|Year : 2012 | Volume
| Issue : 1 | Page : 3-6
Prebiotics and their benefits on human health
Rector, Dr. NTR University of Health Sciences, Vijayawada, India
|Date of Web Publication||21-Mar-2012|
M V Ramanamma
Rector, Dr. NTR University of Health Sciences, Vijayawada
Source of Support: None, Conflict of Interest: None
Prebiotics are necessary additives to diet, which have a positive influence on human health. Top foods containing prebiotics are chicory root, garlic, onion, wheat bran, etc. Prebiotics are of the nature of oligosaccharides and are nondigestible dietary fiber, which reach up to the colon to be utilized as substrates by the useful gut microflora, namely Lactobacilli and bifidobacteria. This results in further multiplication of these bacteria, which prevent colonization by enteric pathogens. Apart from this, several other beneficial effects due to prebiotics are documented: Increase in calcium absorption, potentiation of the immune system, reduction of risk of colorectal cancer and other inflammatory bowel disorders, antihypertensive effect, reduction of constipation, reduction of obesity, antidiabetic effect, etc. All these are attributed to increased production of short-chain fatty acids by the stimulated beneficial bacteria. As prebiotics are heat stable, they can be added to daily food choices like cereals, bread, biscuits, drinks, etc., converting them into functional foods. Addition of both prebiotics and probiotics to foods makes better functional foods. These foods are called synbiotic functional foods. Benefits of prebiotics are still being explored. There is a need to spread knowledge of prebiotics among the elite as well as general public, considering their beneficial effects on health.
Keywords: Prebiotics, beneficial effects, short-chain fatty acids, functional foods, synbiotic foods
|How to cite this article:|
Ramanamma M V. Prebiotics and their benefits on human health. J NTR Univ Health Sci 2012;1:3-6
| Introduction|| |
The influence of nutrition on human health is well documented. In spite of availability of plenty of literature, there is still ignorance among the elite, as well as the illiterate, about some of the important requirements in diet, which help human health in many ways. This article aims to enlighten about one of the necessary additives to diet, namely prebiotics.
| Definition|| |
The classical definition of prebiotics was given by Gibson and Roberfroid , who, in the year 1995, defined them as nondigestible food components, usually oligosaccharides, which evade digestion by human enzymes, reach the colon in an intact state, and are fermented by beneficial indigenous microflora of the intestine.
The selective fermentation of prebiotics by the gut microflora results in a healthier composition of gut microflora and significant luminal and systemic effects, which are beneficial to the host's well-being and health.
| Prebiotics, Dietary Fiber, and Colonic Foods|| |
Prebiotics are nondigestible dietary fiber. The most prevalent forms of prebiotics are nutritionally classed as soluble fiber. Colonic foods are those, which pass undigested into the colon to serve as substrates for the endogenous colonizing colon bacteria. Generally resistant starch and non-starch polysaccharides are classified as "colonic foods" but not as prebiotics, as they are not metabolized by the gut microflora.
A prebiotic can be a fiber but a fiber need not be a prebiotic. 
| Properties and Function|| |
Typically, prebiotics are carbohydrates. Short-chain saccharides ferment more quickly and long-chain saccharides ferment slowly. Prebiotics get fermented in the colon and in the acid pH so produced, increase the number and/or activity of bifidobacteria and lactobacilli. The importance of the bifidobacteria and the lactic acid bacteria is that these groups of bacteria have several beneficial effects on the host, especially in terms of improving digestion (including enhancing mineral absorption) , and the effectiveness and intrinsic strength of the immune system.
Prebiotics are heat resistant, which keep them intact during the baking process and allow them to be incorporated into every day food choices. 
| Sources|| |
Traditional dietary sources of prebiotics include soybeans and inulin sources like onion, garlic, chicory root, raw oats, unrefined wheat, unrefined barley, etc. Some of the prebiotics that naturally occur in breast milk are believed to play an important role in the development of a healthy immune system in infants.
Top foods containing prebiotics are: Raw chicory root (64.6%), raw garlic (17.5%), raw onion (8.6%), cooked onion (5%), raw wheat bran (5%), and cooked whole wheat flour (4.8%).
Classification of some naturally occurring and synthetic prebiotics and their sources are given in the [Table 1] below. 
| Effects of Prebiotics on Health|| |
It has been argued that many of the positive health effects of prebiotics emanate from increased production of short-chain fatty acids (SCFA) by the stimulated beneficial bacteria. The following are some of them.
- Increase of useful gut flora, which synthesize B complex vitamins: Prebiotics serve as food for the colonic microflora, which proliferate and synthesize the useful B complex vitamins.
- Positive effects on calcium and other mineral absorption:  Prebiotics help in acidification of the gut lumen by the SCFA, thereby increasing solubility of the minerals in the gut, increased expression of calcium binding proteins mainly in the large intestine, modulated expression of bone-related cytokines, increased bioavailability of phyto-estrogens, and increased calcium uptake by enterocytes.
- Increase in the effectiveness of the immune system:  The knowledge about the influence of prebiotics on the gut-associated lymphoid tissues (GALT) for the improvement of human health is still growing. There is convincing preliminary data to suggest that the consumption of prebiotics can modulate immune parameters in GALT, secondary lymphoid tissues, and peripheral circulation.
- Reduction of risk of colorectal cancer: , The ingestion of probiotics, prebiotics, or combination of both (synbiotics), alter the intestinal microflora by increasing concentrations of beneficial bacteria such as lactobacillus and bifidobacteria, and reducing the levels of pathogenic micro-organisms. This strategy has the potential to inhibit the development and progression of neoplasia via mechanisms including decreased intestinal inflammation, enhanced immune function and anti-tumorigenic activity, binding to potential food carcinogens including toxins found in meat products, and a reduction in bacterial enzymes which hydrolyze pre-carcinogenic compounds, such as beta-glucuronidase.
There is substantial experimental evidence to suggest that prebiotics can influence the development and progression of colorectal cancer and may be beneficial in the prevention and treatment, However, to date there have been few conclusive human trials.
- Reduction of risk of inflammatory bowel disorders (Crohn ' s Disease and ulcerative colitis):  It has been argued that prebiotics are beneficial to Crohn's disease through production of SCFAs to nourish the colon walls, and beneficial to ulcerative colitis through reduction of hydrogen sulfide gas due to reduction of sulfate-producing bacteria, which do not thrive in the slightly acidic environment created by SCFAs.
- Antihypertensive effect  and regulation of blood cholesterol: [ 14], One of the possible mechanisms is via the lowering of blood lipid and cholesterol. The lipid and cholesterol-lowering effects of prebiotics could be attributed to the production of SCFAs. The SCFA produced by prebiotics in the large bowel are absorbed in the portal vein, and a major part is metabolized by the liver and subsequently affects various metabolic processes, resulting in lowering of blood pressure. Indigenous lactic acid bacteria and bifidobacteria often have the ability to ferment prebiotics and produce lactates and acetates as the main metabolites, with smaller amounts of propionate and butyrate. It has been reported that propionate could hinder fatty acid and cholesterol synthesis, while lactate produced in the colon plays a significant role in lowering the synthesis of triacylglycerol fatty acids.
Prebiotics absorb fat and phospholipids in the lower intestines, leading to increased excretion in feces. Cholesterol levels have been reported to be reduced via the binding effect of prebiotics. The reduction of total cholesterol regulates the receptors of low-density lipoprotein (LDL) and thus increases the clearance of LDL cholesterol. This overall cholesterol-lowering effect could reduce the stiffness of large arteries and thus could potentially reduce blood pressure.
- Maintenance of regularity of bowel:  Prebiotics reduce constipation. The laxative effects of prebiotics are attributed to their action as soluble nondigestible fibers. Some researchers have suggested that a reduction in the number of bifidobacteria has been related to constipation, and treatment to correct this with prebiotics could therefore benefit bowel function.
- Enhancement of bacteriocin synthesis by lactobacilli ,  resulting in a lower incidence of enteral infections by pathogenic bacteria.
- Reduction of obesity:  Past studies involving animals models (mainly rats) have shown promising evidence that ingestion of inulin-type fructans could regulate body weight via the promotion of endogenous glucagon-like peptide-1 (GLP-1) in the gut. GLP-1 is a key hormone released from enteroendocrine-L cells in response to nutrient ingestion and is the key modulator of food intake by promoting satiety. This consequently reduces the intake of food, which leads to a decreased in body weight and BMI.
- Antidiabetic effect: Giaccoa et al.,  evaluated the effect of short-chain fructo-oligosaccharides (prebiotics) on glucose tolerance in 30 volunteers. The randomized, double-blind, placebo-controlled, and crossover trial for two months showed that daily consumption of 10 g/day of short-chain-fructo-oligosaccharides contributed to a significant (P<0.02) reduction of postprandial insulin response as compared to those in the placebo group, which did not show any significant differences.
In fact, the benefits of consuming both prebiotics and probiotics are so strong that synbiotic products (products in which both a probiotic and a prebiotic are combined) are being developed as functional foods.  If all consumers met their dietary requirements, and ate 5-8 servings of fruits and vegetables per day, then their dietary fibre needs would be met. However, the vast majority of the population does not meet these requirements by consuming fruits and vegetables alone. Functional foods increase consumer choice by adding prebiotics to everyday food items. By continuing to eat and drink common foods, but choosing functional alternatives (eg, bread containing prebiotics), dietary requirements can be met without significant changes to food preferences.  As the need for functional foods rises, prebiotics are being added to many everyday food choices such as cereals, biscuits, breads, table spreads, drinks, and yoghurts.
The addition of prebiotics to diet should be gradually increased. Immediate addition of substantial quantities of prebiotics to the diet may result in a temporary increase in gas, bloating, or bowel movement. It may also impair nutrient absorption and temporarily increase colonic transit time. 
Future research areas 
It is recognized that numerous potential new applications are being considered for prebiotic use, as mentioned below.
Prevention and or management of type 2 diabetes mellitus; drug bioavailability; effects on autoimmune diseases and allergy, modulation of pathogenic biofilms, and alleviation of physiological and psychological symptoms of stress and anxiety.
| References|| |
|1.||Roberfroid MB. Prebiotics: The concept Revisited. J Nutr 2007;137:830. |
|2.||Available from: http://www.dairyforall.com/prebiotic.php. [accessed on 2012]. |
|3.||Available from: http://www.fao.org/ag/agn/agns/files/Prebiotics_Tech_Meeting_Report.pdf. [accessed on 2012]. |
|4.||Coxam V. Current data with inulin-type fructans and calcium, targeting bone health in adults. J Nutr 2007;137:2527. |
|5.||Stephanie S, Bernhard W. Inulin and Oligofructose: Review of Experimental Data on Immune Modulation. J Nutr 2007;137:2563. |
|6.||Available from: http://www.prebiotic.ca/prebiotic_fibre.html. [accessed on 2012]. |
|7.||Available from: http://www.dairyforall.com/prebiotic.php. [accessed on 2012]. |
|8.||Katharina E, Scholz A, Jürgen S. Inulin and Oligofructose and Mineral Metabolism: The Evidence from Animal Trials. J Nutr 2007;137:2513. |
|9.||Lomax AR, Calder PC. Prebiotics, immune function, infection and inflammation: A review of the evidence. Institute of Human Nutrition, School of Medicine, University of Southampton, Tremona Road, Southampton, UK. www.ncbi.nlm.nih.gov/pubmed/18814803. |
|10.||Geier MS, Butler RN, Howarth GS. Probiotics, prebiotics and synbiotics: A role in chemoprevention for colorectal cancer? Cancer Biol Ther 2006;5:1265-9. |
|11.||Munjal U, Glei M, Pool-Zobel BL, Scharlau D. Fermentation products of inulin-type fructans reduce proliferation and induce apoptosis in human colon tumour cells of different stages of carcinogenesis. Br J Nutr 2009;102:663-71. |
|12.||Hedin C, Whelan K, Lindsay JO. Evidence for the use of probiotics and prebiotics in inflammatory bowel disease: A review of clinical trials. Proc Nutr Soc 2007;66:307-15. |
|13.||Yeo SK, Ooi LG, Lim TJ, Liong MT. Antihypertensive Properties of Plant-Based Prebiotics: School of Industrial Technology, Universiti Sains Malaysia, 11800 Penang, Malaysia. |
|15.||Fernandez ML. Soluble fiber and nondigestible carbohydrate effects on plasma lipids and cardiovascular risk. Curr Opin Lipidol 2001;12:35-40. |
|16.||Macfarlane S, Macfarlane GT, Cummings JH. Prebiotics in the gastrointestinal tract. Aliment Pharmacol Ther 2006;24:701-14. |
|17.||Emanuel V, Adrian V. The influence of prebiotics on bacteriocin synthesis using the strain Lactobacillus paracasei CMGB16. Afr J Microbiol Res 2010;4:534-7. |
|18.||Cani PD, Neyrinck AM, Maton N, Delzenne NM. Oligofructose Promotes Satiety in Rats Fed a High-Fat Diet: Involvement of Glucagon-Like Peptide-1. Obesity Res 2005;13:1000-7. |
|19.||Giaccoa R, Clementea G, Luongoa D, Lasorellaa G, Fiumea I, Brounsb F, et al. Effects of short-chain fructo-oligosaccharides on glucose and lipid metabolism in mild hypercholesterolaemic individuals. Clin Nutr 2003;23:331-40. |