Acta Universitatis Latviensis, 2006, Vol. 710, Biology, pp. 117–129
Probiotics as functional food: microbiological and
medical aspects
Malda Maija Toma1*, Juris Pokrotnieks2
1Institute of Microbiology and Biotechnology, University of Latvia, Kronvalda Bulv. 4, R?ga
LV-1586, Latvia
2R?ga Stradi?š University, Dzirciema 16, R?ga LV-1007, Latvia
*Corresponding author, E-mail: toma@lanet.lv
Abstract
Probiotic bacteria are sold mainly in fermented foods, and dairy products play a predominant role
as carriers of probiotics. Functional dairy foods are well suited to promoting the positive health
image of probiotics for several reasons: (i) fermented foods and dairy products in particular, already
have a positive health image by their traditional use for centuries; (ii) people are familiar with the
fact that fermented food contain living microorganisms; (iii) probiotics are used as starter to join
together the positive images of fermentation and probiotic cultures. Probiotics are de? ned as live
bacterial preparations (food or medicine) with clinically documented health e? ects in humans.
Most probiotics exert bene? cial e? ects by modulating the mucosal barrier function and immune
activity. Probiotics have speci? c properties and targets in the human intestinal tract and intestinal
microbiota. Understanding the mechanisms by which probiotics in? uence the normal intestinal
micro? ora and counteract aberrancies in micro? ora can facilitate the use of probiotics for dietary
management and reduction in risk of speci? c diseases. In reference of the immune system, many
studies have pointed out that not only pro- and prebiotics, but also single micronutrients incorporated
into functional foods contribute to an enhancement of immunocompetence. In this article, the e? ect
of some functional foods and ingredients such as probiotics and selenium on health and especially
immune function are reviewed.
Key words: functional dairy products, functional foods, probiotics, selenium.
Introduction
Th e term “functional food” was ? rst introduced in Japan in the mid-1980s and refers to
processed foods containing ingredients that aid speci? c bodily functions in addition to
being nutritious (Swinbanks, O’Brien 1993). Generally, they are considered as those foods
intended to be constituted as part of a normal diet, and that contain biologically active
components, which o? er the potential of enhanced health or reduced risk of disease.
Research has demonstrated that nutrition plays a crucial role in the prevention of
chronic diseases, as most of them can be related to diet. Functional food enters the concept
of considering food not only necessary for living but also as a source of mental and
physical well-being, contributing to the prevention and reducing of risk factors for several
diseases or enhancing certain physiological functions. Dairy products form the major part
of functional products. To understand their success it is important to realise that milk
is a natural and highly nutritive part of a balanced daily diet. Developing functionality

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in dairy-based products simply means modifying and/or enriching the healthy natural
characteristics of the original base. Milk and some other dairy products were recognised
as important foods as early as 4000 B.C. Th e Roman historian Plinio recommended the
use of fermented milk for treating gastrointestinal infections. Th e French paediatrician
Tissier proposed in the early 1900s that bi? dobacteria could be e? ective in preventing
infections in infants, as they were the predominant component of the intestinal micro? ora
in breast-fed infants. Th en Metchniko? suggested that consumption of fermented milk
could reverse the putrefactive e? ects of the gut micro? ora. Th is concept has developed
particularly over the past two decades through trend scienti? c evidence based on placebo-
controlled clinical trials showing that particular strains have associated health bene? ts.
Nowadays dairy products are excellent media to generate an array of products
that ? t to current consumer demand for functional food. Fermented dairy products
enriched with probiotic bacteria have developed into one of the most successful parts
of functional foods. Th e food industry is especially active in studying probiotics because
the gastrointestinal tract is one of the richest zones of biodiversity within the body with
at least 450 known species of microorganisms commonly found there. Some of the most
Fig. 1. Some representatives of human gut micro? ora: Lactobacil us GR-1 (dark blue); Lactobacil us
RC-14 (light blue); Escherichia coli (red); Bacteroides fragilis (orange); Streptococci (green);
Staphylococci (cyan); Campylobacter jejuni (blue green); Klebsiel a (purple). Reproduced with
permission from Th e S
Th
Th ci
c e
i n
e t
n itsts Vol. 16 (2002).

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Probiotics as functional food
119
Table 1. Microorganisms considered as probiotics (Holzapfel et al. 2001).
Lactobacillus
Bi? dobacterium Other lactic acid
Non-lactic acid


bacteria
bacteria
L. acidophilus
B. adolescentis
Enterococcus faecalis
Bacil us cereus var. toyoi
L. amylovorus
B. animalis
Enterococcus faecium
Escherichia coli Nissle 1917
L. casei
B. bi? dum
Lactococcus lactis
Propionibacterium freudenreichii
L. crispatus
B. breve
Leuconostoc mesenteroides Saccharomyces cerevisiae
L. delbrueckii
B. infantis
Pediococcus acidolactici
Saccharomyces boulardii
subsp. bulgaricus

L. gal inarum
B. lactis
Streptococcus thermophilus
L. gasseri
B. longum
Sporolactobacil us inulinus
L. johnsonii
L. paracasei
L. plantarum
L. reuteri
L. rhamnosus
important representatives are shown in Fig. 1. Functional dairy products have been the
focus of intensive research and product developments over the last two decades regarding
putrefactive intestinal bacteria; there has been much interest in the possible health bene? ts
of probiotic microorganisms. Dairy products, accounting for 65 % of the total European
functional foods market, are at the forefront of probiotic developments (Hilliam 2003).
Probiotics and prebiotics: de? nition and mechanism of action
Vergin ? rst introduced the term “probiotics”, when he compared in his paper “Anti- and
Probiotika”, the detrimental e? ects of antibiotics and other antimicrobial substances on
the gut microbial population with factors “probiotika” favourable to the gut micro? ora
(Vergin 1954). Th en probiotics were de? ned as non-pathogenic microorganisms when
ingested, exert a positive in? uence on host health or physiology (Fuller 1989). Now, the
de? nition of Food and Agriculture Organisation of the United Nations/World Health
Organisation (FAO/WHO 2001) for probiotics is “Live microorganisms, which when
administered in adequate amounts, confer a health bene? t on the host”. Th is de? nition
retains the historical elements of the use of living organisms for health purposes but does
not restrict the application of the term only to oral probiotics with intestinal outcomes
(Reid 2006). Th is is important considering that vaginal applications of probiotics have
existed for more than 20 years (Reid, Bruce 2006).
Microorganisms that are probiotics (Table 1) in humans include yeast (Periti, Tonelli
2001), bacilli (Pinchuk et al. 2001), Escherichia coli (Midtvedt 1997), enterococci (Lund,
Edlund 2001), and the more commonly used bi? dobacteria and lactic acid bacteria, such
as lactobacilli, lactococci and streptococci (Salminen et al. 1998; Isolauri et al. 2002). Th e
International Dairy Federation has recently published a bulletin summarising the evidence
for the e? ect of probiotic cultures on a range of diseases and disorders in humans. Th e

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bulletin No 380/2003 contains a section (Ouwehand et al. 2003) reviewing the evidence
for clinical e? ects in an extensive range of conditions including lactose maldigestion,
diarrhoea, immune modulation, in? ammatory bowel syndrome, constipation, necrotising
enterocolitis, Helicobacter pylori infection, small bacteria overgrowth, colorectal cancer,
breast cancer, allergy, serum cholesterol and blood pressure decreasing, coronary heart
disease, urinary tract infection, upper respiratory tract and related infections. Th ereby
probiotics have multiple mechanisms of action (Table 2), including prevention of
pathogenic bacterial growth, binding to or penetration of pathogens to mucosal surfaces,
stimulation of mucosal barrier function, production of antimicrobial agents or altering
immunoregulation, decreasing proin? ammatory and promoting protective molecules
(Sartor 2005; Novak, Katz 2006). It was demonstrated (Meier, Steuerwald 2005) that not
only viable or dormant bacteria administered to the intestinal tract but also probiotic
DNA is active, even if injected subcutaneously. Attention is now focusing on the intestinal
survival of probiotic bacteria, their competition with the abundant resident microbiota,
identi? cation of activity and clari? cation of mechanisms of action. Probiotics have to
survive gastrointestinal transit and arrive viable to contribute positively to the activity
of the intestinal micro? ora, and thus, the health of the host (Table 3). A recent paper
hypothesised that probiotics might even help detoxi? cation in cases of mercury poisoning
(Brudnak 2002).
Another interesting aspects concerns the antigenotoxic activities of probiotics. Our
experiments have suggested that the potential genotoxic e? ect of furazolidone, nalidixic
acid and 4-nitroquinolone-N-oxide could be strongly reduced by in vitro co-incubation
with probiotic bacteria, belonging to three genera and probiotic yeast (Raipulis et al.
2005; Toma et al. 2005). Surprisingly, the nonprobiotic yeast Saccharomyces carlsbergensis
also possesses antigenotoxic activity but to a minor extent (Toma et al. 2005). Th e
antigenotoxic properties were shown only by live cells but heat treated cells did not act
as an antigenotoxin. Th ese results are of considerable interest with the increasing demand
Table 2. Some examples of target speci? c search for optimal probiotics (Salminen et al. 2005)
Target for probiotic action
Selection criteria
Alleviation of lactose maldigestion
High lactase producing strongly site speci? c
probiotics
symptoms
Intestinal in? ammation
Site speci? c adhesion properties, anti-

in? ammatory cytokine expression, mucosal

properties to alleviate permeability disorder and

gut micro? ora abberancy
Alleviation or food allergy symptoms,
Adherence to small intestine, induction of local
reducing the risk proteolytic properties of
transforming growth factor-? production
atopic disease
Reducing the risk of colon cancer
Target speci? c adhesion to distal or proximal

colon, mucosal butyric acid production,

competitive exclusion of in? ammatory

bacteria, toxin binding and promotion of

nontoxigenic mucosal micro? ora

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121
Table 3. Th e probiotic e? ects reported and their putative mechanisms (Sanders 2003)
Bene? t Function
Proposed mechanism
Digestive Irritable bowel syndrome, symptoms
Change in populations or activities of the
comfort a? ecting the gastrointestinal tract in
intestinal micro? ora

general (constipation, non-pathogenic

diarrhea, distension, ? atulence, cramp,

halitosis of a digestive cause)

Lactose intolerance
Delivery of microbial lactase to the small


intestine
Defense Allergy (atopical eczema, allergy to the
Translocation, barrier e? ect

milk, rheumatoid arthritis)

Cariogenicity
Changes in the populations, activity of the


oral micro? ora or its ability to adhere to


the teeth

Carcinogenicity, mutagenicity, tumor
Absorption of the mutagen, stimulation


of the immune system, inhibition of


carcinogen production by the intestinal


micro? ora

Diarrhea linked to antibiotics, diarrhea Competetive exclusion, translocation/

caused by Rotavirus, colitis caused by
barrier e? ect, immune response promoted
C. di? cile, nosocomial diarrhea
Helicobacter pylori
Antipathogenic activity

Immunomodulation (immune status,
Interaction with the immune cells or cell

vaccinal response)
receptors leading to an increase in the


phagocytic acivity of the white cells,


increasing IgA levels aft er exposure to the


antigen, increasing the proliferation of the


intra-epithelial leukocytes, regulating the


Th 1/Th 2 ratio, induction of cytokine


synthesis

Intestinal in? ammation, ulcerative
Immune response downregulated

colitis, Crohn’s disease, pouchitis

Excessive intestine bacterial growth
Antimicrobial activity, competitive


exclusion

Vaginosis, urinary infections
Antipathogenic activity, competitive


exclusion
Others
Lowering of blood cholesterol
Deconjugation of the bile acids

Endotoxemia combined with cirrhosis
Inhibition of the production of endotoxins


by the intestinal micro? ora

Hypertension
Cellular constituents or peptides derived


from fermentation acting as inhibitors of


ACE (angiotensin-converting enzyme)

Renal calculi
Changes in the digestive ? ora in? uencing


the breakdown of oxalate

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for functional foods, especially functional dairy products, such as yogurts and fermented
milks, containing Lactobacil us and Bi? dobacterium.
Prebiotics are de? ned as nondigestible substances (dietary ? ber) that exert some
biological e? ect on humans by selective stimulation of growth or activity of bene? cial
microorganisms either present on therapeutically introduced to the intestine. Prebiotics
undergo fermentation by probiotics in the large intestine. Prebiotics are sources of energy
for probiotics. Clinical trials have shown that several di? erent oligosaccharides can be used
to stimulate bi? dobacteria in the gastrointestinal tract and protect against gastrointestinal
infections (Novak, Katz 2006).
Prebiotics are inulin, fructo-oligosaccharide, galactooligosaccharide and lactulose.
With regard to a possible role for prebiotics in reducing the risk of diseases, the evidence is
limited. Th e area where evidence can be considered promising is constipation (Roberfroid
2000) and gastrointestinal infections (Novak, Katz 2006). Although prebiotics improve
calcium absorption (Abrams et al. 2005), their positive role in reducing the risk of
osteoporosis needs to be supported by more human studies. Th e reduction of the risk of
obesity and possibly of type 2 diabetes, both of which are known to be associated with
insulin, also needs further investigation.
It has been observed that modi? cation of intestinal micro? ora by inherently selectively
fermented prebiotics is central in determining their nutritional properties (Van Loo 2004).
Prebiotics interact positively through the large intestinal surface with various physiologic
processes and are thought to improve health status by reducing risk for disease.
Probiotics, intestinal micro? ora and health
One of the main selection criteria for probiotics has been competitive exclusion of
pathogens. Probiotics compete directly or delay the adhesion of pathogens on stereo-
speci? c receptors on the mucosal surface of gastrointestinal tract. Th ey also have an
in? uence on the development of intestinal micro? ora in infants. Th e outcome of the
microbiota development and competitive exclusion depends on the speci? city of the
microorganisms and their adhesion for the receptors and the relative concentrations of
competing bacteria. Th e e? ective dosage of probiotics is thus determined by the relative
a? nity for receptor sites (Salminen et al. 2005). Di? erent probiotics and even di? erent
strains have distinct modes of action and the clinical e? cacy of various probiotics has
been proven in distinct indications (Holst, Breves 2005).
Gut health and immunity
Th e gut and immune system form a complex integrated structure that has evolved to
provide e? ective digestion and defence against ingested toxins and pathogenic bacteria.
Around 60 % of functional foods, principally pro- and prebiotics, are targets of the gut
and the immune system. A characteristic feature of gastrointestinal immune systems
is its ability to exhibit tolerance towards innocuous dietary antigens and commensally
micro? ora acquired during infancy and to mount a vigorous immune response to
potentially pathogenic microorganisms. Th e execution of these disparate functions
requires that the immune system surveys all the lamina antigens, to sort “harmful” from
“harmless” antigens and to tightly regulate the ensign e? ect or responses; a failure to

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regulate the mucosal immune response results in a range of clinical disorders such as
allergy, in? ammation and autoimmune diseases (Gill 2003). To perform these functions
the gastrointestinal tract harbours the largest immune system in the whole body, over 70
% of the total immune system being located in this area. Th e gastrointestinal immune
system consists of two main components: organized lymphoid follicles (Payer’s patches
and mesenteric lymph nodes, and a large number of immunocompetitive cells – the
organised tissues) serve as a potential site for the induction of immune responses to new
antigens, whereas the intestinal mucus serves as the e? ector site.
Probiotics and the immune system
Th e e? ect of probiotics on the immune system has been the subject of numerous studies
over the past 20 years. Th ere is evidence that certain strains of probiotics are able to
stimulate as well as regulate several aspects of the natural and acquired immune response.
It has also been demonstrated that there are signi? cant di? erences between the ability
of Bi? dobacterium and Lactobacil us strains to in? uence the functioning of the immune
system.
Th e initiation, maintenance and resolution of both innate and acquired immune
responses are regulated by cell-to-cell communication via cytokines. Th e intake of
probiotics in humans has been shown to enhance cytokine production in vivo, and by
peripheral blood mononuclear cells ex vivo (de Simone et al. 1989). Probiotic intake has
been reported to be e? ective in restoring the age-related decline in phagocyte function
(Gill 2003). Strain- and dose-dependent di? erences in the ability of probiotics to
in? uence immune function are well documented (Gill 1998). Th e intake of speci? c strains
of probiotics has also been shown to enhance humoral immune responses to natural
infections and systematic or oral immunization in human subjects (Majamaa et al. 1995;
Fukushima et al., 1998). It is important to note that probiotic administration is also known
to stimulate antibody responses to completely unrelated antigens as well as to themselves
(Yasui et al. 1989).
Probiotics are thus suggested to confer protection against enteropathogens by:
• stimulating cytokine production;
• enhancing the phagocytic capacity of polymorphonuclear cells and macrophages;
• augmenting NKH cell activity;
• enhancing speci? c antibody responses to pathogens.
Minimum concentration of probiotic required for bene? cial e? ect
Th e information to recommend the minimum concentrations of probiotic bacteria for
e? ective function is still insu? cient. Nevertheless, adequate numbers of viable cells,
namely the “therapeutic minimum” need to be consumed regularly for transfer of the
“probiotic” e? ect to consumers (Viljoen 2001). Consumption should be more than 100
g per day of bio-yogurt containing more than 106 CFU ml-1. Shah (2000) amongst others
has suggested a minimum viable number of 106 CFU ml-1 or gram but recommends 108
CFU g-1 to compensate for reduction through passage through the gut. Yogurt is a classic
example of a functional food with probiotics. Yogurt with probiotics, called bio-yogurt,
should contain living bacterial cells. According to regulation yogurt should contain 2 ×

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106 living bacteria in 1 ml at the end of the recommended storage period. Th e daily dose
of probiotic microorganisms should reach 1 × 109 cells. Th e titre of bacteria in fermented
drinks reaches 108 to 109 ml-1 and decreases with storage. It is also possible to use tablets or
capsules as additives to foodstu? s, that contain lyophilised cultures of bacteria. Probiotics
are available as pharmacopoeia preparations such as Linex 1.2 × 107, Muta? or 2.5 × 109,
Lactoseven 1 × 109. Jogurt capsules 2 × 109 contain freeze-dried bacterial cells per caps,
correspondingly. Th e question is – which is more e? ective way to take viable or lyophilised
bacteria – in yogurt or capsules? Th e intake of functional dairy products also is more
physiologically and more acceptable for patients or consumers as well. Within the last
decade, consumers have made increasing reference to functional food, recognising the
relationship between nutrition and health to the point of endowing an overreliance
on pharmaceuticals and regarding prescription drugs as oft en being unnecessary, too
expensive, unsafe and of dubious bene? t once all the risks are considered (Bagchi 2006).
Safety of probiotics
Th e safety of probiotics can be described in short:
(i) centuries of use fermented products;
(ii) no reports of probiotic pathogens;
(iii) safe use of active cultures in thousands of subjects have demonstrated that
probiotic intake is safe.
Th is past safe history is very important regarding use by pregnant woman and newborn,
because there is some limitation for clinical trials. At the same time, some scientists have
doubt about reasonability in taking a high dose of viable bacteria (Henriksson et al. 2005). A
review outlining the safety of current probiotic compounds has been published (Borriello
et al. 2003). Cases of infection caused by Lactobacil us and Bi? dobacteria are extremely
rare. Previous research into the protective mechanisms associated with probiotic bacteria
focused on the bacteriology of the gut and concentrated on intestinal colonisation and
probiotic-induced suppression of pathogen growth and/or invasion (Clancy 2003).
Indeed, the concept of a balance existing in the intestine, involving competition between
probiotic and pathogenic bacteria for speci? c binding sites on intestinal epithelial cells,
has been well established in the literature. However, recent research has turned toward
understanding the role of probiotics and their products, and in enhancing and modulating
innate and adaptive immune responses in the organism by other mechanisms (Fedorak,
Madsen 2004). Th e ability of immune and epithelial cells to discriminate between di? erent
microbial species through activation of Toll-like receptors (Kadowaki et al. 2001; Vinderola
et al. 2005) indicates that probiotics may show some of their protective functions through
modulation of immune activity and epithelial function in gut.
Probiotics and selenium
Selenium (Se) has been recognized as an essential nutrient in the late 1950s, when it was
found that it could replace vitamin E in the diets of animals (Schwartz et al. 1957). It is hard
to overestimate the importance of Se to biological systems. Its crucial role is underlined
by the fact that it is the only trace element to be speci? ed in the genetic code (Rayman
2002). It is speci? ed as selenocysteine, now recognized as the 21st aminoacid, as it has its

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125
own codon and speci? c biosynthetic and insertion mechanism (Gladyshev 2001). About
40 mammalian selenoproteins have been identi? ed as having enzymatic redox activity,
structural and transport functions. Th ereby it is suggested that Se adequacy is crucial
to human and animal health. A detailed review of Se de? ciency symptoms, pathology
and biochemical mechanisms was published by Gibson (2005). Low or diminishing Se
status in some parts of the world, notably in Scandinavian and some other European
countries, such as the UK, Baltic States, Croatia, Poland, Hungary, in? uences human and
animal health. Th ere is evidence that Se de? ciency may contribute to development of a
form of heart disease, hypothyroidism, and a weakened immune system (Combs, 2000;
Zimmerman, Kohrle 2002). Th ere is also evidence that Se de? ciency does not usually
cause illness by itself, because no one speci? c disease has been found, but it can make the
body more susceptible to illnesses caused by other nutritional, biochemical or infectious
stresses (Beck et al. 2003).
Epidemiological evidence in humans suggests a role for selenium in reducing cancer
incidence and mortality, especially from prostate and colorectal cancer (Mantovani
et al. 2004; Luty-Frackiewicz 2005; Finley 2006). Th e latest investigations show that Se
administration decreases the toxicity of inorganic and organic forms of mercury (Cabanero
et al. 2006). Th ere are three arguments for increasing the Se intake: (i) Se de? ciency may
leave, than optimally protected against a number of adverse health conditions; (ii) Se
intakes above those required to replete glutathion peroxidases and other selenoenzymes
appear to confer additional health bene? ts and (iii) Se intake is low or marginal in many
countries. Se enters the food chain through plants, but its incorporation is dependent
not only on soil content, but also on the soil pH, rainfall, land pro? le, and activity of
microorganisms (Combs 2001). Increasing Se intake from normal food sources is di? cult
to achieve. Meat and dairy products, eggs, Brazil nuts and wheat products are natural Se
sources, but it is di? cult to achieve the EU recommended 55 µg day-1 dose. Th erefore it
is necessary to perform food enrichment with dietary supplements of Se. Today situation
is even more complicated because since August 1, 2005 dietary supplements containing
organic Se forms are prohibited in the EU.
Our new project deals with the development of a novel type of functional food
– Se enriched yogurt using probiotics able to concentrate Se intracellulary. It has been
demonstrated that Lactobacil us accumulates some inorganic Se compounds in the form
of selenocysteine (Calomme et al. 1995). Our experiments showed that supplementation of
MRS broth (Si? n, Germany) with Bioenergostims Ultra Top (? ve inorganic Se compounds)
promote yogurt starter cultures (Lactobacil us bulgaricus + Streptococcus thermophilus)
growth at the Se concentration 100 mg l-1 till 15 % (Toma et al. 2006). Also, yogurt
starter cultures become treatable to low pH in comparison with the control (Table 4).
Supplementation with Se may stabilise membranes against the rigidity due to aging (Garcia
et al. 2005). Preliminary experiments with ? uorescent probe ABM (Kalnina et al. 2000)
suggested an idea that the membranes of bacterial cells are selectively strengthened.
Th e combination of probiotics with Se in one product could confer bene? ts beyond
those of either on its own.
Results with probiotic bacteria Enterococcus faecium demonstrate that the micronutrient
selenium enhances the antimutagenic activity of probiotic bacteria (Križkova et al. 2002).
It shows a potential bene? t for the future development of new Se-enriched probiotic
exhibiting higher antimutagenic properties.

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Table 4. E? ect of selenium on viability (log CFU ml-1) of yogurt starter cultures aft er exposure to 0.2
M HCl-KCl bu? er pH 2.5 (Toma et al. 2006)


Time of exposure (h)

0
1
2
Control
9.9
6.1
3.5
Selenium (100 µg ml-1)
10.3
7.6
5.8
Probiotics and prebiotics as functional food
Probiotics and prebiotics simultaneously present in a product are called synbiotics. Such
a combination aids survival of the administered probiotics and facilitates its inoculation
into the colon. Additionally, the prebiotics induce growth and increase activity of
positive endogenic intestinal micro? ora (Tomasik, Tomasik 2003). It was experimentally
demonstrated that synbiotics protect the organism from carcinogens signi? cantly better
than do either probiotics or prebiotics separately (Gallaher, Khil 1999). Several foodstu? s
with probiotics and prebiotics are available in the Latvian marketplace. One of the best is
synbiotic yogurt Oat Bio Lacto (Bekers et al. 1999).
Summary
Probiotics can be considered functional foods because they provide health bene? ts beyond
the traditional nutrition function. With few exceptions, most probiotic products currently
available contain lactic acid bacteria, which mainly belong to the genera Lactobacil us and
Bi? dobacterium. Th e scienti? c papers published in major microbiological and nutrition
journals suggest evidence of the following bene? cial e? ects of probiotics: normalisation
of the intestinal micro? ora, which both preserves and promotes wellbeing and the absence
of disease (not only in the gastrointestinal tract), the ability to block the invasion of
potential pathogens in the gut, prophylactic or therapeutic treatment for several types of
diarrhoea (independently from aetiology), relief of symptoms of irritable bowel syndrome
and in? ammatory bowel disease, amelioration of lactose intolerance, prevention of colon
cancer, inhibition of Helicobacter pylori, reduction of blood cholesterol level, hypertonia.
Correction of the properties of unbalanced indigenous microbiota forms the rationale of
probiotic therapy. However, an important part of the bene? cial e? ects of probiotics are
related to their immunomodulatory e? ects: immune chancing as well as anti-in? ammatory
activity. Bearing in mind the need for further evaluations, dietary modi? cation towards
a balanced dietary intake of nutrients and probiotics may o? er a tool for both the
management and risk reduction of allergic and autoimmune diseases.
Acknowledgements
Th is work was supported by the Market Oriented Research project 05-37 and the grant 05.1558
of the Latvian Council of Science. Authors are grateful to Dr. G. Reid (Canadian Research and
Development Centre for Probiotics) for his kind permission to use his electronmicrofotographs
and to B. Pitrans, President of Biomedical European Academy Ltd., for stimulating discussions and
support.

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