Nutritional chemicals that help growth of microorganisms
Not to be confused withProbiotics, microorganisms typically found in fermented foods.
Prebiotics are compounds in food that foster growth or activity of beneficialmicroorganisms such as bacteria and fungi.[1] The most common environment concerning their effects on human health is the gastrointestinal tract, where prebiotics can alter the composition of organisms in thegut microbiome.
Dietary prebiotics are typically nondigestiblefiber compounds that pass undigested through the upper part of thegastrointestinal tract and help growth or activity of advantageous bacteria in thecolon by acting assubstrates for them.[1] They were first identified and named by Marcel Roberfroid in 1995.[1][2] Depending on the jurisdiction, they may have regulatory scrutiny asfood additives for thehealth claims made for marketing purposes. Common prebiotics used in food manufacturing includebeta-glucan fromoats,resistant starch from grains and beans, andinulin fromchicory root.
The definition of prebiotics and the food ingredients that can fall under this classification, has evolved since its first definition in 1995.[3] 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 thecolon.[3][4] Further research has suggested that selective stimulation has not been scientifically demonstrated.[5] As a result of research suggesting that prebiotics could impact microorganisms outside of the colon, in 2016 theInternational Scientific Association for Probiotics and Prebiotics (ISAPP) produced the following definition of prebiotics: asubstrate that is selectively used by a host microorganism to produce a health benefit.[3] In 2021, The Global Prebiotic Association (GPA) defined a prebiotic as a product or ingredient that is utilized in the microbiota producing a health or performance benefit.[6]
Compounds that can be classified as prebiotics must also meet the following criteria:[3][4][6]
non-digestible and resistant to breakdown by stomach acid and enzymes in the humangastrointestinal tract
fermented by microorganisms on or in the body
stimulating growth and activity of beneficial bacteria
Thus, consumption of prebiotics may facilitate the health of the host.[7] Based on the previous classifications, plant-derived carbohydrate compounds calledoligosaccharides as well as resistant starch are the main source of prebiotics that have been identified.[8][4][9][10] Specifically,fructans andgalactans are two oligosaccharide sources which have been found to stimulate the activity and growth of beneficial bacterial colonies in the gut.[7][3] Fructans are a category of carbohydrate consisting offructooligosaccharides (FOS) andinulins, while galactans consist ofgalactooligosaccharides.[3] Resistant starch has been shown to shift the intestinal bacteria, as well as improve biomarkers for numerous health conditions.[11][12][13] Other dietary fibers also fit the definition of prebiotics, such aspectin,[14]beta-glucans,[15] andxylooligosaccharides.[16]
TheEuropean Food Safety Authority (EFSA), the regulatory agency for product labeling, differentiates between "prebiotic" and "dietary fiber", stating that "acause 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".[17] Consequently, under EFSA rules individual ingredients cannot be labeled as prebiotics, but only as dietary fiber and with no implication of health benefits.[17]
When the prebiotic concept was first introduced in 1995, the primary focus was on the effects that prebiotics confer onBifidobacteria andLactobacillus.[3][4][18] With improved mechanistic techniques in recent years, the current prebiotic targets have expanded to a wider range of microbes, includingRoseburia spp.,Eubacterium spp.,Akkermansia spp.,Christensenella spp.,Propionibacterium spp. andFaecalibacterium spp.[19] These bacteria have been highlighted as keyprobiotics 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)[20] and the effectiveness and intrinsic strength of the immune system.[21] BothBifidobacteria andLactobacillus have been shown to have differing prebiotic specificity and to selectively ferment prebiotic fiber based on the enzymes characteristic of the bacterial population.[22] Thus,Lactobacilli prefer inulin and fructooligosaccharides, whileBifidobacteria display specificity for inulin, fructooligosaccharides, xylooligosaccharides and galactooligosaccharides.[22] Studies have also shown that prebiotics, besides helping growth of beneficial gut bacteria, can also inhibit detrimental and potentially pathogenic microbes in the gut,[9][4] such asclostridia.[4]
Fermentation is the mainmechanism of action by which prebiotics are used by beneficial bacteria in the colon.[7][4] BothBifidobacteria andLactobacillus are bacterial populations which usesaccharolytic metabolism to break down substrates.[4] The bifidobacterialgenome contains manygenes that encode for carbohydrate-modifying enzymes as well as genes that encode for carbohydrate uptake proteins. The presence of these genes indicates thatBifidobacteria contain specific metabolic pathways specialized for the fermentation and metabolism of plant-derived oligosaccharides, or prebiotics. These pathways inBifidobacteria ultimately produceshort chain fatty acids,[4][7] which have diversephysiological roles in body functions.[23][3]
Prebiotic sources must be proven to confer a benefit to the host in order to be classified as a prebiotic.[3] Fermentablecarbohydrates derived fromfructans andxylans are one well documented example of prebiotics.[3] Resistant starch from starchy foods are also well documented prebiotics and have historically been the highest source of prebiotics in the diet, as 4–10% of starch in mixed diets has been shown to reach the large intestine.[24] One study reported that individuals consuming a traditional diet in Africa consumed 38 grams of resistant starch/day.[25]
An endogenous source of prebiotics in humans is humanbreast milk, which containsoligosaccharides structurally similar togalactooligosaccharides, referred to as human milk oligosaccharides.[26][9][22][3] Human milk oligosaccharides were found to increase theBifidobacteria bacterial population in breastfed infants, and to strengthen the infant immune system.[3][9] Furthermore, human milk oligosaccharides help establish a healthy intestinal microbiota composition in newborns.[3]
Indigestible carbohydrate compounds classified as prebiotics are a type offermentable fiber, and thus can be classified asdietary fiber.[4] However, not all dietary fiber can be classified as a prebiotic source.[4] In addition to the food sources highlighted in the following table, raw oats,[18]unrefined barley,[18]yacón,[18] and whole grainbreakfast cereals[4] 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 ofbeta-glucans, fruit and berries containpectins, seeds containgums, onions andJerusalem artichokes are rich ininulin andoligofructose, and bananas and legumes containresistant starch.[27]
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:
No good evidence shows that prebiotics are effective in preventing or treating allergies.[39]
While research demonstrates that prebiotics lead to increased production ofshort-chain fatty acids (SCFA),[40] more research is required to establish a direct causal connection. Prebiotics may be beneficial toinflammatory bowel disease or Crohn's disease through production of SCFA as nourishment for colonic walls, and mitigation of ulcerative colitis symptoms.[41]
The sudden addition of substantial quantities of prebiotics to the diet may result in an increase infermentation, leading to increased gas production,bloating orbowel movement.[42] Production of SCFA and fermentation quality are reduced during long-term diets of low fiber intake.[43] 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.[42][44]
^Gibson GR, Roberfroid MB (June 1995). "Dietary modulation of the human colonic microbiota: introducing the concept of prebiotics".J. Nutr.125 (6):1401–12.doi:10.1093/jn/125.6.1401.PMID7782892.
^abcdLamsal BP (August 2012). "Production, health aspects and potential food uses of dairy prebiotic galactooligosaccharides".Journal of the Science of Food and Agriculture.92 (10):2020–28.Bibcode:2012JSFA...92.2020L.doi:10.1002/jsfa.5712.PMID22538800.
^Bird, A.; Conlon, M.; Christophersen, C.; Topping, D. (2010). "Resistant starch, large bowel fermentation and a broader perspective of prebiotics and probiotics".Beneficial Microbes.1 (4):423–431.doi:10.3920/BM2010.0041.PMID21831780.
^Li, Cheng; Hu, Yiming (2022). "New definition of resistant starch types from the Gut Microbiota perspectives – a review".Critical Reviews in Food Science and Nutrition.63 (23):6412–6422.doi:10.1080/10408398.2022.2031101.PMID35075962.S2CID246277434.
^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.Bibcode:2014JAFC...62.9769G.doi:10.1021/jf503475b.PMID25207862.
^Cunningham, Marla; Azcarate-Peril, M. Andrea; Barnard, Alan; Benoit, Valerie; Grimaldi, Roberta; Guyonnet, Denis; Holscher, Hannah D.; Hunter, Kirsty; Manarung, Sarmauli; Obis, David; Petrova, Mariya I.; Steinert, Robert E.; Swanson, Kelly S.; van Sinderen, Douwe; Vulevic, Jelena; Gibson, Glenn R. (2021)."Shaping the future of probiotics and prebiotics".Trends in Microbiology.29 (8):667–685.doi:10.1016/j.tim.2021.01.003.PMID33551269.S2CID231864275.
^"Definitions of fiber". Micronutrient Information Center, Linus Pauling Institute, Oregon State University, Corvallis, OR. 1 April 2012. Retrieved27 February 2019.
^Geier MS, Butler RN, Howarth GS (October 2006). "Probiotics, prebiotics and synbiotics: a role in chemoprevention for colorectal cancer?".Cancer Biol. Ther.5 (10):1265–69.doi:10.4161/cbt.5.10.3296.PMID16969130.
^Koen Venema, Ana Paula do Carmo, ed. (2015).Probiotics and prebiotics: current research and future trends. Norfolk, UK: Caister Academic Press.ISBN978-1-910190-10-4.OCLC916950998.
^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):1468–77.doi:10.1111/cea.13042.PMID29035013.S2CID7314418.
^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):321–27.Bibcode:2004PBioJ...2..321W.doi:10.1111/j.1467-7652.2004.00074.x.hdl:1874/11465.PMID17134393.S2CID42177275.
