(Special Notes: For introduction and Background of this post, please follow the previous post... Thank you! )
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
• 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
• 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).
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;
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
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.
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