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Kefir and Health: A Contemporary PerspectiveZaheer Ahmed a , Yanping Wang b , Asif Ahmad c , Salman Tariq Khan d , Mehrun Nisa d ,Hajra Ahmad a & Asma Afreen aa Department of Home and Health Sciences, Faculty of Sciences, Allama Iqbal OpenUniversity, H-8, Islamabad, Pakistanb Tianjin Key Laboratory of Food Nutrition and Safety, Faculty of Food Engineering andBiotechnology, Tianjin, Chinac Department of Food Technology, University of Arid Agriculture, Rawalpindi, Pakistand Pharmaceutical Research Centre, P.C.S.I.R. Labs, Karachi, PakistanAccepted author version posted online: 03 Nov 2011.Version of record first published: 07 Feb2013.

To cite this article: Zaheer Ahmed , Yanping Wang , Asif Ahmad , Salman Tariq Khan , Mehrun Nisa , Hajra Ahmad & AsmaAfreen (2013): Kefir and Health: A Contemporary Perspective, Critical Reviews in Food Science and Nutrition, 53:5, 422-434

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Critical Reviews in Food Science and Nutrition, 53:422–434 (2013)Copyright C©© Taylor and Francis Group, LLCISSN: 1040-8398 / 1549-7852 onlineDOI: 10.1080/10408398.2010.540360

Kefir and Health: A ContemporaryPerspective

ZAHEER AHMED,1 YANPING WANG,2 ASIF AHMAD,3 SALMAN TARIQKHAN,4 MEHRUN NISA,4 HAJRA AHMAD,1 and ASMA AFREEN1

1Department of Home and Health Sciences, Faculty of Sciences, Allama Iqbal Open University, H-8, Islamabad, Pakistan2Tianjin Key Laboratory of Food Nutrition and Safety, Faculty of Food Engineering and Biotechnology, Tianjin, China3Department of Food Technology, University of Arid Agriculture, Rawalpindi, Pakistan4Pharmaceutical Research Centre, P.C.S.I.R. Labs, Karachi, Pakistan

Kefir and its related products are renowned nutraceutical dairy products produced through fermentation of yeasts andbacteria naturally present in grains of kefir. The nutritional attributes of this self-carbonated beverage are due to presenceof vital nutrients such as carbohydrates, proteins, minerals, vitamins, and some nutraceutical components. Antimicrobialactivity, better gut health, anticarcinogenic activity, control on serum glucose and cholesterol, control on lactose intoleranceand better immune system can be achieved through its regular consumption. Moreover, on the one side kefir is good dieteticbeverage, and of particular interest of athletes, and on the other side the whole kefir is good for feeding small babies andpre-schoolers for good tolerance against disease and quick weight gain. Lots of works have been done on kefir from ahealth point of view. This study summarizes all the data that have been compiled to date. The purpose of this review isto gather information about microbiological, chemical, nutritional, and therapeutic aspects of kefir and kefir-like productsto provide justification for its consumption. This review leads us to conclude that kefir begins a new dawn of food for themankind.

Keywords Kefir, health, nutrition, composition, therapeutic effects

1. INTRODUCTION

The use of probiotics has been known to mankind since cen-turies and quest for its health benefits is increasing in this cen-tury through focused research on various food products. For thispurpose, researchers have a growing interest in probiotics fromfermented milk products. Recent research over the last few yearsconcentrates on host-microbe interactions, modes of action, anddetoxification mechanisms that may influence the immune sys-tem in human or animal system (Zajsek and Gorsek, 2010). Con-sumers also showed their preference to find such foods whichare alternatives to conventional therapies during the treatment ofvarious chronic diseases. High consumer acceptance for theseproducts, industrial growth, high expenditures on health, needfor improved quality of life, aging process, and new productdevelopment are some important factors that may lead to thedevelopment of new nutritional and therapeutic cultured milksby the inclusion of natural kefir grains. The bioactive compo-nents and probiotics from fermented milk are considered rela-

Address correspondence to Zaheer Ahmed, Department of Home and HealthSciences, Faculty of Sciences, Allama Iqbal Open University, H-8, Islamabad,Pakistan. E-mail: zaheer 863@yahoo.com

tively safe as compared to other nutraceutical components fromother foods. Food products such as cultured fermented milk, ke-fir, yogurt, sauerkraut, kimchee, miso, natto, and cultured milkhave long been used due to their probiotics properties (Sarkar,2008; Zajsek and Gorsek, 2010). Among them kefir, that can betermed as yogurt of the 21st century (Gorski, 1994) has receivedconsiderable attention from food scientists because of its uniqueand complex probiotic properties.

Kefir is a fermented milk product having slight acidic taste,natural carbonation, and aroma. This type of fermented milkcontains a specific mixture of microflora that reside in symbi-otic manner in a carbohydrate polysaccharide matrix. The wordkefir is derived from Turkish language that means “feel good”having mixed lactic acid and ethanol producing microflora (Kur-mann, 1984; Jianzhong et al., 2009). This product is recog-nized as kephir, kefyr, kiaphur, kefer, kepi, knapon, and kippiin different areas. The major difference between kefir and othertraditional fermented milk originate due to presence of vari-able microflora that resides in a closed matrix system of ke-fir grains (Malbasa et al., 2009) and these microflora can alsobe isolated, propagated, and used for subsequent fermentationprocess. (Marshall and Cole, 1985). Kefir grains can be char-acterized as small cauliflower florets or cooked rice, having

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KEFIR AND HEALTH: A CONTEMPORARY PERSPECTIVE 423

Figure 1 Physical appearance of a typical kefir grain. (Figure available incolor online).

a length of 10–30 mm, irregularly shaped, white to yellow-ish in color, lobed, having firm texture and slimy appearance(Figure 1) (Loretan et al., 2003; Plessas et al.,2007). Thesegrains are good source of lactic acid bacteria, acetic acid bac-teria, and yeast cells that are embedded in a matrix of casein,complex sugars and mixture of polysaccharide. Other yeasts andbacteria that have been recognized in kefir grains are Leuconos-toc mesenteroides, L. helveticus, L. brevis, Lactobacillus plan-tarum, Lactobacillus kefiranofaciens, L. kefir, Kluyveromyceslactis, K. marxianus, Saccharomyces lipolytica, Kazachstaniaaerobia, and Pichia fermentans (Angulo et al., 1993; Lin et al.,1999; Wang et al., 2008, 2009, 2010; Magalhaes et al., 2010;Golowczyc et al., 2010; ). The microorganisms in kefir grainshave a capacity to produce weak organic acids, antibiotics, andnumerous types of bactericide; these substances have a lethaleffect on pathogenic microorganisms (Angulo et al., 1993).

Kefiran is an exopolysachhardie component of kefir that hassignificant importance in human health and nutrition and is rec-ognized in most of the regions on this globe such as Central Asia,Southwest Asia, Japan, the Middle East, North America, North-ern and Eastern parts of Europe, former USSR and North Africa(Koroleva, 1982; IDF, 1988; Otles and Cagindi, 2003; Piermariaet al., 2009). Especially in Soviet countries, kefir is being usedas prophylactic to lessen the threat of chronic diseases, and of-ten been suggested for healing gastrointestinal diseases, IHD,allergy, and hypertension (St-Onge et al., 2002; Farnworth andMainville, 2003). Kefir products also find acceptance for in-fants and preschoolers as mixed or artificial diet, (Ivanova et al.1980), in this context bifidokefir, containing Bifidobacterium bi-fidum is more effective than normal kefir in lowering infectionsof small intestine in young ones and infants (Murashova et al.,1997). Based on these health and nutritional claims kefir can beclassified as major probiotic resource (Yang et al., 2010).

2. CHEMICAL COMPOSITION OF KEFIR

The chemical nature of kefir and its reported therapeutic ef-fects are depicted in Table 1. Researchers observed great varia-tion in composition of fermented kefir products (Zubillaga et al.,2001), and most often these variation arises due to change insource and the fat content of milk, the nature of the grains or cul-tures and the process for manufacturing of kefir product (Kneifeland Mayer, 1991; Bottazzi et al., 1994). Similarly, greater vari-ation may appear in kefir grains. Kefir contains all of the im-portant nutrients. Moisture is predominant constituent (86.3%)followed by sugars, protein, ash, fats (Ozer and Ozer, 1999; LiutKevicius and Sarkinas, 2004), with minor amounts of alcoholand lactic acid (Webb et al., 1987). The carbon dioxide content infermented kefir product is dependent on kefir grain and increasesas the level of kefir grain increased in the product. The desiredcarbon dioxide concentration may be up to1.98 g/L with con-comitant production of alcohol in small amounts (Garrote et al.,2000; Beshkova et al., 2002). Other products formed during fer-mentation are lactic acid, acetic acid, pyruvic acid, hippuric acid,propionic acid, and butyric acid diacetyl and acet-aldehyde, thatare also adding some taste and aroma in the product (Zourariet al., 1988; Guzel-Seydim et al., 2000; Beshkova et al., 2002).Diacetyl and acetaldehyde, which are the major flavoring com-ponents, are produced by Str. Lactis subsp. diacetylactis andLeuconostoc sp. (Libudzisz and Piatkiewicz, 1990). Commer-cial kefir contains half as much ortic acid, twice as much pyruvicacid, nine times as much acetic acid, and about equal amount ofuric acid as found in commercial yogurt (Dousset and Caillet,1993).

Storage conditions affect the composition of kefir product.It has been observed that storage temperature at 48◦C may re-duce the ethanol, acetaldehyde, and acetoin concentration inthe product. However, diacetyl reduction was not noticed atthis temperature during storage (Klyavinya, 1980). Apprecia-ble amounts of vitamins, macro- and microelements were alsoobserved in kefir (Liut Kevicius and Sarkinas, 2004). Probiotickefir is considered fit for infants but with modified composi-tion. Klyavinya (1980) suggested that kefir intended for infantfeeding may contain appreciable amounts of fats (3.2–3.4%),solids-not-fats (8.0%) and sucrose (5.0%).

3. MICROBIOLOGICAL CHARACTERISTICS

Kefir has diversed and complex microflora predominantlyconsisting of defined and undefined species of yeast and bacte-ria and in varying amounts (IDF, 1991). The microbial compo-sition is variable and largely dependent on source (De Antoniet al., 2010). A symbiotic relationship was observed amongvarious microbial species in kefir grains (Margulis, 1995), andthis symbiotic nature offers some problems in identificationof constituent microorganisms within kefir grains. Abrahamand Antoni (1999) suggested higher microbial population for

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KEFIR AND HEALTH: A CONTEMPORARY PERSPECTIVE 425

fermentation process and it should be not less than 0.9% of theweight of wet kefir. Bacterial population in kefir ranged between6.4 × 104–8.5 × 108 cfu/g, and for yeasts this figure ranges be-tween 1.5 × 105–3.7 × 108 cfu/g (Witthuhn et al., 2004). Inaddition to these microbes, Irigoyen et al. (2005) showed thepresence of lactobacilli (108 cfu/ml), lactococci (105 cfu/ml),yeasts (106 cfu/ml), and acetic acid bacteria (106 cfu/ml) after24 hours of fermentation.

Several other researchers identified some other bacterialcultures that included species of Lactobacillus delbrueckiisubsp. delbrueckii, Lactobacillus Kefir, Lactococcus lactissubsp. Cremoris, Enterococcus faecalis, Lb. brevis, Lb. casei,Enterococcus faecium, Lactobacillus acidophilu, Streptococcusthermohilus, Lb. fermentum, Leuconostoc and Lactococcus andLactobacillus delbrueckii subsp. bulgaricus, (Wang et al., 2004;Witthuhn et al., 2004). Identified yeasts were Kluyveromyces,Zygosaccharomyces, Pichia, Torula, candida, and Saccha-romyces (Witthuhn et al., 2004; Golowczyc et al., 2008;Jianzhong et al., 2009; Wroblewska et al., 2009; De Antoniet al., 2010; Dimitrellou et al., 2010) Klyveromyces lactis,Klyveromyces matxianus and Saccharomyces cerevesiae asthe leading yeast microflora and Torulaspora delbrueckii,Zygosaccharomyces rouxii, Saccharomyces unisporus,Zygosaccharomyces rouxii, Debaryomyces hansenii and Toru-laspora delbrus were also found in small number of samples(Loretan et al., 2003).

4. NUTRITIONAL COMPOSITION

Apart from basic nutrients of kefir, high levels of aminoacids, proteins, phosphorus, and calcium are also observed inkefir. In this reference, it has been recognized a healthy foodproduct especially in the areas where it is consumed as staplefood (Vinderola et al., 2004). The higher nutritional value ofkefir (Table 1) is attributed to the presence of balanced chemi-cal substances such as protein, minerals, and vitamins, and thefermentation process may result in a significant increase in itsnutritional profile. Some important aspects on nutritional im-portance are summarized as follows.

4.1. Vitamin Content

Some researchers are of the view that during kefir fermen-tation process vitamins such as pyridoxine, vitamin B12, folicacid, and biotin are produced in higher amount whereas a declinein thiamine and riboflavin may occur during kefir fermentation(Kneifel and Mayer, 1991, Liut Kevicius and Sarkinas, 2004).Other researchers, while measuring the quantity of vitamins inkefir, showed a decline in vitamin B12 (Guzel-Seydim et al.,2000). This decline may be dependent to choice of specificmicroflora that may be present in the kefir grain (Roczniakovaet al., 1974). Commercially available kefir grains also tend to in-crease folic acid content of the product after fermentation (Alm,1982). Besides vitamin B-complex, kefir also contains apprecia-

ble amount of vitamin K (Otles and Cagindi, 2003) and vitaminC (Khamnaeva et al., 2000). Thus type of milk and supplement-ing microflora are the two decisive factors that may predict thequantity of vitamins in the product. Inclusion of Propionibac-terium pituitosum and Propionibacterium peterssoni resulted ina linear decrease in vitamin B12 (34–37%) (Roczniakova et al.,1974) whereas a sharp increase in folic acid (500%) and minorraise in pantothenic acid and vitamin B6 was observed whenPropionibacterium freudenreichii was incorporated during fer-mentation process (Cerna and Hrabova, 1982).

4.2. Protein Content

The knowledge about detailed protein profile of kefir grainis still under investigation and only limited information is avail-able (Abraham and Antoni, 1999). Apart from protein profile ofkefir grain, it is a well-accepted fact that when these grains wereused for culturing in whey (Fil Chakova and Koroleva, 1997)or in soymilk (Abraham and Antoni, 1999), these increased theprotein content of the final product. Whole milk, when used asa source, showed comparatively less protein content as com-pared to soymilk and whey (Fil Chakova and Koroleva, 1997;Abraham and Antoni, 1999). Proteolytic activity was alsodemonstrated by some scientists in kefir (Yuksekdag et al.,2004a) due to presence of lactococci (Otles and Cagindi, 2003;Yuksekdag et al., 2004a). Higher amounts glutamic acid andthreonine was reported in bifidokefir containing 2 × 107 cfu/mLbifidobacteria as compared to normal kefir (Molokeev et al.,1998). Fermentation process also enhances the ammonia, ser-ine, lysine, alanine, and threonine in kefir (Guzel-Seydim et al.,2003). Some other scientists reported the presence of trypto-phan, valine, lysine, methionine, phenylalanine, threonine, andisoleucine in fermented kefir (Liut Kevicius and Sarkinas, 2004).

4.3. Sugar Contents

A typical kefir contains 6% sugar (Ozer and Ozer, 1999),a major portion of the gelatinous matrix containing kefirmicroflora. Sugar present in kefir is known as kefiran, aheteropolysaccharide, which is glucogalactan in nature. Kefiranimproves gel formation, rheology, and viscoelastic characteris-tics in gels produced by acidified milks (Rimada and Abraham,2006) and forms gels at low temperatures. Kefiran had beenreported to form films isolated from LAB with low water vaporpermeability and extraordinary flexibility, even higher thanthose corresponding to low density polyethylene (Piermariaet al., 2009). In addition, polysaccharides of kefir have anumber of health endorsing characteristics such as inhibitoryeffects on rotavirus (Song et al., 2007), immunomodulation orepithelium protection.

4.4. Mineral Content

A significant amount of both major and minor minerals wasreported in kefir. These minerals include calcium, potassium,

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426 Z. AHMED ET AL.

phosphorus, magnesium, and micro-elements such as zinc, cop-per, manganese, iron, molybdenum, and cobalt (Liut Keviciusand Sarkinas, 2004).

5. THERAPEUTIC CHARACTERISTICS

Therapeutic characteristics of kefir due to presence of dif-ferent components are briefly described in Table 1, and arediscussed in the following sections.

5.1. Anticarcinogenic Effect

Epidemiological studies have showed that intake of fer-mented milk products may lessen the risk of onset of breastcancer in women (Reddy et al., 1983; Veeret al., 1989). Thisreduced risk of breast cancer may be attributed to the presenceof certain bioactive components in fermented milk that mayinclude certain proteins and small peptides. Their antitumori-genic activities have been confirmed by feeding trials on animalmodels both in cancer and in cultured tumor cells (Svenssonet al., 1999). These bioactive components have the capacity toprevent the cancer initiation; these also work by suppressing theinitiated tumor growth by hindering certain enzymes so that con-version of procarcinogen to carcinogen is eliminated. The othermechanism by which cancer initiation process slows down isthe activation of the immune system (Kneating, 1985). Anticar-cinogenic effect of kefir and kefir extract has been studied ex-tensively. Several other workers also reported encouraging dataabout antitumor activities of kefir in animal models, but this timethis antitumor activity may be due to presence of some polysac-charides in kefir extracts (Shiomi et al., 1982; Furukawa et al.,1990; Kubo et al., 1992; Cevikbas et al., 1994). In a planned ex-periment, in which mice were artificially transplanted with solidtumors of E-ascites carcinoma, an oral dose of 100 or 500 mg/kgof kefir resulted in a major decrease in tumor size by activatingthe immunosuppressive action in spleen (Kubo et al., 1992).Antimutagenic role of microflora in kefir is an established fact.Isolated strains of Lactobacillus, Streptococcus, Leuconostoc(Hosono et al., 1990) and Streptococcus lactis subsp. cremoris(Miyamoto et al., 1991) from kefir have a capacity to bind mu-tagens. Consumption of 2 g/day kefir product for a period ofnine days is more beneficial as compared to yogurt to lowerthe chance of tumor (Furukawa et al., 1990) but soy-milk kefirhas proved the best among all of these (Liu et al., 2002). Kefi-ran, which is a water-soluble glucogalactan, either isolated fromkefir grain or produced by L. kefiranofaciens, a strain isolatedfrom kefir (Wang et al., 2008), also have antitumor activity.However, during comparison study about water soluble and in-soluble polysaccharides in kefir, water-soluble polysaccharidesappeared more effective for suppression of tumors (Furukawaet al., 2000) and their effectiveness against tumors also im-proved at higher dosage level (Murofushi et al., 1983). Apartfrom nature and dosage of polysaccharides, antitumor activity

is also dependent on type of microrganisms during fermentation(Liu et al., 2002) especially Lactobacillus plays an importantrole (Santos et al., 2003). Another important nutrient that hasa role in anticarcinogenic activity is the protein. Guzel-Seydimet al. (2003) also revealed the idea that milk proteins especiallysulfur containing amino acid, play a major role to provide an-ticarcinogenic activity in kefir and alike products. Involvementof immune cells in the antitumor effect of kefir in a murinebreast cancer model was first time reported by De Moreno DeLeblanc et al. (2007). In such model, immune response in mam-mary gland played an important role to avoid tumor growth.Chances of estrogen-dependent human breast cancer cells canalso be minimized by the use of kefir extract (Chen et al., 2007).Initial stages of kefir mother culture and the final product ofkefir both showed encouraging results for antiproliferative ac-tivity against breast cancer cells. Very little is known about thesebioactive components having role as remedy for breast cancer.Still there is great potential to explore these bioactive compo-nent(s) along with the system by which these compounds acton cancerous cells. But there are sufficient evidences that newpeptides developed during fermentation process have a capacityto curtail growth of cancer cells (Chen et al., 2007; De MorenoDe Leblanc et al., 2007). Figure 2 exhibits proposed sites andmodes of action of kefir throughout tumor cycle.

5.2. Antibacterial Spectrum∗∗∗

Several researchers previously claimed the ability of someLactobacilli for production of antimicrobial compounds. Thisantimicrobial property may be attributed to the presence of hy-drogen peroxide, peptides (bacteriocins), ethanol, carbon diox-ide, diacetyl, and organic acids (lactic and acetic acids). Theseall substances serve towards preservation of food products andreduction in foodborne pathogens, food production, and stor-age. These also exhibit some nutraceutical effects by prevent-ing of gastrointestinal disorders and vaginal infections (Zamfiret al., 1999; Liu et al., 2008; Zhou et al., 2008; Simova et al.,2009). Kefir also contains inherited properties of milk in ad-dition to advantageous factors produced by microflora duringfermentation. These beneficial components of kefir inhibit thepathogens by primary and secondary metabolites such as smallpeptides, diacetyls, and organic acids produced by kefir mi-croflora (Golowczyc et al., 2008). In general, kefir has got bac-teriostatic effect on Gram-negative organisms but a better bac-tericidal effect against Gram-positive organisms was reported(Czamanski et al., 2004). The killing action of kefir againstListeria monocytogenes, Yersinia enterocolitica, Escherichiacoli (Gulmez and Guven, 2003), Listeria innocua (Morganet al., 2000), Salmonella enteritidis (Czamanski et al., 2004;Golowczyc et al., 2007), and Staphylococcus aureus, Bacilluscereus, Salmonella enteritidis, Listeria monocytogenes (ATCC7644), and E. coli (ATCC 8739) has been revealed (Ulusoyet al., 2007). Silva et al. (2009) reported the consequences ofantimicrobial activity of broth (added with different sugars) with

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KEFIR AND HEALTH: A CONTEMPORARY PERSPECTIVE 427

Figure 2 Tumor formation in body and proposed sites of action of kefir. (Figure available in color online).

kefir grains and it was noted that kefir grains hydrolyze the non-reducing sugars, which later on converted into organic acidsand some inhibitory substances having anti-pathogenic activity.The inhibited species included: Staphylococcus aureus, Can-dida albicans, Shigella sonnei, Escherichia coli, Salmonella ty-phi, Streptococcus pyrogenes and Candida albicans (Rodrigueset al., 2005a; Silva et al., 2009). Isolated lactobacilli from kefirshowed antagonistic behavior and several strains of from ke-fir grains in this regard were revealed by several researchers;these were effective against L. monocytogenes (28/58 strains),E. coli (43/58 strains), S. enteritidis (22/58 strains), Salmonellatyphimurium (10/58 strains), Shigella flexneri (36/58 strains)and Y. enterocolitica (47/58 strains) (Santos et al., 2003, Cza-manski et al.,2004; Yuksekdag et al., 2004b). In another experi-ment when strains of L. lactis, Lactococcus cremoris, S. Duransand S. thermophilus were isolated from kefir, these strains wereable to restrict the life of S. aureus, E. coli, and Pseudomonasaeruginosa (Yuksekdag et al., 2004b). A strain of Streptococcusthermophilus showed antagonistic activity against P. aeruginosa(Witthuhn et al., 2004). Degree of fermentation also affects theantibacterial activity of kefir. The growth of Listeria monocyto-genes and Yersinia enterocolitica showed increased populationin a single day but E. coli showed an increasing trend afterfermented period of two days (Gulmez and Guven, 2003). An-tibodies produced in kefir also showed the antibacterial activityagainst various pathogens (Koroleva, 1988). This bactericidaleffect by acetic acid bacteria and yeasts may be attributed toactivity of undissociated acetic and lactic acid (Garrote et al.,1998) or H2O2 formed by LAB is equally important for suchdiminishing effect (Yuksekdag et al., 2004a; Yuksekdag et al.,2004b).

5.3. Effect on Immune System

There is a direct link between nutrition and immune system(Vinderola et al., 2006a). Numerous citations have indicated

that fermented products prodeuced by LAB have a potentialin improving specific or nonspecific immune responses bothin animals and human models (Gill 1998; Matar et al., 2001;Perdigon et al., 2001; Isolauri et al., 2004; Vinderola et al.,2004). These probiotic microorganisms have two-way actions,either by perpetuating live microbial cells directly or may bringabout valuable properties indirectly through their secondarymetabolites that may act as biogenic compounds. Biogenicsare beneficial food components that originate from metabolicactivities of microflora and have some significance in relationto health without using microbial activity of native intestinalbacteria (Takano, 2002), while irregularity in functioning of gutmicroflora may result in generation of wide range of diseases(Mai and Draganov, 2009).

Kefir is widely believed to have an immunomodulatory andprodigestive effect (Jianzhong et al., 2009). Vinderola et al.(2005a) established the immunomodulating characteristics offermented kefir in a murine model, by demonstrating that doseand cell viability may effect Th2 or Th1 response. By consum-ing kefir, pulmonary and peritoneal macrophages can reducethe pathogenic activity thus affecting the mucosal response atvarious regions in the body. Such microflora also alter the re-sponse for cytokines that are non-native to host bacteria, thusmodifying the innate immunity. Kefir microflora also inducedthe production of IL-10 producing cells among adherent cellsderived from Peyer’s patches of mice (Vinderola et al., 2006a).In the most recent study, the immunomodulating capacity inmurine model explained the importance of dairy-based productsincluding kefir microflora on intestinal health. In this context,Vinderola et al. (2006b) observed that the kefir milk productsand fermented dairy products have a capacity to induce powerfulmucosal response for boosting immunity thus maintaining thehomeostasis in intestine. As a result of this, IgA production en-hances in both large and small intestine (Vinderola et al., 2006b).An elevated anti-cholera toxin (CT) IgA response was observedas compared to controls when kefir was fed to young and oldrats (6–26 months); that was due to enhanced mucosal immune

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response. Total nonspecific IgG blood levels increased in bothyoung and old rats, with a decreased level of IgG responseagainst anticholera toxin (Troreux and Schmucker, 2001). Exo-ploysaccharides produced by kefir microflora may also stimulatethe immune system in a similar fashion (Murofushiet al., 1983).In a study La Riviere et al. (1967) extracted kefiran from kefirgrains to develop a water-soluble polysaccharide fraction to beused as feeding material in mice experiments. This resulted inreduction of tumor expansion through cell-mediated immuneresponse. Furukawa et al. (1992) also believe in effectiveness ofwater-soluble fraction of kefir grains for enhancing immune re-sponse. It was found that the exopolysaccharide have a capacityto control gut mucosal response for induced protective immunitythus enabling the internal maintenance of intestinal homeostasisfor increased IgA production and influencing the systemic im-munity through the cytokines released to the circulating blood(Vinderola et al.,2006c).

Two determinants, i.e, health of host and stage of tumorgrowth, are important for determining whether the exopolysac-charides will boost the immune system or not. When Peyer’sPatch (PP) cells from tumor-bearing mice was incubated withkefir grain polysaccharides, it was observed that supernatant ofthis mixture increased the propagation of splenocytes (Furukawaet al., 1996).

5.4. Anti-Inflammatory

There are evidences that kefir and its polysaccharide ex-tract possess anti-inflammatory activity. In some organismskefir show anti-inflammatory properties by inhibiting the for-mation of granuloma tissue (Rodrigues et al., 2005b). Kefiralong with other substances exhibits varying degree of anti-inflammatory activity, in suspensions with molasses, fermentedmilk and kefiran extract presented an inhibition of 41, 44, and34%, respectively, for the inflammatory process. For determina-tion of pharmacological application of kefir, Lee and coworkers(2007) produced artificial asthma problem based on ovalbuminsensitization in a mouse model that produced inflammation inairway system. In such animals when kefir (50 ppm) was ad-ministered through intragastric mode, it displayed anti-allergicand anti-inflammatory effects by inhibiting ovalbumin-inducedeosinophilia in lung tissue. At the same time, hypersecretion ofmucous by goblet cells was also observed in the airway (Eliaset al., 2003). In another attempt, similar result was experiencedby administering kefiran (Kwon et al., 2008). Anti-inflammatoryeffect was also observed when L. plantarum isolated from kefirwas administered orally in mouse model (Lee et al., 2007).

5.5. Hypocholesterolemic Effect

Earlier record of hypocholesterolaemic activity by the con-sumption of fermented dairy products was provided by Mannand Spoerry (1974). Later on, a number of studies con-

firmed these facts in animal and human models (Anderson andGilliland, 1999; St-Onge, 2000; Xiao et al.,2003). Althoughsome scientists reported contradictory results about hypocholes-terolemic activity of fermented dairy products (Nakajima et al.,1992; De Roos et al., 1998), yet the majority of results indi-cated that fermented dairy products, especially kefir, possessedgood hypocholesterolaemic activity (St-Onge 2000; Xiao et al.,2003). People have a great concern about the high cholesterolcontaining foods due to risk of cardiovascular disease. Highercount of lactic acid bacteria in kefir ensures the binding ofcholesterol up to 33% probably due to direct action of microbeson cholesterol through their metabolic products (Hosono andTanako, 1995). It has been noticed that when milk was inoc-ulated with kefir cultures at 24.8◦C and incubated for 24 h, itresulted in an assimilation of cholesterol by 28–65% (Vujicicet al., 1992). Isolated yeast from kefir, deficient in invertase en-zyme, when applied to dairy products (Tamai et al., 1996), wasreported to provide a hypocholesterolemic effect in the product(Noh et al., 1997). Comparing the sheep, cow, and goat milkfor the production of kefir in reference to hypocholesterolemicactivity, it was observed that sheep milk have more beneficial ef-fects as compared to cow and goat milk (Wojtowski et al., 2003).Two substances, i.e, orotic acids and/or hydroxymethylglutaricare thought to restrict rate-limiting enzyme that is important insynthesis of cholesterol (Shahani and Chandan 1979). Anotherresearcher explained a new concept for reduction of cholesterolin humans that is based on loss of orotic acids during kefirfermentation (Ozer and Ozer, 1999). Several scientists reportedthe role of exopolysaccharide for reduction of serum cholesterollevel in rats when they consumed excessive dietary cholesterol(Maeda et al., 2004). In most recent study, Lactobacillus plan-tarum MA2 from Chinese Tibet kefir was found effective forcholesterol lowering activity both in vitro and in vivo (Wanget al., 2009). Soya milk kefir was observed equally effective asmilk kefir for not only total cholesterol lowering characteristicsbut it also lower serum triacylglycerol, and LDL cholesterol(Liu et al., 2006a). These findings demonstrate that kefir orits components have greater potential to be used as hypocholes-terolaemic substance (Shahani and Chandan 1979; Maeda et al.,2004; Liu et al., 2006a).

5.6. β-Galactosidase Activity

Lactose is the main carbohydrate disaccharide present in allmammalian milks and lactose intolerance is the disorder asso-ciated with indigestion of lactose. A large segment of worldpopulation is suffering from this ailment. The use of fermenteddairy products is only practical solution to this problem (Kolarset al., 1984). The most probable reason for this action is the ac-tivity of β-galactosidase enzyme that works in synergism withyogurt starter culture bacteria (Lactobacillus delbrueckii subsp.bulgaricus and Streptococcus salivarius subsp. thermophilus)(Hertzler and Clancy, 2003). β-galactosidase, which is natu-rally present in kefir grains, reduces the lactose content through

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hydrolysis process thus making the product suitable for lactoseintolerant persons (De Vrese et al., 1992). Kefir may be equallyimportant as yogurt for treatments of bad breath in lactose-intolerant adults (Hertzler and Clancy, 2003). Lesser lactosecontents and higher β-galactosidase activity in kefir make itsuitable for lactose-intolerant persons by improving lactose di-gestion and reduce the chance of flatulence (De Vrese et al.,1992; Hertzler and Clancy, 2003).

5.7. Gastrointestinal Proliferation

Kefir is widely believed to have a prodigestive effect in gas-trointestinal tract that constitutes the largest interface betweenanimals and their external environment (Jianzhong et al., 2009).As a barrier, it prevents the penetration of harmful entities suchas food antigens (Umeda et al., 2005). Fermented milk productshelp in re-establishing the beneficial lactic acid microflora insmall intestine by inhibiting undesirable microorganism. Theseantibacterial properties are largely dependent on culture activity,temperature, time of storage, and the initial level of contamina-tion (Marquina et al., 2002). New microbial flora help in proteindigestion and reduce glycemic index (Urdaneta et al., 2007),especially Campylobacter jejuni colonization in the caecum ofchicks and rats may affect intestinal mucosa and systemic im-mune response (Troreux and Schmucker, 2001; Zacconi et al.,2003). This also resulted in mucosal resistance to gastrointesti-nal infection in mice (Liu et al., 2002). Regular intake of kefir isnot only beneficial in the treatment of gastrointestinal disordersbut it has also got applications for quick healing post-operativecases (Fil Chakova and Koroleva, 1997). Data regarding in-take of kefir in infants indicated that infants suffering fromintestinal infection rapid inhibition of Shigella and Salmonellain 7–11 days were observed after consumption of bifido kefir(kefir containing physiological cells of Bifidobacterium bifidum)(Murashova et al., 1997). These results, when compared withingestion of normal kefir (without Bifido factor) recovery con-dition was approached after 12–18 days (Molokeev et al., 1998).A more recent study indicated that harmful effect of B. cereuscould be mitigated by the kefir exoplysaccharide, i.e., kefiran.This polysaccharide also has a capacity to modulate the viru-lence of microorganisms in the context of intestinal infections(Medrano et al., 2008; Medrano et al., 2009).

5.8. Bacterial Colonization

Lactic acid bacteria of kefir colonize in the intestine for smallperiod of time and produce favorable factors (probiotic). Towork as probiotic intestinal adhesion to epithelium or/and tran-sit are vital factors in determining the host’s immune reactivity.Residence time of these microflora in intestine depends on theability to survive against varying concentration of bile salt andability to withstand the extreme conditions that may prevail inthe intestine (Schiffrin et al., 1997). Fortunately, about 85%

Lactobacillus species isolated from kefir have the capacity toresist oxgall and many of them are able to adhere to enterocyte-like cells (Santos et al., 2003). In a recent study, it was foundthat LAB from kefir grains possessed excellent tolerance tosequential simulated gastrointestinal tract conditions, and thatkefiran (kefir exopolysaccharide) had a significant protectiveeffect on LAB in hostile environments. Since the from LABkefir grain possess excellence tolerance, so they are excellentcandidates to be used as health-promoting probiotics in food in-dustry (Jianzhong et al., 2009). Similarly, Kluyveromyces lactisand Kluyveromyces ladderae are able to tolerate high acidity ofintestine and adhere to human intestine by using some proteina-ceous factors (Kumura et al., 2004). One of these proteinaceousfactor was mentioned by Garrote et al. (2004) in Lactobacilluskefir and Lactobacillus parakefir. These factors can be char-acterized as S-layer protein having adhesive properties to joinCaco-2 cells (Cole and Fuller, 1984).

5.9. Anti-Diabetic Effect

Kefir that was produced in conjunction with soymilk andRhodiola extracts exhibited a better anti-diabetic functional-ity (Kwon et al., 2006). This product mobilized the phenolicscompounds, which alter the postprandial hyperglycemia (Kwonet al., 2006). Water and methanol-soluble fractions of kefran-kefrin was observed suitable in management of Type II diabetes(Teruya et al., 2002). Later research also proved the capacity ofkefiran to lower blood glucose in KKAy mice to a significantlevel (Maeda et al., 2004).

5.10. Antiallergic Properties

Food allergy is the major problem in every part of the globeand, like other atopic disorders, its incidence appears to be in-creasing. Regular consumption of kefir milk and soy-based kefirproducts restrain the IgE and IgG1 responses. Thus by alter-ation in gut microflora we can achieve the goal for prevention offood allergy and enhancement of mucosal resistance to gastroin-testinal pathogen infection can be achieved (Liu et al., 2006b).Another study revealed that kefir inhibits ovalbumin-inducedeosinophilia in lung tissue and mucus hypersecretion. By do-ing so, kefir exhibits great therapeutic potential for treatment ofallergic bronchial asthma (Lee et al., 2007).

5.11. Antioxidative Properties

Dietary components play a major role in protecting the bodyagainst oxidative damage. Kefir contains a series of componentsthat have good antioxidant activity (Chen et al.,2006). Guvenet al. (2003) compared the antixoidative consequence of ke-fir and vitamin E against oxidative damage of CCl4 in animalmodel. Results indicated that both vitamin E and kefir have a

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capacity to protect tissues against CCl4-induced damage, andkefir offered more protection as compared to vitamin E (Guvenet al., 2003).

5.12. Effect on Blood Pressure Level

Kefiran in animal models significantly reduce blood pressureand serum cholesterol especially in the test organism consuminghigher amounts of dietary cholesterol (Maeda et al., 2004). Thereduction in blood pressure may be attributed to suppressing theangiotensin-converting enzyme (ACE). ACE activity influencesblood pressure through different means. ACE converts AT I toAT II. AT II is a potent vasoconstrictor and it also stimulatealdosterone in kidney to retain more liquid in the body, thusincreases blood pressure (Figure 3). Two out of sixteen peptidesfrom kefir showed ACE-inhibitory activity (Quiros et al., 2005).Positive results were also noticed when powdered milk fermen-tation was carried out using Lactobacillus helveticus isolatedfrom kefir(Aihara et al., 2005).

5.13. Protection Against Apoptosis

Exposure to UV irradiation cause production of ROS in skincells and damage melanocytes along with other skin cells. Sev-eral other problems that may originate are freckles, liver spots,skin cancer, and wrinkles. These radiations may also causethe apoptosis of stem cells in intestine (Nagira et al., 1999a).Kefran-kefir has the capacity to scavenge the superoxide radi-

Figure 3 Role of kefir in regulating blood pressure. (Figure available in coloronline).

cals and this providing protection against UV damage of humanmelanoma HMV-1 cells (Nagira et al., 1999b). In another study,researchers investigated the role of kefir extract on apoptosis ofHMV-1 cells caused by UV irradiation. Promising results indi-cate that DNA kefir extract is capable of repairing DNA damagecaused by UV irradiation and can suppress apoptosis (Nagiraet al., 1999b). X-ray-induced apoptosis in the colon of rats wasalso minimized by using kefir milk (Matsuu et al., 2003). In ratsmodel kefir provide antiapoptic protection for colonic epithelialstem cells by cessation of caspase-3 activation. In patients withmalignancy that are undergoing irradiation therapy, kefir treat-ment may lower the adverse side effects of irradiation in suchpatients (Nagira et al., 1999b; Matsuu et al., 2003).

6. CONCLUSION

There is a growing trend to consume nutritional food prod-ucts having some health benefits among various segments of thepopulation on each and every part of this globe. This desire di-rected the consumption of kefir and other cultured milk in dailydiet. Due to high nutraceutical and therapeutic potential, kefirand related products are ranked at top position. The beneficialhealth characteristics in kefir are attributed to protein, vitamins,antioxidants, minerals, and certain biogenic compounds. Thehealth benefits associated with kefir are gastrointestinal prolif-eration, antibacterial spectrum, anticarcinogenic effect, hypoc-holesterolemic effect, antidiabetic properties, antimutagenic ac-tivity, β-galactosidase activity, scavenging activity, lactic acidcontent, effect on lipid and blood pressure level, protectionagainst apoptosis, antiallergic properties, anti-inflammatory ac-tion, bacterial colonization, and immune system booster. Kefiris able to normalize intestinal microflora and is highly suitablefor consumption by normal and sick adults as well as infants.

ACKNOWLEDGMENTS

This work was supported by a grant from Science and Tech-nology Supporting Project of China National Eleventh Five-Year-Plan (No. 2006BAD 04A 06).

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