(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
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).
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