic yoghurt by effective addition of green, white, and black tea (Muniandy et al. 2016). Even though bovine milk has been conventionally preferred for yoghurt formulation, there has been a recent shift towards using goat and sheep milk due to their unique outstanding nutritional profiles for which the goat milk yoghurt has gained recognition as a functional food in healthcare (Ranadheera et al. 2018). In this context, a study addressed on goat milk yoghurt with addition of a probiotic L. acidophilus IIA—2B4 and roselle extract preceded towards formation of antimicrobial peptides in the product (Hanifah et al. 2016).

Whey, a by-product of cheese and paneer processing, has been acknowledged for its nutritional profile and a highly suitable ingredient propounding great applicability in the diverse food products (Deshmukh et al. 2024). This nutrient-rich byproduct attributed towards major environmental concerns due to its high levels of biological oxygen demand (> 30,000 ppm) and chemical oxygen demand (> 60,000 ppm) (Zhao et al. 2023). Conversely, the driving cause behind market growth and expanding demand for beverages enriched with vitamins, minerals, probiotics, prebiotics and antioxidants motivated food manufacturers towards whey addition in food formulations (Silva e Alves et al., 2018). Moreover, probiotic and prebiotic dairy-based beverages were midst of the pioneering functional dairy beverages commercialized in the market. A study formulated a fermented whey beverage to acquire low concentration of lactose and ß-lactoglobulin using L. acidophilus CRL 636, L. delbrueckii subsp. bulgaricus CRL 656, S. thermophilus CRL 804 and whey protein concentrate containing 35% of proteins (Pescuma et al. 2010). Further, a fruit-flavoured probiotic whey drink was manufactured using L. plantarum/L. brevis and different fruit concentrates of lemon, mango, pineapple, apple, or grape (Koç et al. 2013). Besides, whey proved to be a valuable substrate for production of kefir-like beverages (Mhir et al., 2019; Magalhães et al. 2010); the presence of inherent bioactive components in cultured buttermilk makes its beverages explored possessing therapeutic value (Mudgil et al. 2016). Likewise, innumerable ingredients termed as functional has been adopted for increased production of dairy-based probiotic foods acceptable from economic and technological perspective.

Prebiotic and synbiotic functional dairy foods

Prebiotics serving as another functional food component present significant technological advantages in large number of dairy food applications (Al-Sheraji et al. 2013). Diverse range of prebiotics such as galactooligosaccharides (GOS), inulin of different chain lengths, fructooligosaccharides (FOS), resistant starch and lactulose (Mazloomi et al. 2011; Delgado-Fernández et al. 2019) have been well recognised in the production of fermented milk products. An innovative functional cheese incorporated with FOS, as inulin and agave fructans as supplements exhibited valuable nutritional and functional attributes (Palatnik et al. 2019). Further, aloe vera polysaccharides possessing prebiotic potential has been proposed in a study where the authors produced a UF-soft cheese incorporated with aloe vera pulp at the levels of (5, 10, and 15 g/100 g) milk retentate and probiotic cultures for providing bioactive health effects in which 15% aloe vera pulp supplemented cheese displayed best sensory properties (El-Sayed and El-Sayed 2020). As ice cream is widely enjoyed across the globe, the incorporation of prebiotic ingredients can enhance its functional appeal. A study demonstrated that supplementing ice cream with galacto-oligosaccharides (GOS) improved its physicochemical properties and sensory qualities (Balthazar et al. 2015).

Further promotion of prebiotics is essential for the growth and reproduction of probiotics in the formulation of synbiotic dairy products. According to Swanson et al. (2020), a complementary synbiotic consists of a probiotic and a prebiotic that together offer one or more health benefits, without the need for a co-dependent function or linked effective doses. In contrast, a synergistic synbiotic includes a substrate specifically utilized by the co-administered live microorganisms. Hussien et al. (2022) observed that fortifying skim milk yoghurt with 2% inulin and FOS as prebiotics, along with a traditional starter culture including L. acidophilus and its bacteriocin, resulted in the best sensory profile during refrigerated storage. This formulation also extended the shelf life up to 39 days and effectively prevented fungal growth without affecting the development of the starter culture. Apart from inulin, lactulose-derived oligosaccharides has been considered as a functional prebiotic ingredient in comparison to conventional lactulose thereby, posing the benefit of maintaining adequate probiotic cell counts and initial level of prebiotic (Delgado-Fernández et al. 2020). The shelf-life of homemade yoghurt with sago starch oligosaccharides can be increased with positive functional effects in terms of good viable counts of LAB (Shima et al. 2012). Lentil polysaccharides has also been evaluated for their antioxidant potential in fuelling the growth of probiotic bacteria (L. acidophilus B-4495 and B. lactis 41,405) in yoghurt (Agil et al. 2013). In a study, milk supplemented with soy and pulse ingredients, particularly lentil and soy flour, enhanced the acidification rate of Lacticaseibacillus rhamnosus and L. acidophilus in probiotic yoghurt (Zare et al. 2012). Fouad et al., designed an experiment to create functional microcapsules by utilizing varying concentrations (1%, 3%, and 5%) of chickpea flour as a prebiotic source and probiotics, B. bifidum B-41410 and L. rhamnosus B-442 with sodium alginate as a coating material (W1/O/W2 double emulsion technique) (Fouad et al. 2022). The authors recorded highest value of protein, fat, ash contents and probiotics in microcapsules with 5% chickpea flour. The applicability of synbiotic microcapsules in the manufacture of functional stirred yoghurt fortified with xylooligosaccharides and L. acidophilus has been assessed along the storage period with noteworthy viability propagation (10.45 log CFU/mL after 20 days storage period) (Ismail et al. 2023). In a study conducted with low-calorie synbiotic yoghurt supplemented with inulin and oligofructose at 2%, the authors re ported in the improvement in viscosity, sensory, textural properties as well as in probiotic count (9.67 ± 0.02 log cfu/ml) (Chand et al. 2021). In another study, addition of inulin as a prebiotic to probiotic yoghurt enhances its functional properties and supports the viability of Bifidobacterium, while also extending the product’s shelf life (Kamel et al. 2021). Apple pomace has been proved as an effective functional and healthy dairy ingredient that produced firmer and more consistent gel structure without disrupting gelation in a set-type yoghurt (Wang et al. 2019). In a related study, Jovanović et al. (2020) enriched yoghurt with 1%, 3%, and 5% apple pomace flour (APF), a source of dietary fibre, polyphenols, and antioxidants, following inoculation with Lactobacillus acidophilus, Streptococcus thermophilus, and Bifidobacterium bifidum. The formulation containing 3% APF exhibited the highest values for firmness, cohesiveness, and viscosity index, along with the most favourable sensory profile. Further, a fibre-enriched acidophilus yoghurt has been assessed and optimized with 5% apple fibre encompassing desirable quality and sensory attributes (Issar et al. 2016). The impact of banana fibre and banana peel fibre at 0, 0.2, 0.5 and 1% concentrations in combination with L. casei and Lactobacillus gasseri on the chemical and rheological properties of camel milk-based synbiotic yoghurt has been studied (Safdari et al. 2021). They reported that these fibers effectively reduced yoghurt syneresis, one of its biggest disadvantages, while also contributing to improved health benefits. A research developed a functional product by incorporating a probiotic goat yoghurt with yacon flour (natural source of FOS) and analysed in a high-fat diet rodent model (Fabersani et al. 2018). The authors appraised the final product sustained the standards for the microbiological and physicochemical quality thus, demonstrating the potential of yacon flour as a prebiotic ingredient that led to increase the number of viable probiotic microorganisms in the food matrix. An investigation on fermented milk revealed that aloe vera gel powder positively influenced the survival of L. casei NCDC19 during storage. The probiotic showed the highest ACE inhibition activity (around 40%), and increasing the concentration of aloe vera pulp improved the product’s texture, including hardness, gumminess, and chewiness (Basannavar et al. 2014).

The functionalization of ice cream has been enhanced by fat and sugar substitution as well as supplementation with functional ingredients such as probiotics and additives (Genovese et al. 2022). In probiotic ice-cream; the influential factors to be pondered are probiotic attributes, type of milk and process parameters for maintenance of gut and oral microbial balance (Pimentel et al. 2021). Probiotic coffee ice cream formulated with concentrated coffee extract (CCE) and Bifidobacterium breve and L. plantarum demonstrated strong antioxidant and antimicrobial properties, leading to the conclusion that 3% CCE combined with probiotic bacteria can be effectively used to develop a functional ice cream that delivers a desirable coffee flavor and is rich in natural bioactive compounds such as phenols and vitamins (Shazly et al. 2022). Another study evaluated the survivability of three probiotic strains L. plantarum, L. casei and B. bifidum in ice cream using calcium alginate and whey protein concentrate microencapsulation with no substantial effect on the physiological properties and sensory score of ice cream (El-Sayed et al. 2015a). Sabet‐Sarvestani et al. (2021) reported FOS to improve the rheological properties of the ice creams and enhanced the viability of the L. casei and L. plantarum with higher antioxidant activity. Kowalczyk et al. (2022) reported that the addition of inulin to ice cream mix enhanced the survival rates of L. casei and Bifidobacterium BB-12. Furthermore, incorporating 4% apple fiber improved the viability of L. casei and L. paracasei, suggesting that sheep milk ice cream can serve as an effective matrix for delivering both probiotics and prebiotics. Research in dairy products using food production strategies will continuously be involved in producing more nutritious foods to cover the individual inevitabilities in sustainable and affordable processes. The details of the probiotic microorganisms, prebiotic fibres and their combination as synbiotics employed to develop functional dairy foods are discussed in Table 1.

Table 1.

A detailed list of probiotics and prebiotics used as functional food components in diversified dairy products

Dairy foods	Enriched functional components	References
Probiotic yoghurt	L. acidophilus LA5®, B. animalis subsp. lactis BB-12®	Lestari et al. 2022
	L. acidophilus LA5, L. rhamnosus LBA, B. animalis subsp. lactis BL-04	Saccaro et al. 2009
	L. plantarum VP-3.3, S. thermophilus	Rossi et al. 2021
	L. acidophilus	Akpoka and Obi 2019
	L. fermentum KU200060	Lim et al. 2020
Probiotic low-fat yoghurt	B. animalis	Dias et al. 2020
Fortified probiotic yoghurt	B. longum S9, L. acidophilus O16, L. acidophilus L-1, Whey protein hydrolysate	McComas and Gilliland 2006
	Saccharomyces boulardii CNCM I-745, Inulin	Sarwar et al. 2022
	L. plantarum ATCC 10241 microencapsulated with okra mucilage and sodium alginate	Seyed Saeed et al. 2023
	L. brevis B7, hydroponic ginseng	Song et al. 2021
	L. casei ATCC393, Sea buckthorn berries	Terpou et al. 2019a
	L. casei 431®, L. rhamnosus LGG®, B. subsp. lactis Bb-12®, fruit peel powder	Zahid et al. 2022
	soy milk, mango pulp 7.2%, B. bifidus, L. acidophilus	Ahluwalia and Kumar 2013
	B. bifidum, fennel seed extract	Atwaa et al. 2022
Probiotic goat milk yoghurt	L. acidophilus IIA-2B4, roselle extract	Wihansah et al. 2018
	S. boulardii	Karaolis et al. 2013
	Pistacia atlantica resin extracts, S. boulardii	Hadjimbei et al. 2019
Synbiotic goat milk yoghurt	Cupuassu pulp, L. acidophilus LA-5, Inulin	Costa et al. 2015
Flavoured fermented goat milk	Algae oil nanoemulsion using whey protein isolate and sodium caseinate, mandarin juice	Ibrahim et al. 2021
Fiber-enriched acidophilus yoghurt	L. acidophilus, B. longum, Dried apple pomace	Issar et al. 2016
Stirred probiotic fruit yoghurt	Fruit preparations mango, mixed berry, passion fruit and strawberry, L. acidophilus LAFTI® L10, B. animalis ssp. lactis LAFTI® B94	Kailasapathy et al. 2008
Probiotic set yoghurt	L. rhamnosus, Prickly pear fruit pulp 8%	Azeez Khalid Albayati et al. 2024
Synbiotic yoghurt	B. bifidum, B. animalis, B. lactis microencapsulation-Inulin	Fayed et al. 2019
	L. plantarum BL011 Microencapsulation-3% Alginate coated with chitosan	Brinques and Ayub 2011
	L. brevis PML1, Inulin 2.5%	Falah et al. 2021
	B. longum BB536, Xanthan gum	Khalid et al. 2022
Synbiotic cream cheese	B. animalis Bb-12, L. acidophilus La-5, inulin	Alves et al. 2012
Tomato flavoured cream cheese	L. paracasei Lpc-37	Santini et al. 2012
Probiotic cottage cheese	L. casei ATCC 373, L. rhamnosus GG ATCC 53103, Probiotic mix YO-MIX™ 205 L. bulgaricus, L. acidophilus, Bifidobacterium spp.	Abadía-García et al. 2013
Synbiotic fermented milk	L. acidophilus, L. rhamnosus, Bifidobacterium lactis, Inulin	De Souza Oliveira et al. 2011
	L. acidophilus CECT 903, L. casei CECT 475, B. bifidum CECT 870, Lemon and orange fibers	Sendra et al. 2008
	Lupin seeds oligosaccharides, B. lactis Bb-12, L. acidophilus La-5	Martínez-Villaluenga et al. 2006
	Probiotic lactobacilli, Inulin	Desai et al. 2006
Fortified ice-cream	Lycopene	Chernyshova et al. 2019
	Roasted date seeds	Khider et al. 2021
Probiotic goat milk ice-cream	B. animalis subsp. lactis BLC1	DaSilva et al. 2015
Probiotic/fortified ice-cream	L. acidophilus, L. rhamnosus, L. bulgaricus, B. lactis, binary co-cultures with S. thermophilus, inulin	De Souza Oliveira et al. 2011
	B. animalis Bb-12, L. acidophilus La-5	MagariÑOs et al. 2007
	L. acidophilus, B. lactis, L. paracasei subsp. paracasei	Haynes and Playne 2002
	L. acidophilus, B. bifidum	Hekmat and McMahon 1992
	L. acidophilus ATCC 4356	Arslan et al. 2016
	Saruç, grape seed, S. boulardii	Salik and Arslaner 2020
Synbiotic ice-cream	Inulin, L. casei 01	Balthazar et al. 2018
Synbiotic camel milk ice-cream	Black rice powder, L acidophilus LA-5	Elkot et al. 2022
Fortified dairy foods
Goat milk yoghurt	Jujube pulp	Feng et al. 2019
	2% beet root, 2% level of ginger extracts	Srivastava et al. 2015
Yoghurt	Red ginseng extract 2%	Park et al. 2018
	Aronia juice	Nguyen L and Hwang 2016
	Herbs Codonopsis pilosula, Illicium verum, Lycium barbarum, and Psidium guajava	Shori and Baba 2023
	Green olive powder	Cho et al. 2017
	Flaxseeds	Mousavi et al. 2019
	Argel leaf extract	Mohamed Ahmed et al. 2021
	Turmeric extract	Martina et al. 2020
	Moringa extract	Zhang et al. 2019
	Hibiscus sabdariffa L. flowers marmalade 20%	Arslaner et al. 2020
	Orange peel extract	Zaki et al. 2024
	Sweet orange	Al-Bedrani et al. 2019
	Whole soy bean flour	Amove J et al., 2019
	Nano-sized eggshell powder	El-Shibiny et al. 2018
	Date fiber	Hashim et al. 2009
Stirred type yoghurt/yoghurt drink	Apple pomace powder	Wang et al. 2020
Yoghurt-ice-cream	Inulin
Low fat yoghurt	Encapsulated echium oil	Zahran et al. 2021
Milk beverage	Kiwi pulp and sesame oil	El-Sayed et al., 2015b
	Cupuassu pulp, Flour	Gutiérrez-Álzate et al. 2023
Labneh	L. casei FEGY9973	El-Shafei et al. 2018
Functional whey beverages	Mango pulp, Mentha arvensis	Hiralal and Raj 2014
	Sweet whey, papaya pulp	Mohamed et al. 2014
	Chakka whey, pomegranate juice	Babar et al. 2008
	FOS	Yasmin et al. 2015b
	Concentrated whey, Prange juice	Chatterjee et al. 2015
	Chhana whey, Pineapple pulp	Bhavsagar et al. 2010
	Mango pulp, 10% Sugar and 0.1% CMC	Pandey and Ojha 2020
	Mango powder 20.0%, Flaxseed oil 0.5%, Pectin JMJ and monoglyceride 0.5%	Gad et al. 2013
Probiotic whey beverage	Grape juice, probiotic isolates	Idan et al. 2021
	Rennet whey, L. acidophilus LA-5, B. animalis ssp. lactis BB-12	Drgalic et al. 2005
	Chhana whey, Watermelon juice, L. acidophilus NIAI L-54	Begum et al. 2019
	Eggshell 1%, egg yolk 1%, CMC 0.1%, vanilla with sweet whey 0.01%, B. animalis ssp. lactis Bb-12, Date syrup 12.5%	Gab-Allah and Shehta 2020
	B. animalis subsp. lactis	DaSilva et al. 2018
	Pineapple juice, L. acidophilus	Shukla et al. 2013
	Pasteurized acai pulp 5%, B. longum BL 05, L. acidophilus La14	Zoellner et al. 2009
Fermented buttermilk beverage	Soursop pulp	Buddhadasa et al. 2015
	Pediococcus acidilactici BD16	Sharma et al. 2021

Health benefits and beyond

The health benefits connected with ingesting of probiotics, prebiotics and synbiotics labouring development of functionality in dairy foods for human health parameters are depicted in Fig. 1 and in detail discussed in the subsequent sections of this review.

Fig. 1.

Health beneficial effects of probiotics, prebiotics and synbiotics on various human health activities

Gastrointestinal health

Probiotic yoghurt appreciably contributes to human health by providing natural nutrients and enhancing gut microflora through probiotic LAB (Meybodi et al. 2020). Popovic et al., reported that yoghurt made with the novel indigenous strains S. thermophilus BGKMJ1-36 and L. bulgaricus BGVLJ1-21 enhanced gut health by interconnecting key processes that are crucial for maintaining epithelial homeostasis and strengthening gut barrier (Popovic et al. 2020). Fox et al. (2015) suggested that consumption of probiotic yoghurt (200 g/day) containing L. rhamnosus GG, B. lactis (Bb-12) and L. acidophilus (La-5) observed to be effective in reducing antibiotic-associated diarrhoea in 1–12 years age group children as compared to pasteurized yoghurt for same duration as their antibiotic treatment. Among digestive disorders, constipation is one of the major concern in pregnant women (Cullen and O’Donoghue 2007). A triple-blind randomized controlled trial was conducted on 60 constipated pregnant women fed with conventional yoghurt and probiotic yoghurt enriched with L. acidophilus (La-5) and B. lactis (Bb-12), where the authors observed in the improvement of the symptoms of constipation by consumption of 300 g/day probiotic and conventional yoghurt (Mirghafourvand et al. 2016). Synbiotic dietary supplements are considered an effective approach for managing constipation. Supplementation with synbiotic yoghurt containing konjac mannan oligosaccharides (KMOS) and B. animalis ssp. lactis BB12 was shown to enhance faecal excretion and reduce constipation in constipated Kunming mice (Li et al. 2021). Pereg et al., revealed a non-significant tendency towards lessening the occurrence of diarrhoea by consuming probiotic fermented yoghurt containing L. casei in healthy young adult participants (Pereg et al. 2005). An in vitro study conducted with probiotic herbal yoghurt consisting of L. acidophilus LA-5 and NCFM, Bifidobacterium Bb-12, L. casei LC-10 and herbs such as cinnamon and licorice inhibited the growth of Helicobacter pylori (Behrad et al. 2009). Synbiotic yoghurt containing B. lactis Bb12, L. acidophilus La5, L. casei CRL431 and inulin demonstrated reductions in energy intake irrespective of no significant measures in gastrointestinal transit time in 65 healthy Canadian adults (Tulk et al. 2013).

Fermented milk is one of the most commercial dairy products consumed due to its good health effects in several clinical syndromes (Saleem et al. 2024). In this context, this approach compelled manufacturers for production of probiotic fermented milk as fermented milk are suitable carrier of probiotics for improving health status (Khorshidian et al. 2020). In a study by Guyonnet et al., the authors illustrated that fermented milk enriched with B. lactis alleviated symptoms in women experiencing minor digestive disorders thereby, improving well-being of the gastrointestinal system (Guyonnet et al. 2009). A meta-analysis on probiotic fermented milk with B. lactis CNCM I-2494 and LAB improved gastrointestinal discomfort in the general adult (Eales et al. 2017). Waitzberg et al. discussed on improved gastrointestinal well-being upon consumption of probiotic fermented milk supplemented with B. lactis CNCM I-2494 by healthy women (Waitzberg et al. 2015). A study trial reported that fermented milk containing living B. animalis DN-173 010 improved colonic transit time in healthy volunteers (Bouvier et al. 2001). The valuable effects of a fermented milk containing B. animalis DN-173010 has been discussed on discomfort HRQoL score and bloating in constipation-predominant IBS, and on stool frequency in adult subjects with < 3 stools/week (Guyonnet et al. 2007). The use of fermented milk containing the same strain has also been reported to improve stool frequency over a 3-week period in functionally constipated children (Tabbers et al. 2009). Chatterjee et al., revealed the therapeutic potential of fermented milk and L. acidophilus LA-5 and B. lactis BB-12 for treating antibiotic associated diarrhoea (Chatterjee et al. 2013). In another study, lactose-free milk formula with viable B. lactis Bb12 and S. thermophilus TH4 fed to infant revealed no significant control on the duration of diarrhoea, however, reduced rotavirus shedding with higher concentration of B. lactis Bb12 (10⁹ CFU/g) was observed (Mao et al. 2008). Further, Bourrie et al., expounded that administration of Bifidobacterium as a supplement affects the infant gut microbiota by diminishing the abundance of bacteroides (Bourrie et al. 2016). In an animal study, fermented milk containing yoghurt cultures and B. lactis CNCM I-2494 proved to be effective in stabilizing intestinal epithelial barrier junctions and lessening stress-induced visceral hypersensitivity in rats (Agostini et al. 2012). A formulated synbiotic fermented milk containing L. acidophilus La-5, B. animalis ssp. lactis BB-12, S. thermophilus and dietary fibre (90% inulin, 10% oligofructose) was demonstrated in a randomized double-blind, placebo-controlled multicentric study with a short-term effect on the amount and proportion of La-5-like strains and B. animalis ssp. lactis in the individual adult faecal microbiome having IBS (Bogovič Matijašić et al. 2016). Since constant constipation is considered to be associated with skin problems, an open-label trial was conducted with healthy young women consuming daily synbiotic milk containing B. breve strain Yakult and GOS for 4 weeks. The authors revealed of preclusion of skin dryness with stimulation of defecation and decreased production of phenol by gut bacteria upon consumption of probiotic and prebiotic product (Mori et al. 2016). Ensuing milk proteins and whey protein isolates as a very confirming protective matrices for probiotics, a study investigated the efficient therapeutic effect of developed probiotic whey beverages using L. casei BL23 or by Propionibacterium freudenreichii CIRM-BIA138 in preventing mucositis (a painful inflammation of the mucous membranes lining of the digestive tract), induced by 5-Fluorouracil in BALB/c mice (Cordeiro et al. 2018).

Cardiovascular health

Hypertension, diabetes, and dyslipidaemia are significant risk factors for cardiovascular and cerebrovascular diseases, contributing to approximately one-third of all deaths in the industrialized world (Qiu et al. 2021). Dairy foods specifically fermented products and probiotics upholds a challenging aspect in the prevention and management of cardiometabolic diseases in terms of modifying the microbial and metabolic composition of gut microbiota (Companys et al. 2020). Additionally, the authors, in their systematic review of prospective cohort studies and randomized controlled trials, discussed the effectiveness of probiotic supplementation through dairy matrices. They also found that it led to a greater reduction in lipid biomarkers among hypercholesterolemic subjects compared to probiotic supplementation in capsule or powder forms. Devouring of probiotic yoghurt containing B. animalis subsp. lactis Bb12 and L. acidophilus La5 has been considered as an alternative preventive approach and treatment method to lessen HbA1c and inflammatory markers in type 2 diabetes mellitus (DM) patients in comparison to conventional yoghurt (Mohamadshahi et al. 2014). A meta-analysis review recommend that probiotic yoghurt as a promising option in reducing the risk of gestational DM in pregnant women (Tabatabaeizadeh and Tafazoli 2023). Similarly, consumption of probiotic yoghurt enriched with anthocyanin-rich extract from riceberry rice created a favourable effect in reducing postprandial plasma glucose and plasma MDA with improvement of plasma antioxidant status in healthy volunteers (Anuyahong et al. 2020). Yadav et al., investigated diet containing low fat probiotic Dahi notably delayed the onset of glucose intolerance, hyperglycaemia, hyperinsulinemia and dyslipidaemia in high fructose-induced diabetic rats (Yadav et al. 2007). However, a probiotic yoghurt containing L. acidophilus La5 and B. animalis subsp. lactis Bb12 did not improve cardiovascular risk factors in terms of blood pressure, heart rate or serum lipid concentrations in a randomized 6-week double-blinded, factorial, parallel study (Ivey et al. 2015). A systematic review and meta-analysis of randomized controlled trials discussed about the requirement of larger trials for beneficial verification of probiotic yoghurt or other probiotic fermented milk on glycaemic markers and glucose control in diabetic and obese patients (Barengolts et al. 2019). Miller et al., determined the efficacy of synbiotic yoghurt containing L. plantarum D13-4, L. rhamnosus D7-5, L. paracasei D3-5, L. plantarum D6-2, and L. rhamnosus D4-4 as probiotic cultures and sago starch as prebiotic on the development of type 2 DM in mice (Miller et al. 2021). The authors revealed that favourable modulation of the gut microbiome and diminished leaky gut and inflammation in the gut-liver-pancreas axis upon consumption of the product. Another study elucidated consumption of vitamin D‐fortified probiotic yoghurt as a promising approach in improving the anorectic hormone, glucagon‐like peptide‐1 in adults undergoing low‐calorie diet in a double‐blind randomized controlled trial (Hajipoor et al. 2022). In the findings of buffalo milk yoghurt supplemented with freeze-dried B. lactis Bb-12 or B. longum Bb-46, the authors observed a marked effect in lowering the plasma and liver lipids levels in rats (Abd El-Gawad et al. 2005). More recent data has been highlighted on global obesity epidemic associated with cardiovascular risk factors. A report emphasized on obese women consuming probiotic yoghurt developed positive consequences on lipid profiles and insulin sensitivity with negligible effects on weight loss in comparison to low fat conventional yoghurt (Madjd et al. 2016). Clinical trials with human participants have been conducted with yoghurt fortified with whey protein, calcium, vitamin D, prebiotic fibre and probiotic cultures that led to considerable diminution in body fat mass, body fat percentage and waist circumference (Mohammadi-Sartang et al. 2018).

High level of total serum cholesterol is generally deliberated to be a risk factor for coronary heart disease and atherosclerotic change in vessels (Jeong et al. 2018). Numerous clinical studies have reported in consumption of probiotic fermented milk associated with lowering serum cholesterol levels. A study explained the effects of milk fermented by B. longum strain BL1 on blood lipids in rats and humans which exhibited significant lowering of serum concentrations of total cholesterol, low density cholesterol (LDL) and triglycerides in comparison with control (acid milk) possessing unchangeable concentration in high density cholesterol (HDL) cholesterol (Xiao et al. 2003). Overall, a systematic review and meta-analysis of randomized controlled trials by Ziaei et al. suggested in reduction of serum TC and LDL cholesterol levels upon consumption of probiotic fermented milk products especially by men for ≥ 8 weeks (Ziaei et al. 2021). Furthermore, inclusion of prebiotics (2% lactulose) with B. lactis in fermented milk resulted in a 35% reduction in cholesterol levels with increase in enzymatic activity (Beitāne and Ciproviča, 2013). Makwana et al., evaluated the hypocholesterolaemic effect of the synbiotic fermented milk using L. helveticus MTCC 5463 and L. fermentum with corn-starch (3%) as a prebiotic in healthy adult Wistar rats and observed reduction in concentrations of serum cholesterol and LDL-C/HDL-C ratio (Makwana et al. 2021). Gut dysbiosis is linked to obesity and probiotics play a pivotal role in progression of obesity. A systematic review and meta-analysis of clinical trials reflected on management of obesity in adults upon consumption of probiotic fermented milk products by significant reduction in body weight and body mass index (Mohammadi et al. 2021). Fermented milk supplemented with L. fermentum NCDC 400, L. rhamnosus NCDC 610 and FOS provided notable reduction in oxidative stress markers in the plasma and liver as well as prevention of obesity in high fat diet-fed animals (Akram et al. 2022).

Besides fermented dairy products with probiotic functional ingredients such as ω−3 and probiotics conferring health beneficial efficacies, hypocholesterolaemic efficacy of whey drink supplemented with 1.5% FOS has been observed in lowering elevated total and LDL cholesterol levels and triglycerides and increasing HDL cholesterol in rats (Yasmin et al. 2015a). Functional probiotic cheese has been proposed as an excellent matrix for probiotic cultures to confer beneficial properties to host (Araujo et al. 2023). A randomized double-blind placebo-controlled pilot study with hypertensive patients reported that probiotic cheese made with L. plantarum TENSIA reduced body mass index and arterial blood pressure values (Sharafedtinov et al. 2013). Mohd Hasali et al., elucidated the effect of the probiotic cheese on high fat diet induced metabolic disease in mice and found reduced body weight gain and white adipose tissue mass with lowering of glucose intolerance, accumulation of hepatic fat and adipocyte hypertrophy (Mohd Hasali et al. 2024).

Immune modulation

Functional probiotic yoghurt besides possessing nutritional efficacies, researchers reported on advantageous immune-modulating effects for patients with serious primary immune system disorders making individuals more vulnerable to infections, autoimmune diseases, and sometimes even cancers. Lorea Baroja et al., presented a short-term consumption of yoghurt supplemented with probiotic strains of Lactobacillus strains GR-1 and L. reuteri RC-14 fostered a favourable anti-inflammatory response in the peripheral blood of irritable bowel disease patients (Lorea Baroja et al. 2007). Similarly, in another study, daily consumption of a probiotic yoghurt containing L. gasseri CECT5714 and Lactobacillus coryniformis CECT5711 for 3 months induce enhanced beneficial effects on innate and specific immune response parameters in allergic children (Martínez‐Cañavate et al., 2009). In corroboration to the formulated product with same probiotics, its consumption improved intestinal flora, triggered defence against gastrointestinal aggressions and infections both by inhibiting pathogen adhesion to intestinal mucins in healthy children (Lara-Villoslada et al. 2007). Linking to oxidative stress, there has been reduction of fasting blood glucose levels (P < 0.01) and HbA1 C (P < 0.05) upon consumption of probiotic yoghurt (L. acidophilus La5 and B. lactis Bb12), while increasing erythrocyte superoxide dismutase and glutathione peroxidase activities over and above overall antioxidant status (P < 0.05) in type-2 diabetic patients (Ejtahed et al. 2012). The findings of Mazani et al., demonstrated of regular intake of probiotic yoghurt acts as defence system against exhaustive exercise-inducing oxidative injury in young healthy females notably by modulation of matrix metalloproteinase 2, matrix metalloproteinase 9 with some inflammatory factors (Mazani et al. 2018). However, no significant differences have been observed on the plasma levels of antioxidant and oxidant parameters in young healthy women consuming both probiotic and conventional yoghurt (Fabian and Elmadfa, 2007). Currently, in agri-food sector, dairy products served as effective carriers for delivering phytochemicals/nutraceuticals in form of herbs or their extracts for nutritional purposes. A group of researchers studied the antioxidant capacity of probiotic yoghurt enriched with phenolic/polyphenolic extracts from riceberry rice in healthy volunteers (Anuyahong et al. 2020). It was observed that riceberry rice yogurt could be a healthy food for improving the postprandial glycaemic and antioxidant response in humans Similarly, efficacy of Nyctanthes arbor-tristis aqueous flower extract-fortified yoghurt observed to intensify functional characteristics and prevention of diet-driven glycation activity (Amadarshanie et al. 2022).

Students have been reported with suppressed immune response where consumption of fermented milk containing L. casei DN-114001 modulated the number of lymphocytes and CD56 cells in those university students under academic examination stress (Marcos et al. 2004). Probiotic fermented milk has also reported with gripping evidences upon amelioration of intestinal disorders. Supporting this claim, a randomized, controlled, double-blind nutritional intervention study using fermented milk reported to show a reduction in the pro-inflammatory cytokine TNF-α in mothers’ milk. Additionally, the study reported a decreased frequency of gastrointestinal episodes in breast-fed infants (Ortiz-Andrellucchi et al. 2008). The positive influence of a probiotic fermented milk has also been assessed in the immune status and haematological factors of Wistar rats. Wang et al., conducted at trial with synbiotic fermented milk containing B. lactis Bi-07, L. acidophilus NCFM and isomalt-oligosaccharide that enhanced intestinal health and exerted positive effect on the humoral and cell-mediated immunity in BALB/c mice (Wang et al. 2012). Application of kefir, a type of fermented milk amended oxidative stress and significantly inhibited hepatic inflammation in irradiated-induced rats (Ali et al. 2020).

Probiotic cheese supplemented with dairy Propionibacterium freudenreichii strain possessing techno-functional and probiotic criteria alleviated acute colitis through prevention in induction of local and systemic inflammatory markers as well as colon epithelial oxidative stress markers in mice induced by trinitrobenzene sulphonic acid (Plé et al. 2015). Further, Kim et al., reported the efficacy of probiotic cheese curd containing L. lactis LB1022 and L. plantarum LB1418 in alleviating hangovers by lowering blood alcohol and acetaldehyde concentrations as well as reducing alcohol-induced hepatic injury (Kim et al. 2023). Asoudeh et al. (2022) allocated probiotic cheese to 40 patients suffering from rheumatoid arthritis (RA) in a randomized, double-blind clinical trial study and hypothesized that intake of probiotic cheese might result in decreased inflammation and improvement in the gut microbiota. The role of gut microbiota in the pathogenesis of RA through fermented milk was supported with the collected evidences, particularly by the administration of L. casei as an adjuvant therapy through anti-inflammatory mechanisms (Ferro et al. 2021). These studies reflect that probiotics have direct influence on maintaining immune response to gastrointestinal consumption and further enhanced by presence of prebiotics formulations.

Effect on cancer

The consumption of fermented milk containing probiotic bacteria has also been suggested as a promising approach for cancer prevention, a disease recognized as one of the leading causes of death (Tasdemir and Sanlier 2020). Desrouillères et al., reported the potential role of fermented milk consisting L. acidophilus CL1285, L. casei LBC80R and L. rhamnosus CLR2) on prevention of colon carcinogenesis in rats treated with dimethylhydrazine (Desrouillères et al. 2015). Fermented milk containing probiotic L. helveticus R389 lessened the growth of breast tumors by reducing IL-6 and increasing IL-10 levels in serum, mammary glands and immune cells infiltrating the tumor (de Leblanc and Perdigon 2010). Cyclical administration of fermented milk with the similar strain diminished tumour growth and induced cellular apoptosis in a hormone-dependent breast cancer murine model (de LeBlanc et al., 2005). Lowered prevalence of colonic tumors and damage to the colonic mucosa as well as augmentation of IL-4 and IL-10 anti-inflammatory cytokines has been reported in a 10-week treatment on sodium sulphate induced colitis-associated colorectal cancer mouse model administered with synbiotic fermented milk containing L. gasseri 505 (LG) and Cudrania tricuspidata leaf extract (Oh et al. 2020). Abdelrazik et al., induced Ehrlich tumor by intraperitoneal injection with 1 × 10⁶ Ehrlich ascites tumor cells in mice and results highlighted that curcumin supplemented fermented milk containing L. plantarum EMCC 1027 enhanced antioxidant capacity and lowered pro-inflammatory mediators (Abdelrazik et al. 2023). Furthermore, to these studies, there has been improved IL-10(+) cells in mammary glands and decreased IL-6(+) cells in tumour upon administration of a fermented milk product, kefir, or kefir cell-free fraction (de LeBlanc et al., 2006). The intervention of synbiotic sheep milk ice-cream (L. casei 01 and inulin 10% wt./wt.) effects has been evaluated on carcinogen-induced male Swiss mice with lowering frequency of high-grade premalignant lesions in the colonic mucosa (Balthazar et al. 2021). This usage of probiotics, prebiotics, and their combinational synbiotics as natural agents proved to be therapeutic approach against colonic inflammation.

Respiratory tract infections

Respiratory system infections are an escalating concern in clinical medicine, and an increasing number of evidences highlight the importance of probiotic supplementation in promoting health and protecting against such infections. Notably, high-dose probiotic yoghurt containing B. animalis ssp. lactis Bb-12, Lactobacillus fermentum PL9988, L. plantarum SN35 N, L. acidophilus NCFM, and B. lactis Bi-07 was shown to enhance the response to respiratory viruses, including H1 N1 influenza and SARS-CoV-2, in mice and golden hamsters by increasing body weight and reducing inflammatory cytokine levels (Jeon et al. 2023). A study by Salarkia et al. (2013) reported reduction of upper respiratory tract (URT) infections with improved VO2 max along with reduction in ear pain in young adult female endurance swimmers following intake of probiotic yoghurt. Odintsova et al. (2021) fortified yoghurt with vitamins and probiotic Lacticaseibacillus and observed more improved effect on frequency and duration of URT infections in females consuming probiotic fortified yoghurt in comparison to placebo-consuming group. Apart from probiotic yoghurt, probiotic fermented milk with Lactobacillus GG reduced respiratory infections among aged 1–6-year aged day care children as day care centres and school are transmission places of common infectious diseases (Hatakka 2001). Similarly, fermented dairy product containing L. casei DN-114 001 has been associated with reduction in URT infections in elderly people (Guillemard et al. 2009). Moreover, meta-analysis on randomized controlled trials has revealed probiotic fermented dairy products intake as a potential dietary approach for the inhibition of infections in respiratory tract in all age groups probably, best probiotic combination and identified dosage needs to be tested in clinical trials (Rashidi et al. 2021; Picó-Monllor et al. 2021).

Mental health

Probiotics are often observed to be effective in modulating mental health by interacting with the gut–brain axis which have supportive impacts on central nervous systems, and termed as psychobiotics. Along with prebiotics they play a synergistic effect in controlling and reducing the risk mental disorders including depression, anxiety, autism, Schizophrenia, and Alzheimer’s (Bistas and Tabet 2023; Ansari et al. 2023). A single centre, randomized, controlled, parallel-arm design was studied with healthy women consuming fermented milk product containing B. animalis subsp lactis, S. thermophilus, L. bulgaricus and L. lactis subsp. lactis where the authors observed over a four-week period consumption impelled the activity of brain regions responsible for regulating the central processing of emotion and sensation (Tillisch et al. 2013). Similarly in a double-blind, placebo-controlled study with a probiotic combination (L. plantarum LP01, L. fermentum LF16, L. rhamnosus LR06, and B. longum BL04) for a duration of 6 weeks showed significant improvement in sleep quality in the probiotic supplementation group (Marotta et al. 2019). Supporting to these findings in a meta-analytic research study it was observed that probiotic supplements could be significantly effective in improving apparent sleep quality (Zagórska et al. 2020; Le Morvan de Sequeira et al., 2022). L. helveticus and B. longum were experimented in a double-blind, randomized clinical trial and it was observed to reduce anxiety-like behaviour in rats and lessening psychological pain in humans (Messaoudi et al. 2010). Nishikawa et al., reported the connotation of dietary prebiotics reduced risk of Alzheimer’s disease in a multiethnic population group (Nishikawa et al. 2021). Similarly, GOS supplementation lessened the neuroendocrine stress response and enhanced emotional attention in healthy volunteers after a period of 3 weeks (Schmidt et al. 2014). Overall, the probiotics promotes the mental health in multiple ways through the gut–brain axis regulating the central nervous system. The details of the probiotic, prebiotic and synbiotic formulations in different trial models and type of study with associated effects in human and animal models are deliberated in Table 2.

Table 2.

Depiction of health effects in human/animal models upon intake of functional dairy foods

Dairy foods	Health effects	Models	Type of study	References
Probiotic yoghurt	Improve fasting blood glucose, Antioxidant status	Diabetic human patients	Randomized, double-blind, controlled clinical trial	Ejtahed et al. 2012
	Management of non-alcoholic fatty liver disease NAFLD	Patients with NAFLD	Randomized clinical trial	Ebrahimi-Mousavi et al. 2022
	Decrease in LDL cholesterol	Healthy women	Randomized controlled trial	Fabian and Elmadfa 2006
	Control of glycaemic index	Diabetic adults	Randomized controlled trial	Mirjalili et al. 2023
	Increase in HDL cholesterol	Healthy female	Randomized trial	Sadrzadeh-Yeganeh et al. 2010
	Improve cellular immunity	Healthy young females	Randomized controlled trial	Meyer et al. 2006
	Reduction of IgE in plasma, Increase in regulatory T cells	Allergic children	Double-blinded, randomized, control comparative	Martínez‐Cañavate et al., 2009
	Reduction of HbA1c	Diabetic adults	Randomized, double-blind controlled clinical trial	Mohamadshahi et al. 2014
	Improve intestinal flora, Trigger defence against gastrointestinal infections	Healthy children	Randomized controlled trial	Lara-Villoslada et al. 2007
	Improved symptoms of constipation	Pregnant women	Triple-blind randomized controlled trial	Mirghafourvand et al. 2016
	Reduction risk of gestational DM	Pregnant women	Systematic review and meta-analysis	Tabatabaeizadeh and Tafazoli 2023
	Reduction of acute upper tract infections, Enhancement of T-cell-mediated natural immune defence	Respiratory tract infected adults	Randomized, blank-controlled, parallel-group design	Pu et al. 2017
	Modulation of metalloproteinase 2 MMP2, matrix metalloproteinase 9 MMP9 and inflammatory factors	Young females	Randomized controlled trial	Mazani et al. 2018
	Decreased high sensitivity C-reactive protein hs-CRP	Pregnant women	Randomized controlled trial	Asemi et al. 2011
	Maintenance of serum insulin levels	Pregnant women	Randomized controlled clinical trial,	Asemi et al. 2012
	Protection from acute URT infections	Middle-aged and elderly people	Randomized, blank-controlled, parallel-group	Pu et al. 2017
	Reduced chemotherapy related diarrhea	Cancer patients	Placebo-controlled randomized clinical trial with three-arm parallel groups	Mohebian F et al., 2023
	Lowered risk of inflammation	Patients with chronic kidney disease	Cohort study	Wagner et al. 2022
Probiotic cheese	Decreased inflammation	Adults	Randomized, double-blind clinical trial	Asoudeh et al. 2022
	Regulation of lipogenesis and inflammation in alcohol-induced liver injury	Rats	Pre-clinical study	Kim et al. 2023
Probiotic Dahi	Delayed onset of hyperglycemia, hyperinsulinemia, dyslipidemia	High fructose-induced diabetic rats	Pre-clinical study	Yadav et al. 2007
	Reduction in body weight, Reduction in blood glucose and plasma lipids	C57BL/6 mice	Pre-clinical study	Rather et al. 2014
Whey based beverages	Lowering cholesterol and triglyceride levels	Rats	Pre-clinical study	Yasmin et al. 2015a
	Prevention of weight loss and intestinal damages	Mice	Pre-clinical study	Cordeiro et al. 2018
Probiotic Fermented Milk	Improved colonic transit times	Healthy volunteers	Parallel double-blind study	Bouvier et al. 2001
	Improved discomfort and stool frequency	Constipation‐predominant IBS adults	Multicentre, randomized, double-blind, controlled trial	Guyonnet et al. 2007
	Improved gastrointestinal transit	Constipated patients	Single centre, randomized, double‐blind, controlled, parallel group study	Agrawal et al. 2008
	Modulation of immunological response	Lactating mothers	Randomised, controlled and double-blind with parallel groups	Ortiz-Andrellucchi et al. 2008
	Modulation of the number of lymphocytes and CD56 cells	Students	Clinical trial	Marcos et al. 2004
	Improved mood and cognition	Healthy members	Double-blind placebo-controlled trial	Benton et al. 2006
	Increased stool frequency	Adult females	Clinical trial	Yang et al. 2008
	Improved gastrointestinal discomfort	Adults	Double-blind randomized controlled trials	Eales et al. 2017
	Stimulation of immune system	Children	Prospective randomized, double-blind, placebo-controlled trial	Nocerino et al. 2017
	Prevention of antibiotic-associated diarrhea	Diarrheal patients	Prospective, randomized, double-blind, placebo-controlled study	Beausoleil et al. 2007
	Reduction in duration of winter infections	Elderly people	Randomised, controlled pilot study	Turchet et al. 2003
Fortified yoghurt	Improved body composition, Improved metabolic parameters	Males and Females	Randomized, double-blind study	Mohammadi-Sartang et al. 2018
Fermented buttermilk-based beverages	Lowering cholesterol and triacylglycerol concentrations	Young volunteers	Randomized controlled trial	Narkevičius et al. 2016
Synbiotic Yoghurt	Reduction in energy intake	Healthy adults	Randomized crossover double-blind study	Tulk et al. 2013
	Improved hepatic steatosis	Patients with NAFLD	Open-label, randomized controlled clinical trial	Bakhshimoghaddam et al. 2018
	Enhance immune response, Improvement in social and school functioning	School children	Clinical review	Mofid et al. 2019
Synbiotic fermented milk	Improved digestive health	Adults	Double-blind randomized controlled clinical trial	Liao et al. 2022
Kefir product	Inhibition of Ehrlich ascites carcinoma	Mice	Pre-clinical study	Badr El-Din et al. 2020
	Decreased insulin serum level	Type-2 diabetic patients	Randomized double-blind placebo-controlled clinical trial	Alihosseini 2017
	Subsided HbA1 C level	Diabetic patients	Randomized double-blind placebo-controlled clinical trial	Ostadrahimi et al. 2015
Koumiss	Enhanced intestinal immune function	Immunosuppressed rats	Experimental research study	Li et al. 2022
Probiotic fermented dairy drink	Increased specific antibody response to influenza vaccination	Adults	Randomised, multicentre, double-blind, controlled	Boge et al. 2009
	Decrease in rate of illness	Children	Double-blinded, randomized, placebo-controlled	Merenstein et al. 2010

Conclusions

Probiotics and prebiotics as functional constituents in dairy foods extends invigorating benefits for the overall public health well-being. Nevertheless, current obstacles include ensuring the stability and viability of probiotics through processing and storage, indulging in the complex interactions within the gut microbiome and individual variability in response to these foods led evolvement of regulatory frameworks for clear provision of guidelines and standards for these products. Moreover, the escalating awareness among health responsive population compelled demand for safe and sustainable ethical production practices as well as address the variability in individual responses towards identification of optimal strains and maximum efficient dosages of the functional components in much more clinical trials. Regardless of these challenges, the promising future of dairy based functional foods could lead to promotion of more effective and targeted probiotic and prebiotic formulations in the global market. In conclusion, it can be stated that the introduction of a new generation drugs based of targeted therapies employing probiotics, prebiotic and synbiotics can provide beneficial improvement of human health. However, conducting appropriate and rigorous research experimental plans are necessary to augment results to be applicable and beyond.

Author contributions

Rajashree Jena perceived the idea for the article, prepared and edited the final manuscript. Prasanta Kumar Choudhury prepared the figure, tables and edited the entire document. Prasanta Kumar Choudhury and Rajashree Jena help in final editing and contributed in developing the idea and critically reviewed the manuscript. All authors have read and agreed to the final draft of the developed manuscript for submission.

Funding

This research received no external funding.

Data availability

Data will be made available upon request.

Declarations

Conflicts of interest

The authors declare that they have no competing interests among them.