HEALTH BENEFIT AND FOOD APPLICATION OF PREBIOTICS

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HEALTH BENEFITS OF PREBIOTICS

The following effects of prebiotics have been claimed:

• relief of constipation
• reduce intestinal pH
• increase in mineral absorption
• restore intestinal bacterial balance
• effect blood cholesterol level
• reduce risk on colorectal cancer
• effects on the immune system
• better intestinal flora in infants

Prebiotics may restore intestinal balance after a disturbance due to antibiotics, diarrhoea, stress or other drugs (non antibiotics). By either selectively stimulating a certain group of bacteria the balance can be restored. This may be possible for many different bacterial groups. This can be either by direct stimulation (the selected bacteria grow on the prebiotic) or by indirect stimulation (the bacteria create a favourable environment for other bacteria). In this case both selective stimulation and changes in metabolism play a role.

Promotion of Normal Colon Transit Time

Constipation is an exceedingly common clinical problem affecting large segments of the population including the elderly, pregnant and nursing women, people on weight loss diets, and people wit disrupted daily schedules such as variable shift workers and business travelers.Prebiotics increase fecal bulk and optimize stool consistency primarily by increasing fecal microbial mass. This increase in fecal bulk stimulates passage through the colon, shortening transit time. Colonic water resorption is reduced, stool becomes softer and heavier, and stool frequency increases. Together these factors alleviate constipation and improve colon evacuation.

Effects of Prebiotics on Mineral Absorption

There is extensive evidence in experimental animals that prebiotics, such as inulin-type fructans, can increase the absorption of a variety of minerals, including calcium, magnesium, iron, and zinc and that they may act through several possible mechanisms. A variety of mechanisms have been proposed to explain the effect of prebiotics on calcium absorption , although themost widely favored explanation concerns their effect on passive calcium absorption in the large intestine. This theory states that non absorbed prebiotics enter the large intestine undigested where they are fermented in to short chain (volatile) fatty acids such as acetate, butyrate, and propionate. These fatty acids lower the pH of the large intestine contents, increase solubility of calcium(and other minerals) in the luminal contents and so increase passive concentration-dependent calcium absorption in the colon. Some animal studies have shown beneficial effects of prebiotics on absorption of other minerals, such as iron  zinc , and copper , although human data are more limited , However, there are little good data on possible mechanisms.

Enhancement of the Immune System

The immune system operates as an organization of functionally specialized cells and molecules to protect the body against foreign substances and invading organisms, acting systemically. Food and nutrients modulate immune functions in multiple ways. The impact of nonessential food constituents on the immune system such as prebiotics and similar complex carbohydrates, however, has been on the study . For proper functioning of the immune system, the intestinal flora also plays an important role. Composition and metabolic activity of the intestinal flora are directly depending on dietary constituents (including prebiotics). Prebiotics itself will have no effect on the immune system. However, by changing the intestinal flora, the immune system may be influenced.  

 Potential Mechanisms of Prebiotic-Induced Immune Alterations

• Selective increase/decrease in specific bacteria that modulate cytokine and antibody

production

• Increase in intestinal SCFA production and enhanced binding of SCFA to G-coupled

protein receptors on leukocytes

• Partial absorption of prebiotics resulting in local and systemic contact with the immune

system

• Interaction of prebiotics with carbohydrate receptors on leukocytes

The gastrointestinal tract is one of the most important components of the body’s defensive system. In addition to providing non-specific protection in the form of a physical barrier against toxins and pathogenic organisms, the intestinal tract also provides specific protection in the form of gut-associated lymphoid tissue, or GALT. GALT represents the largest immune organ in the body and consists of a highly complex network of aggregated and non-aggregated immune

cells. Research indicates prebiotics modulate both intestinal and systemic immunity largely through their association with gut microflora. Prebiotic support of health-promoting intestinal microorganisms leads to increased competition with pathogens for colonization sites, up regulated GALT expression of secretory IgA and immune-stimulating cytokines, and enhanced production of short chain fatty acids and other antimicrobial substances that create an inhospitable environment for pathogen growth. Prebiotics such as inulin, inulin-type fructans, galactooligosaccharides, and lactulose have been shown to enhance colonization resistance against a variety of enteropathogenic organisms, including Clostridium difficile, Clostridium perfringens, E. Coli and other coliforms.

Influences on Glucose & Insulin Levels

Evidence suggests prebiotics can favorably influence serum glucose and insulin levels in a variety of ways. Inasmuch as they may replace starches and/or sugars in foods,DGOs and other prebiotics can reduce the amount of glucose available for absorption into the bloodstream. Prebiotics may also prevent excessive blood glucose elevations after a meal by delaying gastric emptying and/or shortening small intestine transit time. Bacterial fermentation yielding short-chain fatty acids is another mechanism whereby prebiotics can modulate glycemia and insulinemia.

Helps in Lipid Metabolism:

Triacylglycerols (TAGs) and cholesterol are quantitatively the most important circulating lipids (transport and storage of energy). Both have important physiological roles and abnormalities in their metabolism are implicated in major pathologies such as obesity, insulin resistance, type 2 diabetes, dyslipidemia, and atherosclerosis. Concerning hypocholesterolemic effect of prebiotics, several mechanism have been proposed, which are often related to a modulation of bile acid intestinal metabolism, but other properties (e.g., steroid-binding properties) are evoked, which are independent of the fermentation of the prebiotic in the lower intestinal tract.

I Prebiotics as a Potential Treatment against Atherosclerosis

iiPrebiotics as Modulators of Lipid Metabolism Disorders

iii Prebiotics as Potential Treatment against Obesity

Several oligosaccharides which respond to the definition of prebiotics exhibit interesting effects on lipid metabolism. Changes in intestinal bacterial flora composition or fermentation activity could be implicated in modulation of fatty acid and cholesterol metabolism. (specific gelling characteristics of inulin allows the development of low-fat foods without compromising taste or texture This is particularly successful in spreadable products such as table spreads, butter-like

products, cream cheeses and processed cheeses)

Reduction of Risk of Carcinogenesis

Colon cancer is one of the major neoplastic diseases with the number of new cases per year rising rapidly since 1975. Colon cancer is the fourth commonest form of cancer. Various studies shows prebiotics have significant role in preventing colon carcinogenesis. This may be due to various effects of prebiotic such as :

-       Apoptosis and Proliferation

-       Modulation of Immune Response

-       Reduction of Enzyme Activity

In vitro and animal studies have revealed the potential of prebiotics to enhance detoxification processes in colon cells, reduce toxic metabolite production in the gut, and protect against colonic tumor development.

.Prebiotics and Infant Nutrition

The bacterial composition in the infant digestive tract (also called the intestinal microflora) follows a pattern of change starting in the newborn, and may vary depending on the infant diet. Development of the infant’s intestinal microflora is initiated at birth. The aseptic, or sterile, digestive tract of the fetus is inoculated with bacteria during birth by the environment and mother's intestinal and vaginal microflora. Breastfeeding is the gold standard for infant nutrition. Human milk oligosaccharides (HMOs) comprise part of the functional ingredients of human milk. As for most of the components of mother’s milk, the quantity of HMOs differs between mothers, and also during lactation and breastfeeding.In general, breastfed infants have been shown to have higher levels of bifidobacteria than formula-fed infants (Orrhage and Nord 1999). The increased presence of these beneficial bacteria is at least partly due to substances found in human breast milk, especially the HMOs (Coppa et al 2004). The intestinal microflora of the formula-fed infant may differ from that of the breastfed infant (Harmsen et al 2000). While human milk-fed infants have an abundance of bifidobacteria in the gut, formula-fed infants may have a more diverse gut flora, similar to that seen in adults. Formula-fed infants also have a higher risk of intestinal infections.

 Efforts to replicate the immunoprotective and bifidogenic effects of human breast milk on the intestinal tract of bottle-fed infants have led to research examining the effects of incorporating prebiotics into infant formulas. Formulas containing a mixture of galactooligosaccharides and fructooligosaccharides in a ratio of 9:1, have been shown to promote a microflora in infants similar to that seen in breast-fed infants (Stephen Olmstead, MD, David Wolfson). The addition of prebiotics to infant formula can increase beneficial bacteria in the digestive system to levels similar to those in the breastfed baby (Ben et al 2004). In addition, prebiotics can help soften stools to be more like those of the breastfed infant (Costalos et al 2008; Ben et al 2004; Moro et al 2002).

Various health benefits of prebiotics

FOOD APPLICATION OF PREBIOTICS

Prebiotics show both important technological characteristics and interesting nutritional properties. Several are found in vegetables and fruits and can be industrially processed from renewable materials. In food formulations, they can significantly improve organoleptic characteristics, upgrading both taste and mouthfeel. Many are already successfully used in a broad range of food applications . Prebiotics can be used for either their nutritional advantages or technological properties, but they are often applied to offer a double benefit: an improved organoleptic quality and a better-balanced nutritional composition . Food applications are illustrated below;

Application Functionality:

v  Dairy products (yoghurts, cheeses, desserts, drinks) à Fat or sugar replacement, body and mouthfeel,foam stabilization, fiber, and prebiotic

v  Frozen desserts àFat or sugar replacement, texture and mouthfeel, melting behavior.

v  Fruit preparations à Sugar replacement, synergy with intense sweeteners, body and mouthfeel, fiber and prebiotic

v  Breakfast cereals and extruded snacks àSugar replacement, crispiness and expansion, fiber, and prebiotic

v  Baked goods and breads à Sugar replacement, moisture retention, fiber, and prebiotic

v  Fillings à Fat or sugar replacement, texture, and mouthfeel

v  Tablets and confectionery à Sugar replacement, fiber, and prebiotic

v  Chocolate à Sugar replacement, heat resistance and fiber

v  Dietetic products and meal replacersà  Fat or sugar replacement, synergy with intense sweeteners, body and mouthfeel, fiber, and prebiotic

v  Table spreads and butter products à Fat replacement, texture and spreadability, stability, fiber, and prebiotic

v  Salad dressingsà  Fat replacement, mouthfeel, and body

v  Meat products à Fat replacement, texture and stability, and fiber

VII. CONCLUSION:

The intestinal microbiota provides the human host with an array of health benefits. Microfloral organisms act as a functional barrier against colonization by pathogens, promote normal gastrointestinal function, contribute to energy production, and exert enteric and systemic immunomodulatory activity. Support for the health of intestinal flora can take the form of supplementation with living probiotic organisms or prebiotic substances that nourish beneficial endogenous species. Prebiotics are digestion-resistant carbohydrates that selectively stimulate the growth and activity of health-promoting microorganisms such as bifidobacteria and lactobacilli. Major prebiotics include inulin,inulin-type fructans, galactooligosaccharides, and lactulose. Prebiotics taken alone or with probiotics, as in a symbiotic supplement, contribute to the integrity of the gut barrier, help normalize colonic motility, improve nutrient bioavailability, enhance gastrointestinal and systemic immunity, and may favorably modulate blood sugar and lipid levels. Numerous studies in both animals and humans have demonstrated the health benefits of prebiotics. Prebiotic use in nutritional supplements and functional foods is rapidly gaining wide acceptance.

REFERENCES

v  S. S. Biradar, B. M. Patil & V. P. Rasal : Prebiotics For Improved Gut Health . The Internet Journal of Nutrition and Wellness. 2005 Volume 2 Number 1

v  Stephen Olmstead, MD, David Wolfson, ND, Dennis Meiss, PhD, Janet Ralston, BS, Understanding prebiotics

v  R.Gibson and B.Roberfroid, Handbook of Prebiotics

v  R.Gibson and B.Roberfroid, Dietary Modulation of the Human Colonie Microbiota: Introducing the Concept of Prebiotics

v  Sharon Donovan, Glen Gibson ,David Newburg, Prebiotics in Infant Nutrition

INTRODUCTION OF PREBIOTICS

I.                  BACKGROUND

     A complex community of microorganisms inhabits the mammalian gastrointestinal tract from mouth to anus, but the colon is, by far, the main site of this microbial colonization. As a consequence, progress in biology, physiology, and nutrition has considerably broadened our view of the function and the pathophysiological roles of the intestine, especially the large bowel. This organ is no longer viewed solely as a storage vessel that produces feces and eventually absorbs water and a few other simple molecules of both nutritive and endogenous origin. Indeed, recent researchs has convincingly shown that the large bowel and its microbiota form a strong symbiotic association and interact with each other to play major roles not only in colonic function but also in whole body physiology including endocrine activities, immunity, and even brain function.

Bifidobacteria and Lactobacillus live in great concentrations at the lower region of the small intestine and predominantly in the large intestine. These beneficial bacteria take a role as guards against harmful microbes living in the large intestine, keeping them from invading the small intestine. The small intestine functions to digest and absorb the majority of nutrients. When the body's immunity declines the risk of infection increases, it is essential to keep the immune capacity high for preventing or decreasing infection. Bifidobacteria and Lactobacillus have recently been shown to increase gut and overall immunity.

There are several aspects of an individual's health and diet that can adversely affect the gut microflora. High levels of fat in the diet can negatively affect the level of Bifidobacteria in the gut, as these beneficial bacteria are sensitive to increased levels of faecal bile acids, which are directly related to the amount of fat in the diet. Fatty diets may increase the amounts of bile acids in the faeces, and consequently increase their inhibitory effect to Bifidobacteria. The nature of the diet may also indirectly influence the gut conditions, which affect the activity of Bifidobacteria. Disorders of gastric function or intestinal motility may disturb the normal microbial balance.

Numerous studies have shown that an imbalance of friendly to unfriendly gut bacteria (too few friendly bacteria) can cause or aggravate various health conditions. Moreover, supplements aimed at increasing the number of friendly bacteria have been shown to help combat many types of diarrhea, irritable bowel syndrome, eczema, ulcerative colitis; reduce the incidence of canker sores and vaginal yeast infections; and exert positive effects on the immune system. Friendly gut bacteria consist of Lactobacillus acidophilus, L. bulgaricus,L. reuteri, L. plantarum, L. casei, B. bifidus, S. salivarius, S. thermophilus and the yeast Saccharomyces boulardi.

II. OBJECTIVES

The main objective of this paper is to showcase :

1.      Brief introduction of prebiotics

2.      Health benefits of prebiotics

3.      Prebiotics in food applications

III. INTRODUCTION

     The term “prebiotic” was coined in 1995 by Gibson and Roberfroid,although prebiotics were recognized as early as the 1950s when György and coworkers described “bifidus factor”, a bifidogenic substance that selectively promoted the growth of bifidobacteria (called Lactobacillus bifidus at that time). Human milk and colostrums were found to contain large amounts of “bifidus factor”. In the 1970s and ’80s, Japanese investigators pioneered the use of digestion-resistant saccharides to favorably modify the intestinal microbiota using fructooligosaccharides, galactooligosaccharides, and lactulose The 1980s and ’90s saw a marked increase in the use of probiotics to favorably modify the intestinal microbiota and a concomitant growth in interest in using prebiotics to achieve the same goal. In contrast to the probiotic strategy for microflora modification by providing living microorganisms, the prebiotic strategy seeks to stimulate the growth and/or enhance the metabolic activity of the healthful bacteria already colonizing the intestines. Prebiotics offer the ability to enhance the healthful strains in a person’s unique community of bacteria including beneficial strains not available as probiotics, such as Eubacterium species.

In 1995, Gibson and Roberfroid defined a prebiotic as a “nondigestible food ingredient that beneficially affects the host by selectively stimulating the growth and/or activity of one or a limited number of bacteria in the colon, and thus improves host health.” This definition only considers microbial changes in the human colonic ecosystem.Later, it was considered timely to extrapolate this into other areas that may benefit from a selective targeting of particular microorganisms and to propose a refined definition of a prebiotic as (Gibson et al.2004): “a selectively fermented ingredient that allows specific changes, both in the composition and/or activity in the gastrointestinal microflora that confers benefits”

By definition, a prebiotic classifies as a specific colonic nutrient. Most potential prebiotics are carbohydrates, but the definition does not exclude non-carbohydrates to be used as a prebiotic. Accordingly, the key characteristics that serve as criteria for classification of a compound as prebiotics are resistance to digestive processes in the upper part of the gastro intestinal tract and selective fermentation by one or a limited number of the microorganisms in the intestinal microbiota, especially the colonic microbiota, thus giving these a proliferation advantage and consequently modifying the microbiota composition.

In order for a food ingredient to be classified as a prebiotic , it must :

 1) be neither hydrolyzed nor absorbed in the upper part of the gastrointestinal tract.

 2) be a selective substrate for one or a limited number of beneficial bacteria commensal to the colon which are stimulated to grow and/or are metabolically activated.

3) consequently, be able to alter the colonie flora in favor of a healthier composition.

4) induce luminal or systemic effects that are beneficial to the host health.

Prebiotics can be classified as a type of digestion-resistant carbohydrate or dietary fiber. Like all fibers, prebiotics resist breakdown by human digestive secretions and arrive relatively unchanged in the lower regions of the intestinal tract where they can be utilized as an energy source by the resident microflora. What distinguishes prebiotics from other fibers is that prebiotics by definition selectively stimulate the growth of only beneficial microfloral organisms such as lactobacilli and bifidobacteria. A number of important dietary fibers like cellulose and pectin fail to meet this definition. Prebiotic properties have been ascribed to many types of carbohydrates, but they have been best documented for digestion-resistant oligosaccharides (DGOs).

DGOs include

- inulin-type fructans

- galactooligosaccharides

-lactulose

-isomaltooligosaccharides

-xylooligosaccharides

-soy-oligosaccharides

-gentiooligosaccharide

-nigeroligosaccharides (Stephen Olmstead, MD, David Wolfson)

Most prebiotics and prebiotic candidates identified today are nondigestible oligosaccharides. They are obtained either by extraction from plants (e.g.,chicory inulin), possibly followed by an enzymatic hydrolysis (e.g., oligofructose from inulin) or by synthesis (by trans-glycosylation reactions) from mono- or disaccharides such as sucrose (fructooligosaccharides) or lactose (trans-galactosylated oligosaccharides or galactooligosaccharides) .

IV.COMMONLY USED PREBIOTICS

Inulin-type Fructans:

The prebiotic effects of inulin-type fructans are well-established. Inulin-type fructans are linear DGOs composed of fructose moieties linked by β(2à1) bonds. Inulin is arbitrarily defined as a mixture of oligosaccharides with chain lengths of 2-60 fructose molecules, with or without an initial glucose. Inulin-type fructans are storage carbohydrates commonly found in wheat, onions,asparagus, bananas, garlic, artichokes, and leeks. Inulin-type fructans have their greatest effect on intestinal Bifidobacterium populations

Galactooligosaccharides:

Galactooligosaccharides are digestion-resistant oligosaccharides naturally found in both human and cow’s milk. They can also be derived from specific microbial fermentation of lactose or synthesized using the enzyme β-galactosidase and lactose syrup. Galactooligosaccharides selectively augment Bifidobacterium and Lactobacillus numbers within the human intestinal microbiota. Prebiotic applications of galactooligosaccharides are of great interest because of their natural occurrence in human milk. Administration of galactooligosaccharides to formula-fed infants has been shown to engender an intestinal flora similar to that of breast-fed infants

Lactulose:

Lactulose is synthetic galacto-fructose made by the isomerization of lactose. Although technically a disaccharide, lactulose is generally grouped together with the DGOs. Lactulose is not usually present in nature although very small amounts may be found in heat-treated milk products as a result of non-catalyzed isomerization.. The β(1à4) bond in lactulose cannot be split by human intestinal enzymes and is preferentially metabolized by colonic lactic acid bacteria with lactate and short-chain fatty acids as major end products with with significant increases in Bifidobacterium and Lactobacillus numbers and reductions in Clostridium perfringens, Bacteroides, Enterobacteriaceae, and Streptococcus populations

Fig: Different prebiotics