Prebiotic (nutrition)
Encyclopedia
Prebiotics are non-digestible food ingredients that stimulate the growth and/or activity of bacteria in the digestive system in ways claimed to be beneficial to health. They were first identified and named by Marcel Roberfroid in 1995. As a functional food
component, prebiotics, like probiotics, are conceptually intermediate between food
s and drug
s. Depending on the jurisdiction, they typically receive an intermediate level of regulatory scrutiny, in particular of the health claims
made concerning them.
Typically, prebiotics are carbohydrates (such as oligosaccharide
s), but the definition may include non-carbohydrates. The most prevalent forms of prebiotics are nutritionally classed as soluble fiber. To some extent, many forms of dietary fiber
exhibit some level of prebiotic effect.
Roberfroid offered a refined definition in the 2007 Journal of Nutrition stating:
Additionally, in his 2007 revisit of Prebiotics, Roberfroid stated that only two particular fructooligosaccharide
s fully meet this definition: oligofructose and inulin
. Other authorities also classify galactooligosaccharides
(GOS) as prebiotics. 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, 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 importance of the bifidobacteria and the lactic acid bacteria (AKA lactobacillus or LABs) 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. 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.
sources (such as Jerusalem artichoke
, jicama
, and chicory
root), raw oat
s, 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.
It is becoming more common to properly distinguish between prebiotic substances and the food that contains them. References to almonds, honey and other foods (most commonly in promotional materials from growers of those foods) as "a prebiotic" are not accurate. No plant or food is a prebiotic: Wheat, honey and many other foods contain prebiotics to a greater or lesser extent, ranging from fairly large portions (chicory root, Jerusalem artichoke
) to only trace quantities (thousands of other plant-based foods). Referring to a food as "a prebiotic" is no more accurate than calling a food "a vitamin."
Top 10 Foods Containing Prebiotics
While there is no broad consensus on an ideal daily serving of prebiotics, recommendations typically range from 4-8g for general digestive health support, to 15g or more for those with active digestive disorders. Given an average 6g serving, below are the amounts of prebiotic foods required to achieve a daily serving of prebiotic fiber:
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 1.3 pounds of bananas daily is likely to provide an excess of calories & 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 fructooligosaccharide
s (FOS), xylooligosaccharides (XOS), polydextrose
and galactooligosaccharides
(GOS). Some monosaccharides such as tagatose
are also used sometimes as prebiotics.
In petfood also 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.
and bacteroides
species) are widely recognized to be beneficial.
While research does clearly demonstrate that prebiotics lead to increased production of these SCFA's, more research is required to establish a direct causal connection. 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 SCFAs create.
The immediate addition of substantial quantities of prebiotics to the diet may result in a temporary increase in gas, bloating or bowel movement. It has been argued 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.
Functional food
Functional food is a food where a new ingredient has been added to a food and the new product has a new function ....
component, prebiotics, like probiotics, are conceptually intermediate between food
Food
Food is any substance consumed to provide nutritional support for the body. It is usually of plant or animal origin, and contains essential nutrients, such as carbohydrates, fats, proteins, vitamins, or minerals...
s and drug
Drug
A drug, broadly speaking, is any substance that, when absorbed into the body of a living organism, alters normal bodily function. There is no single, precise definition, as there are different meanings in drug control law, government regulations, medicine, and colloquial usage.In pharmacology, a...
s. Depending on the jurisdiction, they typically receive an intermediate level of regulatory scrutiny, in particular of the health claims
Health claims on food labels
Health claims on food labels are claims by manufacturers of food products that their food will reduce the risk of developing a disease or condition...
made concerning them.
Typically, prebiotics are carbohydrates (such as oligosaccharide
Oligosaccharide
An oligosaccharide is a saccharide polymer containing a small number of component sugars, also known as simple sugars...
s), but the definition may include non-carbohydrates. The most prevalent forms of prebiotics are nutritionally classed as soluble fiber. To some extent, many forms of dietary fiber
Dietary fiber
Dietary fiber, dietary fibre, or sometimes roughage is the indigestible portion of plant foods having two main components:* soluble fiber that is readily fermented in the colon into gases and physiologically active byproducts, and* insoluble fiber that is metabolically inert, absorbing water as it...
exhibit some level of prebiotic effect.
Roberfroid offered a refined definition in the 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 fructooligosaccharide
Fructooligosaccharide
Fructooligosaccharides also sometimes called oligofructose or oligofructan, are oligosaccharide fructans, used as an alternative sweetener. FOS exhibits sweetness levels between 30 and 50 percent of sugar in commercially-prepared syrups...
s fully meet this definition: oligofructose and inulin
Inulin
Inulins are a group of naturally occurring polysaccharides produced by many types of plants. They belong to a class of fibers known as fructans. Inulin is used by some plants as a means of storing energy and is typically found in roots or rhizomes...
. Other authorities also classify galactooligosaccharides
Galactooligosaccharides
Galacto-oligosaccharides , also known as oligogalactosyllactose, oligogalactose, oligolactose or transgalactooligosaccharides , belong, because of their indigestible nature, to the group of prebiotics. Prebiotics are defined as non-digestible food ingredients that beneficially affect the host by...
(GOS) as prebiotics. 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, are typically fermented more quickly in the right-side
Ascending colon
The ascending colon is smaller in caliber than the cecum.It passes upward, from its commencement at the cecum, opposite the colic valve, to the under surface of the right lobe of the liver, on the right of the gall-bladder, where it is lodged in a shallow depression, the colic impression; here it...
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
Descending colon
The descending colon of humans passes downward through the left hypochondrium and lumbar regions, along the lateral border of the left kidney....
. 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.
Function
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 bacteriaLactic acid bacteria
The lactic acid bacteria comprise a clade of Gram-positive, low-GC, acid-tolerant, generally non-sporulating, non-respiring rod or cocci that are associated by their common metabolic and physiological characteristics. These bacteria, usually found in decomposing plants and lactic products, produce...
. The importance of the bifidobacteria and the lactic acid bacteria (AKA lactobacillus or LABs) 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. A product that stimulates bifidobacteria is considered a bifidogenic factor. Some prebiotics may thus also act as a bifidogenic factor
Bifidus Factor
A Bifidus factor is a compound that specifically enhances the growth of bifidobacteria in either a product or in the intestines of humans and/or animals. Several products have been marketed as bifidogenic factors, such as several prebiotics and methyl-N-acetyl D-glucosamine in human milk . The...
and vice versa, but the two concepts are not identical.
Sources
Traditional dietary sources of prebiotics include soybeans, inulinInulin
Inulins are a group of naturally occurring polysaccharides produced by many types of plants. They belong to a class of fibers known as fructans. Inulin is used by some plants as a means of storing energy and is typically found in roots or rhizomes...
sources (such as Jerusalem artichoke
Jerusalem artichoke
The Jerusalem artichoke , also called the sunroot, sunchoke, earth apple or topinambour, is a species of sunflower native to eastern North America, and found from Eastern Canada and Maine west to North Dakota, and south to northern Florida and Texas...
, jicama
Jícama
Pachyrhizus erosus, commonly known as Jícama , Yam, and Mexican Turnip, is the name of a native Mexican vine, although the name most commonly refers to the plant's edible tuberous root. Jícama is one species in the genus Pachyrhizus. Plants in this genus are commonly referred to as yam bean,...
, and chicory
Chicory
Common chicory, Cichorium intybus, is a somewhat woody, perennial herbaceous plant usually with bright blue flowers, rarely white or pink. Various varieties are cultivated for salad leaves, chicons , or for roots , which are baked, ground, and used as a coffee substitute and additive. It is also...
root), raw oat
Oat
The common oat is a species of cereal grain grown for its seed, which is known by the same name . While oats are suitable for human consumption as oatmeal and rolled oats, one of the most common uses is as livestock feed...
s, unrefined wheat
Wheat
Wheat is a cereal grain, originally from the Levant region of the Near East, but now cultivated worldwide. In 2007 world production of wheat was 607 million tons, making it the third most-produced cereal after maize and rice...
, unrefined barley
Barley
Barley is a major cereal grain, a member of the grass family. It serves as a major animal fodder, as a base malt for beer and certain distilled beverages, and as a component of various health foods...
and yacon
Yacón
The Yacón is a perennial plant traditionally grown in the Northern and Central Andes from Ecuador to Argentina for its crisp, sweet-tasting tuberous roots. The texture and flavour are very similar to jicama mainly differing in that yacon has some slightly sweet resinous and floral undertones to...
. Some of the oligosaccharides that naturally occur in breast milk
Breast milk
Breast milk, more specifically human milk, is the milk produced by the breasts of a human female for her infant offspring...
are believed to play an important role in the development of a healthy immune system
Immune system
An immune system is a system of biological structures and processes within an organism that protects against disease by identifying and killing pathogens and tumor cells. It detects a wide variety of agents, from viruses to parasitic worms, and needs to distinguish them from the organism's own...
in infants.
It is becoming more common to properly distinguish between prebiotic substances and the food that contains them. References to almonds, honey and other foods (most commonly in promotional materials from growers of those foods) as "a prebiotic" are not accurate. No plant or food is a prebiotic: Wheat, honey and many other foods contain prebiotics to a greater or lesser extent, ranging from fairly large portions (chicory root, Jerusalem artichoke
Jerusalem artichoke
The Jerusalem artichoke , also called the sunroot, sunchoke, earth apple or topinambour, is a species of sunflower native to eastern North America, and found from Eastern Canada and Maine west to North Dakota, and south to northern Florida and Texas...
) to only trace quantities (thousands of other plant-based foods). Referring to a food as "a prebiotic" is no more accurate than calling a food "a vitamin."
Top 10 Foods Containing Prebiotics
| Food | Prebiotic Fiber Content by Weight |
|---|---|
| Raw Chicory Chicory Common chicory, Cichorium intybus, is a somewhat woody, perennial herbaceous plant usually with bright blue flowers, rarely white or pink. Various varieties are cultivated for salad leaves, chicons , or for roots , which are baked, ground, and used as a coffee substitute and additive. It is also... Root |
64.6% |
| Raw Jerusalem Artichoke Jerusalem artichoke The Jerusalem artichoke , also called the sunroot, sunchoke, earth apple or topinambour, is a species of sunflower native to eastern North America, and found from Eastern Canada and Maine west to North Dakota, and south to northern Florida and Texas... |
31.5% |
| Raw Dandelion Greens | 24.3% |
| Raw Garlic Garlic Allium sativum, commonly known as garlic, is a species in the onion genus, Allium. Its close relatives include the onion, shallot, leek, chive, and rakkyo. Dating back over 6,000 years, garlic is native to central Asia, and has long been a staple in the Mediterranean region, as well as a frequent... |
17.5% |
| Raw Leek Leek The leek, Allium ampeloprasum var. porrum , also sometimes known as Allium porrum, is a vegetable which belongs, along with the onion and garlic, to family Amaryllidaceae, subfamily Allioideae... |
11.7% |
| Raw Onion Onion The onion , also known as the bulb onion, common onion and garden onion, is the most widely cultivated species of the genus Allium. The genus Allium also contains a number of other species variously referred to as onions and cultivated for food, such as the Japanese bunching onion The onion... |
8.6% |
| Cooked Onion Onion The onion , also known as the bulb onion, common onion and garden onion, is the most widely cultivated species of the genus Allium. The genus Allium also contains a number of other species variously referred to as onions and cultivated for food, such as the Japanese bunching onion The onion... |
5% |
| Raw Asparagus Asparagus Asparagus officinalis is a spring vegetable, a flowering perennialplant species in the genus Asparagus. It was once classified in the lily family, like its Allium cousins, onions and garlic, but the Liliaceae have been split and the onion-like plants are now in the family Amaryllidaceae and... |
5% |
| Raw Wheat bran | 5% |
| Whole Wheat flour Wheat flour Wheat flour is a powder made from the grinding of wheat used for human consumption. More wheat flour is produced than any other flour. Wheat varieties are called "clean," "white," or "brown" if they have high gluten content, and they are called "soft" or "weak" flour if gluten content is low... , Cooked |
4.8% |
| Raw Banana Banana Banana is the common name for herbaceous plants of the genus Musa and for the fruit they produce. Bananas come in a variety of sizes and colors when ripe, including yellow, purple, and red.... |
1% |
While there is no broad consensus on an ideal daily serving of prebiotics, recommendations typically range from 4-8g for general digestive health support, to 15g or more for those with active digestive disorders. Given an average 6g serving, below are the amounts of prebiotic foods required to achieve a daily serving of prebiotic fiber:
| Food | Amount of food to achieve 6g serving of prebiotics |
|---|---|
| Raw Chicory Root | 9.3g (about 1/3 oz) |
| Raw Jerusalem Artichoke | 19g (about 3/4 oz) |
| Raw Dandelion Greens | 24.7g (just under 1 oz) |
| Raw Garlic | 34.3 g (about 1.2 oz) |
| Raw Leek | 51.3g (about 1.8 oz) |
| Raw Onion | 69.8g (about 2.5 oz) |
| Cooked Onion | 120g (about 1/4 lb) |
| Raw Asparagus | 120g (about 1/4 lb) |
| Raw Wheat Bran | 120g (about 1/4 lb) |
| Whole Wheat Flour, Cooked | 125g (about 1/4 lb) |
| Raw Banana | 600g (about 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 1.3 pounds of bananas daily is likely to provide an excess of calories & 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 fructooligosaccharide
Fructooligosaccharide
Fructooligosaccharides also sometimes called oligofructose or oligofructan, are oligosaccharide fructans, used as an alternative sweetener. FOS exhibits sweetness levels between 30 and 50 percent of sugar in commercially-prepared syrups...
s (FOS), xylooligosaccharides (XOS), polydextrose
Polydextrose
Polydextrose is an indigestable synthetic polymer of glucose. It is a food ingredient classified as soluble fiber by the U.S. Food and Drug Administration , but not Health Canada. It is frequently used to increase the non-dietary fiber content of food, replace sugar, reduce calories and reduce fat...
and galactooligosaccharides
Galactooligosaccharides
Galacto-oligosaccharides , also known as oligogalactosyllactose, oligogalactose, oligolactose or transgalactooligosaccharides , belong, because of their indigestible nature, to the group of prebiotics. Prebiotics are defined as non-digestible food ingredients that beneficially affect the host by...
(GOS). Some monosaccharides such as tagatose
Tagatose
Tagatose is a functional sweetener. It is a naturally occurring monosaccharide, specifically a hexose. It is often found in dairy products, and is very similar in texture to sucrose and is 92% as sweet, but with only 38% of the calories....
are also used sometimes as prebiotics.
In petfood also 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.
Effects
Studies have demonstrated positive 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 (high blood pressure) and intestinal regularity. Recent human trials have reinforced the role of Prebiotics in preventing and possibly stopping early stage colon cancer. It has been argued 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 clostridiaClostridium
Clostridium is a genus of Gram-positive bacteria, belonging to the Firmicutes. They are obligate anaerobes capable of producing endospores. Individual cells are rod-shaped, which gives them their name, from the Greek kloster or spindle...
and bacteroides
Bacteroides
Bacteroides is a genus of Gram-negative, bacillus bacteria. Bacteroides species are non-endospore-forming, anaerobes, and may be either motile or non-motile, depending on the species. The DNA base composition is 40-48% GC. Unusual in bacterial organisms, Bacteroides membranes contain sphingolipids...
species) are widely recognized to be beneficial.
While research does clearly demonstrate that prebiotics lead to increased production of these SCFA's, more research is required to establish a direct causal connection. 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 SCFAs create.
The immediate addition of substantial quantities of prebiotics to the diet may result in a temporary increase in gas, bloating or bowel movement. It has been argued 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.
See also
- Prebiotic scoresPrebiotic scoresA prebiotic score is a term sometimes used to estimate the health effects of prebiotics in humans or animals. There is no definition of prebiotic scores. The idea is that prebiotics may have many different effects in the human gut, some of these may be quantified and combined to an overall score...
- ProbioticProbioticProbiotics are live microorganisms thought to be beneficial to the host organism. According to the currently adopted definition by FAO/WHO, probiotics are: "Live microorganisms which when administered in adequate amounts confer a health benefit on the host"...
- Mannan Oligosaccharides (MOS)