Prebiotics are compounds in food that induce the growth or activity of beneficial microorganisms such as bacteria and fungi. The most common example is in the gastrointestinal tract, where prebiotics can alter the composition of organisms in the gut microbiome.
Dietary prebiotics are typically nondigestible fiber compounds that pass undigested through the upper part of the gastrointestinal tract and stimulate the growth 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 a conceptual intermediary 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 for marketing purposes.
The definition of prebiotics and the food ingredients that can fall under this classification, has evolved since its first definition in 1995. In its earliest definition, the term prebiotics was used to refer to non-digestible food ingredients that were beneficial to the host through their selective stimulation of specific bacteria within the colon. As a result of research suggesting that prebiotics could impact microorganisms outside of the colon, in 2016 the International Scientific Association for Probiotics and Prebiotics (ISAPP) produced the following definition of prebiotics: a substrate that is selectively used by a host microorganism to produce a health benefit.
- non-digestible and resistant to breakdown by stomach acid and enzymes in the human gastrointestinal tract
- selectively fermented by intestinal microorganisms
- selectively targeting and stimulating the growth and activity of beneficial bacteria
Thus, consumption of prebiotics may facilitate the health of the host. Based on the previous classifications, plant-derived carbohydrate compounds called oligosaccharides are the main source of prebiotics that have been identified. Specifically, fructans and galactans are two oligosaccharide sources which have been found to stimulate the activity and growth of beneficial bacterial colonies in the gut. Fructans are a category of carbohydrate consisting of fructooligosaccharides (FOS) and inulins, while galactans consist of galactooligosaccharides (GOS). Other dietary fibers also fit the definition of prebiotics, such as resistant starch, pectin, beta-glucans, and xylooligosaccharides.
The European Food Safety Authority (EFSA), the regulatory agency for product labeling, differentiates between "prebiotic" and "dietary fiber", stating that "a cause and effect relationship has not been established between the consumption of the food constituents which are the subject of the health claims and a beneficial physiological effect related to increasing numbers of gastrointestinal microbiota". Consequently, under EFSA rules individual ingredients cannot be labeled as prebiotics, but only as dietary fiber and with no implication of health benefits.
Most prebiotic research has focused on the effects that prebiotics confer on Bifidobacteria and Lactobacillus. These bacteria have been highlighted as key probiotics and beneficial gut bacteria as they may have several beneficial effects on the host in terms of improving digestion (including but not limited to enhancing mineral absorption) and the effectiveness and intrinsic strength of the immune system. Both Bifidobacteria and Lactobacillus have been shown to have differing prebiotic specificity and to selectively ferment prebiotic fiber based on the enzymes characteristic of the bacterial population. Thus, Lactobacilli prefers inulin and fructooligosaccharides, while Bifidobacteria displays specificity for inulin, fructooligosaccharides, xylooligosaccharides and galactooligosaccharides. A product that stimulates bifidobacteria is described as a bifidogenic factor, a concept that overlaps, but is not identical with, being prebiotic. Studies have also shown that prebiotics, besides stimulating the growth of beneficial gut bacteria, can also inhibit the growth of detrimental and potentially pathogenic microbes in the gut, such as clostridia.
Mechanism of action
Fermentation is the main mechanism of action by which prebiotics are used by beneficial bacteria in the colon. Both Bifidobacteria and Lactobacillus are bacterial populations which use saccharolytic metabolism to break down substrates. The bifidobacterial genome contains many genes that encode for carbohydrate-modifying enzymes as well as genes that encode for carbohydrate uptake proteins. The presence of these genes indicates that Bifidobacteria contain specific metabolic pathways specialized for the fermentation and metabolism of plant-derived oligosaccharides, or prebiotics. These pathways in Bifidobacteria ultimately produce short chain fatty acids, which have diverse physiological roles in body functions.
Prebiotic sources must be proven to confer a benefit to the host in order to be classified as a prebiotic. Fermentable carbohydrates derived from fructans and xylans are the most well documented example of prebiotics.
An endogenous source of prebiotics in humans is human breast milk, which contains oligosaccharides structurally similar to GOS, referred to as human milk oligosaccharides (HMOs). These HMOs were found to increase the Bifidobacteria bacterial population in breastfed infants, and to strengthen the infant immune system. Furthermore, HMOs play a role in the establishment of a healthy intestinal microbiota composition of newborns.
Indigestible carbohydrate compounds classified as prebiotics are a type of fermentable fiber, and thus can be classified as dietary fiber. However, not all dietary fiber can be classified as a prebiotic source. In addition to the food sources highlighted in the following table, raw oats, unrefined barley, yacón, and whole grain breakfast cereals are also classified as prebiotic fiber sources. The predominant type of prebiotic fiber may vary according to the food. For instance, oats and barley have high amounts of beta-glucans, fruit and berries contain pectins, seeds contain gums, onions and Jerusalem artichokes are rich in inulin and oligofructose, and bananas and legumes contain resistant starch.
|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 fructans|
|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)|
Preliminary research has demonstrated potential effects on calcium and other mineral absorption, immune system effectiveness, bowel acidity, reduction of colorectal cancer risk, inflammatory bowel disease (Crohn's disease or ulcerative colitis), hypertension and defecation frequency. Prebiotics may be effective in decreasing the number of infectious episodes needing antibiotics and the total number of infections in children aged 0–24 months.
No good evidence shows that prebiotics are effective in preventing or treating allergies.
While research demonstrates that prebiotics lead to increased production of short-chain fatty acids (SCFA), more research is required to establish a direct causal connection. Prebiotics may be beneficial to inflammatory bowel disease or Crohn's disease through production of SCFA as nourishment for colonic walls, and mitigation of ulcerative colitis symptoms.
The sudden addition of substantial quantities of prebiotics to the diet may result in an increase in fermentation, leading to increased gas production, bloating or bowel movement. Production of SCFA and fermentation quality are reduced during long-term diets of low fiber intake. Until bacterial flora are gradually established to rehabilitate or restore intestinal bacteria, nutrient absorption may be impaired and colonic transit time temporarily increased with a rapid addition of higher prebiotic intake.
- Prebiotic scores
- Mannan oligosaccharides (MOS)
- Resistant starch
- Hutkins RW; Krumbeck JA; Bindels LB; Cani PD; Fahey G Jr.; Goh YJ; Hamaker B; Martens EC; Mills DA; Rastal RA; Vaughan E; Sanders ME (2016). "Prebiotics: why definitions matter". Curr Opin Biotechnol. 37: 1–7. doi:10.1016/j.copbio.2015.09.001. PMC 4744122. PMID 26431716.
- Gibson GR, Roberfroid MB (June 1995). "Dietary modulation of the human colonic microbiota: introducing the concept of prebiotics". J. Nutr. 125 (6): 1401–1412. doi:10.1093/jn/125.6.1401. PMID 7782892.
- Gibson GR, Hutkins R, Sanders ME, Prescott SL, Reimer RA, Salminen SJ, et al. (August 2017). "Expert consensus document: The International Scientific Association for Probiotics and Prebiotics (ISAPP) consensus statement on the definition and scope of prebiotics" (PDF). Nature Reviews. Gastroenterology & Hepatology. 14 (8): 491–502. doi:10.1038/nrgastro.2017.75. PMID 28611480.
- Slavin J (April 2013). "Fiber and prebiotics: mechanisms and health benefits". Nutrients. 5 (4): 1417–35. doi:10.3390/nu5041417. PMC 3705355. PMID 23609775.
- Lamsal BP (August 2012). "Production, health aspects and potential food uses of dairy prebiotic galactooligosaccharides". Journal of the Science of Food and Agriculture. 92 (10): 2020–8. doi:10.1002/jsfa.5712. PMID 22538800.
- CK Rajendran SR, Okolie CL, Udenigwe CC, Mason B (1 October 2017). "Structural features underlying prebiotic activity of conventional and potential prebiotic oligosaccharides in food and health". Journal of Food Biochemistry. 41 (5): e12389. doi:10.1111/jfbc.12389. ISSN 1745-4514.
- Pokusaeva K, Fitzgerald GF, van Sinderen D (August 2011). "Carbohydrate metabolism in Bifidobacteria". Genes & Nutrition. 6 (3): 285–306. doi:10.1007/s12263-010-0206-6. PMC 3145055. PMID 21484167.
- Zaman SA, Sarbini SR (7 July 2015). "The potential of resistant starch as a prebiotic" (PDF). Critical Reviews in Biotechnology. 36 (3): 578–84. doi:10.3109/07388551.2014.993590. PMID 25582732.
- Gómez B, Gullón B, Remoroza C, Schols HA, Parajó JC, Alonso JL (October 2014). "Purification, characterization, and prebiotic properties of pectic oligosaccharides from orange peel wastes". Journal of Agricultural and Food Chemistry. 62 (40): 9769–82. doi:10.1021/jf503475b. PMID 25207862.
- Arena MP, Caggianiello G, Fiocco D, Russo P, Torelli M, Spano G, Capozzi V (February 2014). "Barley β-glucans-containing food enhances probiotic performances of beneficial bacteria". International Journal of Molecular Sciences. 15 (2): 3025–39. doi:10.3390/ijms15023025. PMC 3958897. PMID 24562330.
- Linares-Pasten JA, Aronsson A, Karlsson EN (2017). "Structural Considerations on the Use of Endo-Xylanases for the Production of prebiotic Xylooligosaccharides from Biomass". Current Protein & Peptide Science. 19 (1): 48–67. doi:10.2174/1389203717666160923155209. PMC 5738707. PMID 27670134.
- Delcour JA, Aman P, Courtin CM, Hamaker BR, Verbeke K (January 2016). "Prebiotics, Fermentable Dietary Fiber, and Health Claims". Advances in Nutrition. 7 (1): 1–4. doi:10.3945/an.115.010546. PMC 4717894. PMID 26773010.
- Pandey KR, Naik SR, Vakil BV (December 2015). "Probiotics, prebiotics and synbiotics- a review". Journal of Food Science and Technology. 52 (12): 7577–87. doi:10.1007/s13197-015-1921-1. PMC 4648921. PMID 26604335.
- Coxam V (November 2007). "Current data with inulin-type fructans and calcium, targeting bone health in adults". The Journal of Nutrition. 137 (11 Suppl): 2527S–2533S. doi:10.1093/jn/137.11.2527S. PMID 17951497.
- Seifert S, Watzl B (November 2007). "Inulin and oligofructose: review of experimental data on immune modulation". The Journal of Nutrition. 137 (11 Suppl): 2563S–2567S. doi:10.1093/jn/137.11.2563S. PMID 17951503.
- Wilson B, Whelan K (March 2017). "Prebiotic inulin-type fructans and galacto-oligosaccharides: definition, specificity, function, and application in gastrointestinal disorders". Journal of Gastroenterology and Hepatology. 32 Suppl 1: 64–68. doi:10.1111/jgh.13700. PMID 28244671.
- "Prebiotics". Food-Info.net. Wageningen University.
- Byrne CS, Chambers ES, Morrison DJ, Frost G (September 2015). "The role of short chain fatty acids in appetite regulation and energy homeostasis". International Journal of Obesity. 39 (9): 1331–8. doi:10.1038/ijo.2015.84. PMC 4564526. PMID 25971927.
- Enam F, Mansell TJ (October 2019). "Prebiotics: tools to manipulate the gut microbiome and metabolome". Journal of Industrial Microbiology & Biotechnology. 46 (9–10): 1445–1459. doi:10.1007/s10295-019-02203-4. PMID 31201649.
- "Definitions of fiber". Micronutrient Information Center, Linus Pauling Institute, Oregon State University, Corvallis, OR. 1 April 2012. Retrieved 27 February 2019.
- 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. doi:10.1093/jn/129.7.1407S. PMID 10395608.
- Scholz-Ahrens KE, Schrezenmeir J (November 2007). "Inulin and oligofructose and mineral metabolism: the evidence from animal trials". J. Nutr. 137 (11 Suppl): 2513S–2523S. doi:10.1093/jn/137.11.2513S. PMID 17951495.
- Lomax AR, Calder PC (March 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.
- Lohner S, Küllenberg D, Antes G, Decsi T, Meerpohl JJ (2014). "Prebiotics in healthy infants and children for prevention of acute infectious diseases: a systematic review and meta-analysis". Nutr Rev. 72 (8): 523–31. doi:10.1111/nure.12117. PMID 24903007.
- Geier MS, Butler RN, Howarth GS (October 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 (August 2007). "Evidence for the use of probiotics and prebiotics in inflammatory bowel disease: a review of clinical trials". Proceedings of the Nutrition Society. 66 (3): 307–315. doi:10.1017/S0029665107005563. PMID 17637082.
- Yeo SK, Ooi LG, Lim TJ, Liong MT (2009). "Antihypertensive properties of plant-based prebiotics". Int J Mol Sci. 10 (8): 3517–30. doi:10.3390/ijms10083517. PMC 2812835. PMID 20111692.
- Roberfroid M, et al. (2010). "Prebiotic effects: metabolic and health benefits". Br J Nutr. 104 (Suppl 2): S1–63. doi:10.1017/S0007114510003363. PMID 20920376.
- Cuello-Garcia C, Fiocchi A, Pawankar R, Yepes-Nuñez JJ, Morgano GP, Zhang Y, Agarwal A, Gandhi S, Terracciano L, Schünemann HJ, Brozek JL (November 2017). "Prebiotics for the prevention of allergies: A systematic review and meta-analysis of randomized controlled trials". Clin. Exp. Allergy (Systematic review). 47 (11): 1468–1477. doi:10.1111/cea.13042. PMID 29035013.
- Macfarlane S, Macfarlane GT, Cummings JH (September 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.
- Guarner F (2005). "Inulin and oligofructose: impact on intestinal diseases and disorders". Br J Nutr. 93 (Suppl 1): S61–5. doi:10.1079/BJN20041345. PMID 15877897.
- Marteau P, Seksik P (2004). "Tolerance of probiotics and prebiotics". J Clin Gastroenterol. 38 (Suppl 6): S67–9. doi:10.1097/01.mcg.0000128929.37156.a7. PMID 15220662.
- El Oufir L, Flourié B, Bruley des Varannes S, Barry JL, Cloarec D, Bornet F, Galmiche JP (June 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". Proceedings of the Nutrition Society. 55 (3): 899–912. doi:10.1079/PNS19960087. PMID 9004332.
- 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. hdl:1874/11465. PMID 17134393.
- Frank W. Jackson, PREbiotics, Not Probiotics. December 2, 2013, Jacksong GI Medical. ISBN 978-0991102709.
|Wikimedia Commons has media related to Prebiotics.|