Prebiotic (nutrition)
Prebiotics are compounds in food that foster growth or activity of beneficial
Dietary prebiotics are typically nondigestible
Definition
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 the colon.[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 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.[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 human gastrointestinal 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 called oligosaccharides as well as resistant starch are the main source of prebiotics that have been identified.[8][4][9][10] 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.[7][3] Fructans are a category of carbohydrate consisting of fructooligosaccharides (FOS) and inulins, while galactans consist of galactooligosaccharides.[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 as pectin,[14] beta-glucans,[15] and xylooligosaccharides.[16]
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".[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]
Function
When the prebiotic concept was first introduced in 1995, the primary focus was on the effects that prebiotics confer on
Mechanism of action
Sources
Prebiotic sources must be proven to confer a benefit to the host in order to be classified as a prebiotic.[3] Fermentable carbohydrates derived from fructans and xylans 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]
Endogenous
An endogenous source of prebiotics in humans is human breast milk, which contains oligosaccharides structurally similar to galactooligosaccharides, referred to as human milk oligosaccharides.[26][9][22][3] Human milk oligosaccharides were found to increase the Bifidobacteria 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]
Exogenous
Indigestible carbohydrate compounds classified as prebiotics are a type of
| 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 Asparagus | 5% |
| Raw Wheat bran
|
5% |
| Whole Wheat flour, Cooked | 4.8% |
| Raw Banana | 1% |
| Source:[28] | |
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) |
| Source[28] | |
Research
Preliminary research has demonstrated potential effects on calcium and other mineral absorption,
No good evidence shows that prebiotics are effective in preventing or treating allergies.[37]
While research demonstrates that prebiotics lead to increased production of short-chain fatty acids (SCFA),[38] 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.[39]
The sudden addition of substantial quantities of prebiotics to the diet may result in an increase in
Genetic modification
Genetically modified plants have been created in research labs with upregulated inulin production.[43][44]
See also
- Antibiotic – Antimicrobial substance active against bacteria
- Mannan Oligosaccharide based nutritional supplements (MOS)– Polysaccharides formed from mannose
- Prebiotic scores– Measure of effects of prebiotics
- Probiotic – Microorganisms said to provide health benefits when consumed
- Psychobiotic – Microorganisms giving mental health effects
- Resistant starch – Dietary fiber
- Synbiotics – Nutritional supplements
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Further reading
- Frank W. Jackson, PREbiotics, Not Probiotics. 2013, Jacksong GI Medical. ISBN 978-0991102709.
External links
