Prebiotics.com

Is dedicated to educating health professionals and consumers about prebiotics and their role in human health.

Types of Prebiotics   Health Impacts

What are Prebiotics

Prebiotics are non-digestible ingredients, typically low molecular weight oligosaccharides, that persist into the colon where they feed beneficial bacteria.

Official Definition

According to the International Scientific Association for Probiotics and Prebiotics, Prebiotics are defined as "a selectively fermented ingredient that results in specific changes in the composition and/or activity of the gastrointestinal microbiota, thus conferring benefit(s) upon host health." (Gibson et al. 2010. Food Science and Technology Bulletin: Functional Foods 7 (1) 1-19.)

A key term in this definition is "fermented", which means that the prebiotic must be used by microbes to promote their growth and/or to produce metabolites. Compounds that change the composition of the microbiota without promoting the grown of certain microbes would not be considered prebiotics. This would include compounds with antimicrobial properties.

Another key term in this definition is "selectively". This means that a prebiotic must support the growth of only some microbes, rather than a compound like glucose that would feed virtually all microbes within the digestive tract. And, by stipulating that prebiotics must confer benefits upon host health, which means that the microbes fed by prebiotics must be considered beneficial, such as Lactobacilli or Bifidobacteria.

This website features the most up-to-date scientifically reviewed information about:

  • Prebiotic science
  • Prebiotic products
  • Role of prebiotics & probiotics in health

Information provided on this site will include per-reviewed publications, reports and analyses from scientific and regulatory bodies such as the ISAPP, the Institute of Medicine (IOM), the International Life Sciences Institute (ILSI), and the FAO.

Food Sources of Prebiotics

Prebiotics such as FOS and inulin are naturally present in some foods, particularly wheat and grain products, Jerusalem artichokes, garlic, onions, and bananas. However, you can't get enough prebiotics from food (unless you eat 15 green bananas or nearly a pound of asparagus every day).

Types of Prebiotics

To learn more about different types of prebiotics, select a prebiotic listed below for more information.

Short chain fructo-oligosaccharides (FOS) are produced enzymatically by adding fructose subunits onto sucrose. Short chain FOS thus includes a glucose unit at the end of its structure.

Oligofructose, another type of FOS, is also mainly made up of fructose subunits, and tends to have a greater degree of polymerization. It is often produced from inulin using a final hydrolysis step. Oligofructose derived from chicory may contain fructose chains alone, or fructose chains with glucose units at either end.
Isomalto-oligosaccharides (IMOS) are produced by enzyme-catalyzed hydrolysis of starch, followed by removal of glucose using yeast. The alpha-1,4 glycoside linkages in the maltooligosaccharide intermediate are then converted enzymatically into alpha-1,6 linkages using a transglycosidase enzyme. The change from alpha-1,4 to alpha-1,6 linkages makes the molecule less susceptible to digestion.
Resistant starch is starch that is not readily hydrolyzed by amylase or pullulanase. It may take one of four forms. The first form, RS1, is the starch within milled grains and seeds that is physically inaccessible to enzymes. RS2 is a tightly packed, compact polymer that limits access to water and enzymes.

RS3 is the most resistant form, essentially retrograded amylose produced after gelatinized starch has been cooled. RS4 is a chemically crosslinked or enzymatically modified form of starch. Crosslinking agents such as phosphates, acetate, or adipic acid are commonly used for RS4. Corn and rice are typical sources for these starches.
Galacto-oligosaccharides (GOS) are produced from the galactan fraction in plant fiber, or more commonly, produced enzymatically by a transglycosylation reaction using lactose as the substrate. The GOS produced enzymatically tends to have a low degree of polymerization, and includes unreacted lactose, galactose and glucose.
Inulin is often produced by direct extraction from inulin-rich plants such as chicory roots or Jerusalem artichokes. Inulin is also made up of fructose subunits, with 11 to 60 fructose subunits typical in most inulin products. Its larger structure means that it tends to be insoluble, unlike most shorter-chain oligosaccharide prebiotics.
There are other compounds that are considered "emerging prebiotics" - which means there is preliminary information about them from lab or animal trials, but they may not have undergone clinical trials to show health benefits. Also, some compounds are marketed as prebiotics, but do not meet the accepted scientific definition - be careful of these compounds - if something is claimed to be a prebiotic, but has not be recognized as such by regulatory agencies or scientific bodies, you may not see the types of benefits that have been shown with well-researched prebiotics like FOS, GOS, HMOS, Inulin and XOS.
Human Milk Oligosaccharides (HMOS) are found in breastmilk and selectively feed certain strains of bifidobacteria within the infant's developing digestive tract. These compounds have complex structures, and are unique to breastmilk.
Xylo-oligosaccharides are natural fiber components of plants and certain grains, fruits and vegetables, produced when their long chain parent compound (xylan) is broken down into smaller components during digestion.

Xylo-oligosaccharides are made up of multiple xylose units, linked together. The number of units may range from 2 to 50 or more. Because they are based upon xylose, a 5-carbon sugar, they are less susceptible to digestion than other oligosaccharides that are based upon 6-carbon sugars.

Health Impacts of Prebiotics

Typically, prebiotics help the beneficial bacteria within the gastrointestinal tract to grow. The most prominent benefit is to improve digestive health. Generally, people who consume more fiber and prebiotics have more Firmicutes, Bacteriodes, Actinobacteria, Prevotella and Xylanobacter in their digestive tract. These genera are also adept at fermenting xylans.

Consuming prebiotics has many impacts on bacteria within the digestive tract. Typically, prebiotics stimulate the growth of lactobacilli and bifidobacteria, producing key metabolites, such as lactate and short chain fatty acids (SCFAs), that have direct and indirect health benefits. Notably, acetate, propionate and butyrate play a role in regulating cholesterol, lipids, and glucose in the body.

Collectively, these SCFAs also reduce the pH in the colon, which inhibits growth of certain pathogenic species that tend to grow at higher pH. The lower pH also promotes the absorption of key minerals such as calcium and magnesium, which are more soluble under lower pH conditions, and thus more readily absorbed. This could provide benefits for adolescents as bones are formed, and may help to prevent or manage osteoporosis.

Frequently Asked Questions


Prebiotics are different types of oligosaccharides - chains of sugar molecules. They can be made up of multiple units of, e.g., fructose, glucose, galactose, mannose, and xylose. Inulin, a prebiotic also known as oligofructose, is made up of multiple units of fructose.
Prebiotics can be taken daily. We feed ourselves daily, and should feed the good microbes every day too!
Probiotics are microbes - typically bifidobacteria and lactobacilli. Prebiotics are the food source that helps the good microbes to grow.
Yes, they have been part of our diet ever since humans consumed grains, and certain fruits and vegetables. Many have undergone review by the FDA, and are Generally Regarded As Safe (GRAS).
However, some people have certain health issues or may have intolerances to components in certain prebiotics, such as residual lactose in GOS. It is always recommended to check with your doctor, dietitian, or health professional before taking any supplement.
Yes, prebiotics can boost the effectiveness of probiotics.
The International Life Science Institute and ISAPP suggest a daily intake of 5 - 20 grams per day, depending upon the type of prebiotic and desired effect. Prebiotics such as FOS and inulin require doses in the range of 10 - 20 grams per day, while health benefits have been shown with XOS at doses from 1.5 to 4 grams per day. Most people will consume 1 - 2 grams of FOS/inulin as part of their normal food intake; to reach an effective dose, a supplement or food/beverage fortified with prebiotics would be needed.

Research News

Check out some relevant research and developments in the field of prebiotics.

Westfall et al. from McGill University recently published a study discussing the link between gut microflora and the development of diabetes, Parkinson's disease and Alzheimer's disease. They suggest that enhancing or re-establishing the Lactobacillus spp. and Bifidobacterium spp. populations in the gut, along with corresponding changes in short chain fatty acids, can influence the development and management of these diseases.
Scientific American published an informative article looking at the role of fiber in our diets, and its impact upon the gut microbial community. The article summarizes key observations from several research groups, and discusses the importance of feeding the good bacteria that we already have within our gastrointestinal tract.
Saville et al. (AGRO Food Industry Hi Tech, vol 27(5), 5, 2016) reviewed different sources and types of prebiotics, structural differences that affect their use by different microbes, and doses required for health benefits.
Krumbeck et al. from the University of Nebraska and the University of Alberta discuss the merits of parallel administration of prebiotics and probiotics, or so-called "synbiotics". They isolated a specific strain of Bifidobacteria (Bifidobacterium adolescentis strain IVS-1) that was enriched during administration of galactooligosaccharides. They subsequently delivered IVS-1 and the prebiotic to rats, demonstrating that the synbiotic formulation led to superior growth in the GI tract compared to delivering the probiotic or prebiotic alone. Their work also identifies a model for tailored development of synbiotics, matching particular bacterial strains with specific prebiotics to enhance health benefits.
See: Appl. Envir. Microbiol. 81(7), 2455 - 2465 (2015).
Collins and Reid (Nutrients, vol 8(9), p523, 2016) present a comprehensive review of health effects/impacts of various prebiotics, and their mechanism of action. The review summarizes clinical trial findings for prebiotics when used to assess immune system impacts, mineral absorption, and serum lipids.
The International Scientific Association for Probiotics and Prebiotics (ISAPP) is "an association of academic and industrial scientists involved in research on fundamental and applied aspects of probiotics and prebiotics. The scientists participating in ISAPP have a common interest in generating high quality scientific information for the probiotic and prebiotic fields and providing guidance for collaborative and multidisciplinary research."
Brownawell et al. (J, Nutrition, vol 142(5), 962, 2012) present a summary of findings related to the role of prebiotics in management of GI disorders, promotion of satiety and weight loss, and enhancing the uptake and bioavailability of minerals. This comprehensive review also discusses the regulatory status in various jurisdictions, including the U.S., Canada, Europe, Japan, Korea, and South America. The document concludes with a summary of research needs and future developments for prebiotics.

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