Probiotik dan Prebiotik

CONTENTS

I. Probiotics...........................................................................................................................335

A. Criteria for Probiotics ................................................................................................335

B. Probiotic Products on the Market .............................................................................337

II. Prebiotics ............................................................................................................................338

III. Microbiology of the Gastrointestinal Tract .......................................................................339

IV. Probiotic Products ..............................................................................................................341

A. Yogurt.........................................................................................................................341

1. Lactase Deficiency...............................................................................................341

2. Cholesterol Metabolism.......................................................................................342

3. Immune Function.................................................................................................343

4. Diarrhea................................................................................................................343

5. Cancer ..................................................................................................................344

6. A Vehicle for Other Nutrients .............................................................................344

B. Kefir ...........................................................................................................................344

1. Fabrication ...........................................................................................................345

2. Health Benefits ....................................................................................................346

V. Fermented Vegetables and Other Foods ............................................................................346

VI. The Future for Probiotics and Prebiotics ..........................................................................347

References .....................................................................................................................................34

7

I. PROBIOTIK

Di dalam pengertian fungsional food, terdapat jenis makanan yang baik bagi kesehatan yang

diproduksi oleh mikroorganisme. Makanan ini disebut probiotik. Setelah metabolism bakteri

diartikan dengan lebih baik, beberapa penelitian membuktikan bahwa mikroorganisme berperan

pada kesehatan manusia dan resistensi penyakit, dan beberapa mikroorganisme diidentifikasi

termasuk dalam produk probiotik, perlu memperluas definisi probiotik menjadi obvious.

became obvious.

Criteria untuk probiotik

Criteria pertama The first

three criteria address practical aspects of selection of appropriate microorganisms for inclusion in

probiotic foods, and the latter two may be more important from a consumer-acceptance and

regulatory

point of view. Probiotik yang ideal akan memenuhi semua criteria tapi, daftar bakteri yang

memenuhi sebagian criteria dan yang mempunyai bukti ilmiah tentang efficacy dan telah

incorporated ke dalam makanan, tidak lama.agar menjadi efektif, bakteri probiotik harus tiba

pada bagian/tempat beraksi dalam jumlah yang cukup banyak untuk menimbulkan efek

. hal ini dapat dilakukan dengan mudah dengan menggunakan bakteri yang resisten atau dengan

menyediakan bakteri hidup dalam jumlah yang besar pada saat konsumsi untuk mengatasi

kehilangan selama melewati saluran gastrointestinal. Beberapa pabrik juga menggunakan kapsul

salut enteric yang tidak hancur pada ph di dalam lambung untuk melindungi bakteri.

Criteria dari mikroorganisme yang termasuk dalam makanan dan minuman probiotik

1. mikroorganise asli manusia Microorganism of human origin

2. tahan terhadap kondisi saluran cerna, bile, dan enzim found in the human GI tract

3. kemampuan untuk colonize usus Ability to colonize human intestine

4. aman dikonsumsi manusia

5. Scientifically proven efficacy

Ini ngejelasin tentang bakteri yang masuk GIT

The setting of a minimum number of viable

microorganisms in a food to ensure probiotic effects is an important decision. The Fermented

Milks and Lactic Acid Bacteria Beverages Association in Japan has set a minimum of 107

bifidobacteria/g or ml. Only bacteria that can survive passage through the stomach and can

colonize the intestines will exert any effect on the host. This was most clearly shown by Pedrosa

and colleagues. In healthy elderly persons fed yogurt containing Lactobacillus bulgaricus and

Streptococcus thermophilus, these two organisms could not be found in intestinal contents after

feeding, and there were no changes in three bacterial enzyme activities. When healthy subjects

were fed live Lb. gasseri (Lb.acidophilus strain MS 02), a human strain capable of adhering to

intestinal cells, the organism was found in all subjects and the activities of β-glucuronidase,

nitroreductase, and azoreductase were all significantly reduced. This study emphasizes the need

to measure both the fate of the ingested bacteria and metabolic effects to ensure proper

interpretation of results. The whole premise of a functional food is that certain commonly

eaten foods contain active ingredients that can fight or prevent disease and infection. With

advances in analytical techniques, the identification of new active ingredients occurs every day.

For probiotics, however, the identity of the active ingredient may not be as straightforward

because there is always more than one possibility. The active agent could be one or more of the

live microorganisms in the food, or it could be a metabolite produced by one of the

microorganisms themselves, or it could be a fermentation product that has been formed due to

the action of the microorganism(s) on the original product. Indeed, depending on the probiotic in

question, each of the above arguments has been used to explain the beneficial effects of the

probiotic.

TABLE 17.3

Possible Probiotic Microorganisms

Lactobacillus Bacteria

II. PREBIOTIK

The concept of a prebiotic arose from two observations: (1) bacteria, like any other living

organism, have (sometimes specific) nutrient requirements and (2) some nutrients, particularly

complex carbohydrates, pass undigested into the colon where they are utilized by resident

bacteria.

1995, Gibson and Roberfroid defined a prebiotic as “nondigestible food ingredient that

beneficially affects the host by selectively stimulating the growth or activity of a limited number

of bacteria in the colon.” Rather than supplying an exogenous source of beneficial bacteria, the

concept of a prebiotic proposes to increase the number of certain target bacteria already in the

colon. Attention has centered mainly on the increase of Lactobacillus and Bifidobacterium as the

two main groups of “friendly bacteria” to increase. Variation in individual response is often high

and, as cautioned

by Roberfroid, the prebiotic effect may depend on the initial level of target bacteria.

The goal of increasing selected bacteria by feeding prebiotics has often been the production

of various short-chain fatty acids (SCFAs) because of their impact on the lower gut environment,

metabolism, and disease prevention.

The SCFAs are quickly absorbed and can serve as an energy source for the host, especially

between meals. They contribute to fecal pH and thereby influence colonic function and perhaps

the risk of cancer.

The effects of feeding a prebiotic such although gut-transit time can be shortened by feeding

particular bacterial strains. The combination of live bacteria in a food and the inclusion of

nutrients (usually sugars) that can be used by those bacteria as the two traverse the GI tract has

resulted in what have been termed symbiotic foods. The most popular combination to date

appears to be Bifidobacterium and fructooligosaccharides, but other combinations are possible, if

not practical.

III. MICROBIOLOGY OF THE GASTROINTESTINAL TRACT

TABLE 17.5

Bacterial Genera Found in Human Intestinal and

Fecal Samples

The human microbiota is complex, difficult to study, and is influenced by many factors. Study of

the microorganisms that populate human GI tracts is hampered by the fact that sampling

opportunities are limited, variation between individuals is great, there is no totally relevant

animal model, such research is time-consuming and expensive, and advances in this area of

research are obviously dependent on advances in microbiology. The recent use of molecular

biology techniques has allowed the study of the human GI tract microbiota using non-media

dependent methods. Fluorescent in situ hybridization (FISH), and polymer chain reaction (PCR)

together with denaturing gradient gel electrophoresis (DGGE) are now being used for definitive

and comparative bacterial population studies. Even the simplest questions, such as how many

and what kind of bacteria are important in the human GI tract, are not easy to answer or to find a

consensus in the literature. Indeed, at least one author has stated that due to difficulties in

obtaining proper samples, the crudeness of the methods used to count the various types of

bacteria, and the short duration of most diet intervention studies,

very little is really known about the human microbiota and factors that affect it.

To date, most of our understanding of the human microflora comes from analyses of fecal

contents, which may severely limit our understanding of events further up the GI tract.

There is agreement about the changes, in general terms, in the bacterial population that occur

during the passage from newborn to infant to adult. Vaginally delivered babies have nearly

sterile GI tracts, which soon become colonized, either with large numbers of Bifidobacterium

and Lactobacillus in the case of breast-fed babies or Bacteroides sp and Eschericha coli

in the case of bottlefed babies. Bifidobacterium are considered as desirable, and so attempts have

been made to add prebiotics to infant formula to encourage the growth of bifidobacteria.

By adulthood, over 400 different species may be present (see Table 17.5) but only the most

abundant bacteria have been well identified, because of limitations in methodology. Resident

bacteria can be found starting with the mouth and working down the GI tract. The stomach and

the upper small intestine may have as many as 10 colony-forming units (CFU/ml), the ileum 10

7, and the colon 1011 to 1012

Anaerobic bacteria outnumber aerobic by a factor of 1000 to 1. The bacteria that reside in the

human intestinal tract have both beneficial and harmful effects on the host. The production of

vitamins, SCFAs, some proteins, the role played in digestion and absorption of nutrients, the

production of protective bacteriocins, and the stimulation of the immune system are all positive

effects of the intestinal microflora. At the same time, intestinal bacteria

produce carcinogens and mutagens directly during their metabolism and also enzymes that

convert digesta contents into carcinogens and mutagens. Products of fermentation such as

ammonia, amines, and phenols may be harmful and some bacteria are pathogenic. Mitsuoka

and Gorbach list the many enzymatic reactions of intestinal bacteria and their impact on health,

disease, and infection. Because of the difficulties in identifying and enumerating various

microorganisms that inhabit the GI tract, several authors have suggested that a more sensitive

and perhaps more relevant approach is to measure effects on the metabolic activities of the

bacterial flora because of their potential impact on metabolism and disease. Carman and

colleagues used the term microflora-associated characteristics (MACs) and argued that changes

in MACs brought about by dietary (probiotic or not) interventions were true indicators of

changes in the intestinal flora, and a more useful way of establishing the consequences of such

changes. Goldin and Gorbach used much the same reasoning when they measured bacterial

enzymes associated with the production of carcinogens in the intestine. Table 17.6 lists the

MACs suggested by Carman and colleagues.Other characteristics could be added that also reflect

changes to the intestinal tract.

IV. PRODUK PROBIOTIK

A. YOGURT

Yogurt merupakan susu fermentasi melalui fermentasi spesifik asam latat, oleh Lb. bulgaricus

dan S. thermophilus. Bakteri lain dapat ditambahkan untuk memperluas properties organoleptis

atau untuk meningkatkan properties probiotik. Yogurt telah ditetiti berperan dalam mengatasi

defisiensi lactase , metabolism kolesterol,imunitas, diare, dan jenis tertentu

1. defisiensi Lactase

Yogurt merupakan suatu produk yang ditoleransi oleh defisiensi lactase (β

-galactosidase). It is more accurate to refer to a lactase deficiency as opposed to a

lactose intolerance. Lactase merupakan enzim digestif terdapat dalam intestine bertanggung

jawab terhadap hidrolisis laktosa susu menjadi glukosa dan galaktosa. Defisiensi lactase A

lactase deficiency results in the buildup of unabsorbed lactose which acts osmotically to

retain water. Defisiensi ditandai dengan diare, excessive flatulence, bloating, dan sakit pada

abdominal perut setelah konsumsi susu atau produk susu.pengukuran aktifitas enzim, konsentrasi

laktosa, glukosa, atau galaktosa dalam digesta, atau dengan pengukuran pernapasan sebagai cara

evaluasi efek treatmen dengan makanan pada aktivitas lactase.

Pada tahun 1984, In 1984, two groups, Kolars and colleagues and Savaiano and colleagues,

48 demonstrated that yogurt reduced the symptoms of lactase deficiency and speculated that this

was due to the live bacteria in yogurt. Yogurt was said to be able to autodigest lactose, resulting

in 20 to 30% lower lactose levels in yogurt compared to unfermented milk when consumed.

Yogurt, but not heat-treated yogurt, improves lactose digestion, indicating that the live bacteria

in yogurt are responsible, and long-term ingestion (8 d) does not seem to change this.49,50 The

bacteria in yogurt survive passage through the stomach due to the enhanced protective

(buffering) properties of the yogurt compared with milk. However, the buffering capacity of

yogurt may also slow hydrolysis until the digesta passes to a point in the intestinal tract where

the pH favors β-galactosidase activity.49 The β-galactosidase activity in commercial yogurts has

been found to vary depending on the manufacturer, whether fruit is added, the addition of

additional bacteria, and whether the yogurt is frozen or not. Frozen yogurt that is pasteurized

before freezing has no β-galactosidase activity. To overcome this, some manufacturers add

starter culture to the pasteurized yogurt before freezing, but this does not necessarily increase

enzyme activity. In addition to the in vivo bacterial hydrolysis, there also appears to be a slower

rate of stomach emptying after a yogurt load compared to milk due to differences in physical

properties. This effect may contribute to the enhanced digestion of the lactose in yogurt.52,53

The beneficial effects of yogurt on healthy individuals may not be as obvious as for those who

have a defined medical problem. Guerin-Danan et al.54 saw few changes in the fecal bacteria

and the bacterial enzyme activity of healthy infants (10 to 18 months old) over a 1-month

supplementation trial. Branch-chain and long-chain fatty acid levels were significantly reduced

during yogurt consumption, however.

TABLE 17.6

Microflora-Associated Characteristics Indicative of Intestinal

Microflora Changes

1. Cellular fatty acid profiles of washed bacteria pellet of fecal or cecal contents

2. Primary to secondary bile acid ratio

3. Ratio of primary to secondary sterols

4. Molar ratio of SCFAs in intestinal material

2. Cholesterol Metabolism

The research into the effects of yogurt consumption on blood cholesterol has been difficult to

understand because of the contradictory results that have been reported over the years. It is now

clear that, in many cases, results and conclusions from one experiment cannot be compared with

those of others because of differences in experimental protocol. The sex, age, general health

status, initial cholesterol level, and level of physical activity of subjects all influence cholesterol

metabolism. The diet before and during the experiment can also influence results, as can the time

of day the yogurt is consumed, whether it is consumed with other food or not, and the position in

the meal (beginning or end of meal). One of the most important details of many yogurt–blood

cholesterol experiments, namely, the type of yogurt fed (including details of the levels and an

unambiguous identification of bacteria in the test yogurt or fermented milk), are often not well

described. This, together with the fact that proper controls for such feeding trials were often not

included, reduces the scientific validity of many studies.

The observation that even though the Masai of Africa ate a diet rich in saturated fats and

fermented milk, they had low blood cholesterol levels (compared with Western standards) and

were free of signs of coronary heart disease, prompted Mann and Spoerry57 to carry out their

much reported study involving fermented milk. Yogurt trials carried out since that time use this

as a starting point, despite of the fact that Mann58 later emphasized that he believed that it was a

milk factor responsible for the hypocholesterolemic effect, which was enhanced by fermentation

to yogurt. Taylor and Williams55 list 12 publications (13 trials) in which yogurt has been fed in

an attempt to lower blood cholesterol. As they point out, many of the study protocols can be

criticized— too few subjects, too short a feeding trial, no or improper control diets, and

unrealistic feeding levels. Of the 13 trials, 8 reported reduced blood total cholesterol levels, 1

reported an increase, and 4 reported no difference from control. Two studies, one showing “no

difference from control” and one showing nonsignificant positive effects on serum cholesterol

levels have been published. Adding oligofructose and two probiotic bacteria to traditional yogurt

(3.5% fat) did not change total serum cholesterol, but did significantly lower the LDL/HDL ratio

in women after consumption for 6 months.61 Feeding healthy residents in a gerontology institute

bioyogurt — yogurt made with Lb. acidophilus, B. bifidum, and Strep. salivarius subsp.

thermophilus — significantly reduced serum cholesterol levels.62

Various suggestions have been made regarding the possible active ingredient(s) or the mode of

action of yogurt, which might affect cholesterol metabolism.63 In vivo cholesterol synthesis may

be related to, and controlled by, the availability of certain short chain fatty acids (SCFAs)

produced by bacteria in the gut; interest has centered on acetate and propionate.64,65 Several

bacteria have been shown to be capable of hydrolyzing bile acids, which would prevent

reabsorption in the intestine and facilitate elimination from the body. Bile acids are formed from

cholesterol in the liver and, therefore, any increase in elimination of bile acids from the body

would increase the rate of conversion of cholesterol to bile acids. It has also been hypothesized

that a reduced pH in the gut as a result of lactic acid produced by some bacteria can cause

cholesterol and deconjugated bile salts to coprecipitate, facilitating elimination of cholesterol

from the body. Until a mechanism is clearly demonstrated, the claim that yogurt or fermented

milk reduces serum cholesterol remains in doubt.

3. Immune Function

The organs of the immune system (spleen, appendix, lymph nodes, Peyer’s patches, etc.) are

varied, but the intestine is generally considered the most important component of the immune

system. A wide variety of parameters, including levels of specific immunoglobulins, numbers of

different cell types, and measurement of specific metabolite concentrations, are used to measure

immune function. To date, several hypotheses have been put forward regarding how yogurt

might improve the immune system. Interaction of the yogurt bacteria with intestinal bacteria

could produce indirect effects, or the gut-associated or systemic immune system might be

affected by metabolites of the bacteria themselves or fermentation products in the yogurt.66

Perdigon’s group67–69 has published several studies using animals that show that yogurt

consumption does improve immune function. Consuming yogurt has also been reported to

modulate some components of the immune system (lymphocytes and CD56 cells) in stressed

individuals. However, Wheeler and colleagues71 measured a wide variety of cellular, humoral,

phagocytic, and mucosal immunity parameters in patients with preexisting atopic disease and

found no significant differences in any parameters whether the patients were consuming yogurt

or milk. Spanhaak and colleagues72 similarly reported no changes in immunity parameters in

healthy subjects who had been fed milk fermented with Lb. casei strain Shirota, even though

fecal bacteria patterns were changed and fecal enzyme activities were significantly decreased.

Gill’s73 review of the literature emphasized the difficulties in comparing the results from

different studies but concluded that there is enough evidence to suggest that certain lactic acid

bacteria, given at adequate levels of intake, can influence immune function in humans.

Additional published data showing positive effects would strengthen this conclusion.

4. Diarrhea

Diarrhea, particularly in young children, can be problematic because of the need to rehydrate the

patient as quickly as possible combined with the problems associated with decreased nutrient

intake. The detrimental consequences of complete withdrawal of food from infants as a treatment

have been defined, but withholding food during early stages of diarrhea is still widespread.74

Fermented milk or yogurt can supply liquid and simultaneously may supply natural antibiotics

produced by the lactic acid bacteria to prevent or reduce the severity of infantile diarrhea.

Gonzalez and colleagues75 showed that milk fermented with Lb. casei and Lb. acidophilus could

be used to prevent the incidence of diarrhea (17% vs. 59% for controls receiving unfermented

milk) in infants 5 to 29 months old, and that the protective effect of the fermented milk appeared

to be correlated to the level of fecal lactic acid bacteria. Isolauri and coworkers76 used milk

fermented with the human strain Lb. casei sp. strain GG to reduce the duration of acute diarrhea

in children. This same strain of bacteria was shown to be effective in the prevention of antibiotic

(erythromycin) associated diarrhea, partly due to its ability to colonize the intestinal tract.77

Yogurt containing Lb. bulgaricus and S. thermophilus and the probiotic strain Lb. casei DN-114

001 has been shown in several large trials with children to significantly reduce the duration of

diarrhea.78,79 However, positive results only appear to be applicable in infants who are

otherwise well nourished.80 A nonsignificant reduction in the incidence of diarrhea in healthy

adults consuming yogurt containing Lb. casei has recently been reported.81

5. Cancer

The beneficial effect of yogurt consumption on reduced cancer incidence is not well established.

The article published by Van’t Veer and colleagues82 is often quoted as proof of a link between

yogurt consumption and a low incidence of breast cancer. Based on a daily food-consumption

questionnaire of newly diagnosed breast cancer patients or a group of healthy women (control),

they concluded that eating fermented milk products (yogurt, buttermilk, Gouda cheese) may have

a protective effect against breast cancer. Two more recent dietary survey studies came to

differentconclusions about the effect of yogurt (fermented milk products) on colorectal cancer.

The work of Goldin and Gorbach45 and Goldin and colleagues85 supports the idea that the Lb.

acidophilus found in yogurt may impact on marker enzymes related to cancer. They found two to

6-fold reductions in the activities of β-glucuronidase, nitroreductase, and azoreductase enzyme

activities after 4-week supplementation with 109 to 1010 viable Lb. acidophilus. These bacterial

enzymes produce carcinogens from procarcinogens in the lower intestine. This work, together

with positive in vitro and experimental animal results, suggests that the bacteria in yogurt may

act directly or indirectly to prevent cancer.86–89 Recent data using mice fed yogurt has indicated

that the immune system may be involved in inhibiting the promotion and progression of

colorectal cancer.90 Other work on the cancer-fighting properties of yogurt has centered on the

isolation and identification of bioactive peptides. Caseins found in milk are themselves

antimutagenic; totally hydrolyzed caseins are not. A wide variety of peptides of various lengths

are formed from milk during fermentation or in the stomach during the digestion of yogurt.91–93

Low-molecular-weight peptides have a wide variety of activities in vitro and in vivo, including

antimutagenic and antitumor properties that may be responsible for the beneficial effects of

yogurt on cancer initiation and progression.

6. A Vehicle for Other Nutrients

The popularity of yogurt has prompted several studies that have investigated the feasibility of

using yogurt as a vehicle for other important nutrients that normally would not be found in

yogurt. Fernandez-Garcia and colleagues94 have recently shown that oat fiber can be added to

plain yogurt and still maintain commercially acceptable sensory qualities. Plant sterols have been

added to yogurt producing a product that significantly lowers serum cholesterol after only three

weeks of consumption.

In spite of the potential problems of off-flavor and encouragement of growth of contaminating

bacteria, Hekmat and McMahon96 were able to produce a yogurt with up to 40 mg/kg of added

iron that was acceptable particularly to untrained consumers. In addition, it has been shown that

yogurt consumption can increase zinc bioavailability in humans eating a diet high in plant-based

phytates without affecting iron bioavailability.

B. KEFIR

Kefir is a fermented milk drink that is believed to have its origins in the Caucasus Mountains of

the former U.S.S.R. Traditionally, it was made from goat or cow milk that was stored in animal

skin bags. Over time, a mass of bacteria, yeasts, proteins, and carbohydrates precipitated out

from the drink and was used to inoculate new milk. This mass is called kefir grains, and it is the

grains that give kefir its texture, taste, and possible health benefits. Kefir has a long oral tradition

for its healthpromoting properties in Eastern Europe and has only recently been produced in

North America on a commercial scale.98 A product of the fermentation process is CO2 gas,

which continues to be produced after packaging and results in a thick drink with a “sparkling”

mouth-feel when consumed.

Unlike yogurt, which requires only two well-defined bacteria for production, the microbiology

of kefir is much more complex (Table 17.7) and has been shown to vary from country to country,

thus making a comparison of its properties difficult. The use of molecular biological techniques

has shown that many bacteria have been misidentified in the past, and the list of bacteria and

yeasts in kefir may not be as long as once believed.99 Changes that occur during fermentation

promote the growth of certain microorganisms, while reducing the growth of others. Therefore,

reports of the composition and properties of the grains may not be totally applicable to the

finished product.

1. Fabrication

TABLE 17.7

Microorganisms Reported to Be Found in Kefir and Kefir Grains Bacteria

Three different types of kefir drink are produced — traditional kefir, Russian-type kefir, and

industrial kefir — depending on whether the grains or a mother culture from the grains is used to

inoculate the pasteurized milk.103,104 No studies have been published that compare the

properties (health benefits or otherwise) of kefir produced by different processes. Incubation is

carried out at 20 to 22°C for 18 to 20 h until a specific pH is reached and then packaged, or a

maturation period can be introduced. The grains themselves have a strong yeasty taste and,

therefore, using a mother culture or sieving out the grains may be ways of making a product

closer to buttermilk in taste.

A double-fermentation process was proposed by Marshall and Cole105 as a way of making the

taste of traditional kefir more acceptable to the consumer.106 Today, commercial kefir is only

produced from cow milk, but other milks, including soymilk, can be fermented with kefir grains.

Studies of the microflora of kefir grains led to the formulation of less complex starter cultures

that could replace kefir grains. A method using as few as four bacteria and one yeast type has

been reported as being used to produce “kefir.”109 However, apart from very gross

characteristics, there is little reason to believe that the two beverages (produced from traditional

grains or simpler starter cultures) are the same. Today, lyophilized kefir starter culture mixtures

are used by some manufactures instead of kefir grains.

2. Health Benefits

The (Western) scientific literature to support the beneficial health claims of kefir is not extensive

and few human feeding trials using kefir have been performed. The Russian literature lists peptic

ulcers, biliary tract diseases, chronic enteritis, bronchitis, and pneumonia as all being treated with

kefir.98 Kefir is included as a regular part of hospital diets, is a recommended food for nursing

mothers, and is often used as an initial weaning food for babies in Russia. Both kefir grains and

the drink itself have been shown to have antitumoral, antibacterial, and antifungal properties that

may explain the diverse list of diseases and infections it is used to treat. In the tests carried out by

Cevikbas and colleagues,110 the kefir grains were more effective than the drink. Osada and

coworkers reported the isolation of a sphingomyelin from kefir grains, which they showed

enhanced interferon-β production in a human cancer cell line that had been challenged with a

chemical inducer. They concluded that this sphingomyelin could be important in treating viral

diseases. Several Japanese studies using experimental animals have indicated anticancer

properties of kefir for a variety of cancers.111–117 These studies have used kefir grains, kefir-

grain polysaccharides, or both to prevent the onset of cancer if given before a cancer challenge or

to slow the growth and spread of cancer if given after the cancer challenge. However, to date,

such experiments have not been carried out on humans.

Vujicic and colleagues118 incubated milk samples with kefir grains from six different sources

and showed that after 24 h, between 22 and 63% of the cholesterol originally in the milk was

assimilated. They concluded that the grains possessed a cholesterol-degrading enzyme system. In

a study in which hypercholesterolemic men were given 500 ml of kefir daily for 1 month, no

changes (compared with values obtained after 1 month of milk feeding) were measured in serum

cholesterol levels or cholesterol metabolism, despite the fact that a reference organism (Lb.

brevis) could be found in fecal samples and changes in fecal volatile fatty acids were found.119

V. FERMENTED VEGETABLES AND OTHER FOODS

The most well-known and popular probiotic foods in industrialized countries are milk based.

Yakult®, a milk product containing the probiotics bacteria L. casei Shirota, is believed to be the

largest-selling probiotic product in the world. However, fermented foods are produced and

consumed around the world based on vegetables, fruits, cereals, grains, root crops, fish, and

meat. Some of these foods may have health-promoting properties. Fermentation is often

considered an effective method to preserve vegetables, without regard to any health benefits.

Reddy and colleagues121 list 23 legume-based fermented foods, the majority

of which are soybean products. Only natto, a popular fermented soybean product from Japan, is

mentioned as encouraging the growth of Bifidobacterium in animals. Most reports of fermented

vegetables have centered on the organism(s) used to produce the fermentation and on any

increases in the protein, amino acid, and vitamin concentrations of the final product, not any

possible probiotic effects.

Various other foods have been tested as possible vectors to carry probiotic bacteria. Verification

of the efficacy of these products has not been given much attention to date, but, rather,

investigation of whether the bacteria will survive in the food matrix and during processing and

storage. Cheddar cheese containing Enterococcus faecium,126 B. longum in frozen yogurt,127

and B. longum, B. infantis, B. brevis,32 L. acidophilus, and B. bifidum125 in ice cream are

examples. Lee and Salminen6 predicted that probiotic infant formulae, baby food, fermented

fruit juices, fermented soy products, cereal-based products, as well as disease-specific products,

are possible products of the future.

VI. THE FUTURE FOR PROBIOTICS AND PREBIOTICS

The market for probiotic and prebiotic products will continue to grow as our knowledge of the

intestinal microflora and its role in the maintenance of health and disease resistance advances.

Food manufacturers will have to be able to commercialize products that maintain viable bacteria

up until the time of consumption, and in many cases, will also have to provide encapsulation or

other protective mechanisms for the live microorganisms in their products to be able to deliver

bacteria to the correct site of action in the GI tract.