Prebiotics is a general term to refer to chemicals that induce the growth and/or activity of commensal microorganisms (e.g., bacteria and fungi) that contribute to the well-being of their host. The most common example is in the gastrointestinal tract, where prebiotics can alter the composition of organisms in the gut microbiome. However, in principle it is a more general term that can refer to other areas of the body as well. For example, certain hand moisturizers have been proposed to act as prebiotics to improve the activity and/or composition of the skin microbiota. 
In diet, prebiotics are typically non-digestible fiber compounds that pass undigested through the upper part of the gastrointestinal tract and stimulate the growth and/or activity of advantageous bacteria that colonize the large bowel by acting as substrate for them. They were first identified and named by Marcel Roberfroid in 1995. As a functional food component, prebiotics, like probiotics, are conceptually intermediate between foods and drugs. Depending on the jurisdiction, they typically receive an intermediate level of regulatory scrutiny, in particular of the health claims made concerning them.
Roberfroid offered a refined definition in the March 2007 Journal of Nutrition stating:
A prebiotic is a selectively fermented ingredient that allows specific changes, both in the composition and/or activity in the gastrointestinal microflora that confers benefits upon host well-being and health.
Additionally, in his 2007 revisit of prebiotics, Roberfroid stated that only two particular prebiotics then fully met this definition: trans-galactooligosaccharide and inulin. Resistant starch, Mannan Oligosaccharides (MOS) have been termed as prebiotics but would more correctly be termed immunosaccharides.
Researchers now also focus on the distinction between short-chain, long-chain, and full-spectrum prebiotics. "Short-chain" prebiotics, e.g. oligofructose, contain 2–8 links per saccharide molecule and are typically fermented more quickly in the right side of the colon providing nourishment to the bacteria in that area. Longer-chain prebiotics, e.g. inulin, contain 9-64 links per saccharide molecule, and tend to be fermented more slowly, nourishing bacteria predominantly in the left-side colon. Full-spectrum prebiotics provide the full range of molecular link-lengths from 2-64 links per molecule, and nourish bacteria throughout the colon, e.g. Oligofructose-Enriched Inulin (OEI). The majority of research done on prebiotics is based on full-spectrum prebiotics, typically using OEI as the research substance.
The prebiotic definition does not emphasize a specific bacterial group. Generally, however, it is assumed that a prebiotic should increase the number and/or activity of bifidobacteria and lactic acid bacteria. The importance of the bifidobacteria and the lactic acid bacteria (LABs) is that these groups of bacteria may 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. A product that stimulates bifidobacteria is considered a bifidogenic factor. Some prebiotics may thus also act as a bifidogenic factor and vice versa, but the two concepts are not identical.
Chicory root is considered the richest natural source. Other traditional dietary sources of prebiotics include beans, Jerusalem artichoke, jicama, raw oats, unrefined wheat, unrefined barley, and yacon. Some of the oligosaccharides that naturally occur in breast milk are believed to play an important role in the development of a healthy immune system in infants.
|Top 10 Foods Containing Prebiotics|
|Food||Prebiotic Fiber Content by Weight|
|Raw, Dry Chicory Root||64.6%|
|Raw, Dry Jerusalem Artichoke||31.5%|
|Raw, Dry Dandelion Greens||24.3%|
|Raw, Dry Garlic||17.5%|
|Raw, Dry Leek||11.7%|
|Raw, Dry Onion||8.6%|
|Raw Wheat bran||5%|
|Whole Wheat flour, Cooked||4.8%|
While there is no broad consensus on an ideal daily serving of prebiotics, recommendations typically range from 4 to 8 grams (0.14–0.28 oz) for general digestive health support, to 15 grams (0.53 oz) or more for those with active digestive disorders. Given an average 6 grams (0.21 oz) serving, below are the amounts of prebiotic foods required to achieve a daily serving of prebiotic fiber:
|Food||Amount of food to achieve 6 g serving of prebiotics|
|Raw Chicory Root||9.3 g (0.33 oz)|
|Raw Jerusalem Artichoke||19 g (0.67 oz)|
|Raw Dandelion Greens||24.7 g (0.87 oz)|
|Raw Garlic||34.3 g (1.21 oz)|
|Raw Leek||51.3 g (1.81 oz)|
|Raw Onion||69.8 g (2.46 oz)|
|Cooked Onion||120 g (4.2 oz)|
|Raw Asparagus||120 g (4.2 oz)|
|Raw Wheat Bran||120 g (4.2 oz)|
|Whole Wheat Flour, Cooked||125 g (4.4 oz)|
|Raw Banana||600 g (1.3 lb)|
Those wishing to ensure sufficient prebiotic intake should carefully consider the prebiotic content of their diet, as well as what caloric/nutritive load comes along with it: e.g., eating 600 grams (1.3 lb) of bananas daily is likely to provide an excess of calories and sugars/carbohydrates to the diet. Prebiotic fiber supplements with minimal caloric/fat/sugar load are also available.
Prebiotic oligosaccharides are increasingly added to foods for their health benefits. Some oligosaccharides that are used in this manner are fructooligosaccharides (FOS), xylooligosaccharides (XOS), polydextrose, and galactooligosaccharides (GOS). Moreover disaccharids like lactulose or some monosaccharides such as tagatose are also used sometimes as prebiotics.
Also in petfood, mannooligosaccharides are being used for prebiotic purposes.
Genetically engineering plants for the production of inulins has also become more prevalent, despite the still limited insight into the immunological mechanisms activated by such food supplementation.
Preliminary research has demonstrated potential effects on calcium and other mineral absorption, immune system effectiveness, bowel pH, reduction of colorectal cancer risk, inflammatory bowel disorders (Crohn's disease and ulcerative colitis) hypertension and intestinal regularity. Recent human trials have provided further evidence for the potential role of prebiotics in lowering risk of colon cancer. It has been argued[by whom?] that many of these health effects emanate from increased production of short-chain fatty acids (SCFA) by the stimulated beneficial bacteria. Thus food supplements specifically enhancing the growth of SCFA producing intestinal bacteria (such as clostridia and bacteroides species) are widely recognized to have such potential.
While research does clearly demonstrate that prebiotics lead to increased production of these SCFA, more research is required to establish a direct causal connection. It has been argued[by whom?] 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 SCFAs create.
The immediate addition of substantial quantities of prebiotics to the diet may result in an increase in gas, bloating or bowel movement. It has been argued[by whom?] that chronically low consumption of prebiotic-containing foods in the typical Western diet may exaggerate this effect.
Human colonic bacteria substrates are relatively stable. Production of SCFA and fermentation quality are reduced during long-term diets of low fiber intake. Until bacterial flora are gradually established to habilitate or restore intestinal tone, nutrient absorption will be impaired and colonic transit time temporarily increased with an immediate addition of higher prebiotic intake.
- Schloss, Patrick D. (1 October 2014). "Microbiology: An integrated view of the skin microbiome". Nature 514 (7520): 44–45. doi:10.1038/514044a.
- Gibson GR, Roberfroid MB (Jun 1995). "Dietary modulation of the human colonic microbiota: introducing the concept of prebiotics". J Nutr. 125 (6): 1401–1412. PMID 7782892.
- Roberfroid MB (March 2007). "Prebiotics: The Concept Revisited". J Nutr. 137 (3 Suppl 2): 830S–7S. PMID 17311983.
- Roberfroid M (2007). "Prebiotics: The Concept Revisited". J Nutr. 137 (3 Suppl 2): 830S–7S. PMID 17311983.
Presently there are only 2 food ingredients that fulfill these criteria, i.e., inulin and trans-galactooligosaccharides (TOS).
- Kleessen B, Hartmann L, Blaut M (2001). "Oligofructose and long-chain inulin: influence on the gut microbial ecology of rats associated with a human faecal flora". British Journal of Nutrition 86 (2): 291–300. doi:10.1079/BJN2001403. PMID 11502244.
- Femia AP, Luceri C, Dolara P, Giannini A, Biggeri A, Salvadori M, Clune Y, Collins KJ, Paglierani M, Caderni G (Nov 2002). "Antitumorigenic activity of the prebiotic inulin enriched with oligofructose in combination with the probiotics Lactobacillus rhamnosus and Bifidobacterium lactis on azoxymethane-induced colon carcinogenesis in rats". Carcinogenesis 23 (11): 1953–1960. doi:10.1093/carcin/23.11.1953. PMID 12419846.
- Hughes R, Rowland IR (Jan 2001). "Stimulation of apoptosis by two prebiotic chicory fructans in the rat colon". Carcinogenesis 22 (1): 43–47. doi:10.1093/carcin/22.1.43. PMID 11159739.
- Bouhnik Y, Vahedi K, Achour L, Attar A, Salfati J, Pochart P, Marteau P, Flourié B, Bornet F, Rambaud JC (Jan 1999). "Short-chain fructo-oligosaccharide administration dose-dependently increases fecal bifidobacteria in healthy humans". J Nutr. 129 (1): 113–116. PMID 9915885.
- Tahiri M, Tressol JC, Arnaud J, Bornet F, Bouteloup-Demange C, Feillet-Coudray C, Ducros V, Pépin D, Brouns F, Rayssiguier AM, Coudray C (Nov 2001). "Five-week intake of short-chain fructo-oligosaccharides increases intestinal absorption and status of magnesium in postmenopausal women". J Bone Miner Res. 16 (11): 2152–2160. doi:10.1359/jbmr.2001.16.11.2152. PMID 11697813.
- Coxam V (Nov 2007). "Current data with inulin-type fructans and calcium, targeting bone health in adults". J Nutr. 137 (11 Suppl): 2527S–2533S. PMID 17951497.
- Seifert S, Watzl B (Nov 2007). "Inulin and oligofructose: review of experimental data on immune modulation". J Nutr. 137 (11 Suppl): 2563S–2567S. PMID 17951503.
- "Prebiotics". Wageningen University.
- Jackson, Frank. "Breast Milk". Jackson GI Medical. Retrieved 23 April 2013.
- Moshfegh AJ, Friday JE, Goldman JP, Ahuja JK (July 1999). "Presence of inulin and oligofructose in the diets of Americans". Journal of Nutrition 129 (7 Suppl): 1407S–1411S. PMID 10395608.
- Ritsema T, Smeekens SC (2003). "Engineering fructan metabolism in plants". J Plant Physiol 160 (7): 811–820. doi:10.1078/0176-1617-01029. PMID 12940548.
- Weyens G, Ritsema T, Van Dun K, Meyer D, Lommel M, Lathouwers J, Rosquin I, Denys P, Tossens A, Nijs M, Turk S, Gerrits N, Bink S, Walraven B, Lefèbvre M, Smeekens S (2004). "Production of tailor-made fructans in sugar beet by expression of onion fructosyltransferase genes". Plant Biotechnol J 2 (4): 321–327. doi:10.1111/j.1467-7652.2004.00074.x. PMID 17134393.
- Peppelenbosch MP, Ferreira CV (2009). "Immunology of pre- and probiotic supplementation". Br J Nutr. 101 (1): 2–4. doi:10.1017/S0007114508020746. PMID 18577301.
- Scholz-Ahrens KE, Schrezenmeir J (Nov 2007). "Inulin and oligofructose and mineral metabolism: the evidence from animal trials". J Nutr. 137 (11 Suppl): 2513S–2523S. PMID 17951495.
- Lomax AR, Calder PC (Mar 2009). "Prebiotics, immune function, infection and inflammation: a review of the evidence". Br J Nutr. 101 (5): 633–658. doi:10.1017/S0007114508055608. PMID 18814803.
- Geier MS, Butler RN, Howarth GS (Oct 2006). "Probiotics, prebiotics and synbiotics: a role in chemoprevention for colorectal cancer?". Cancer Biol Ther. 5 (10): 1265–1269. doi:10.4161/cbt.5.10.3296. PMID 16969130.
- Hedin C, Whelan K, Lindsay JO (Aug 2007). "Evidence for the use of probiotics and prebiotics in inflammatory bowel disease: a review of clinical trials". Proc Nutr Soc. 66 (3): 307–315. doi:10.1017/S0029665107005563. PMID 17637082.
- "Antihypertensive Properties of Plant-Based Prebiotics". Siok-Koon Yeo, Lay-Gaik Ooi, Ting-Jin Lim, and Min-Tze Liong. School of Industrial Technology, Universiti Sains Malaysia, 11800 Penang, Malaysia.
- Munjal U, Glei M, Pool-Zobel BL, Scharlau D (Sep 2009). "Fermentation products of inulin-type fructans reduce proliferation and induce apoptosis in human colon tumour cells of different stages of carcinogenesis". Br J Nutr. 102 (5): 663–671. doi:10.1017/S0007114509274770. PMID 19250571.
- Macfarlane S, Macfarlane GT, Cummings JH (Sep 2006). "Review article: prebiotics in the gastrointestinal tract". Aliment Pharmacol Ther. 24 (5): 701–714. doi:10.1111/j.1365-2036.2006.03042.x. PMID 16918875.
- El Oufir L, Flourié B, Bruley des Varannes S, Barry JL, Cloarec D, Bornet F, Galmiche JP (Jun 1996). "Relations between transit time, fermentation products, and hydrogen consuming flora in healthy humans". Gut. 38 (6): 870–877. doi:10.1136/gut.38.6.870. PMC 1383195. PMID 8984026.
- Givson GR, Willems A, Reading S, Collins MD (1996). "Fermentation of non-digestible oligosaccharides by human colonic bacteria". Symposium 2. Proceedings of the Nutrition Society, 55:899–912.
- Frank W. Jackson, "PREbiotics, not Probiotics". December 2, 2013, Jacksong GI Medical. ISBN 978-0991102709.
- Food-Info.net on prebiotics and bifidogenic factors
- International Scientific Association for Probiotics and Prebiotics
- Prebiotic Potential Of Almonds, Sciencedaily.com
- Prebiotics -- The Key To Fewer Food Poisoning Stomach Upsets -- And Healthy Farm Animals, Sciencedaily.com
- The facts about prebiotics, Dailymail.co.uk