Prebiotic

Prebiotics are non-digestible food ingredients that stimulate the growth and/or activity of bacteria in the digestive system which are beneficial to the health of the body. They were first identified and named by Marcel Roberfroid in 1995.^[1] They are considered a functional food.

Typically, prebiotics are carbohydrates (such as oligosaccharides), but the definition does not preclude 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 ^[2] 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 clarified that only two particular fructooligosaccharides fully meet this definition: oligofructose and inulin^[3]. Caution may be in order when referring to other substances as "Prebiotic," and it is increasingly common to refer to other similar substances as "possible" or "likely" Prebiotics in order to distinguish.

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-lenghts 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.^{[4][5][6][7][8]}

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 bacteria. 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^[9]) and the effectiveness and intrinsic strength of the immune system.^[10] 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.^[11]

Sources

Traditional dietary sources of prebiotics include soybeans, inulin sources (such as Jerusalem artichoke, jicama, and chicory root), raw oats, 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."

Jerusalem Artichoke is a frequently referred to as a rich source of prebiotic fiber. This is true, but it should be pointed out that jerusalem artichoke is NOT the traditional spiky green artichoke found in most groceries stores, but another plant altogether (and a far-from-common offering at most food merchants).

Top 10 Foods Containing Prebiotics

^[12]

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 digetive disorders. Given an average 6g serving, below are the amounts of Prebiotic Foods Required to achieve a Daily Serving of Prebiotic Fiber

^[13]

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 fructooligosaccharides (FOS), xylooligosaccharides (XOS), polydextrose and galactooligosaccharides (GOS). Some monosaccharides such as tagatose are also used sometimes as prebiotics.^{[citation needed]}

In petfood also mannooligosaccharides are being used for prebiotic purposes.

Again, one may wish to recall that Roberfroid, whom many consider the pre-eminent authority on Prebiotics^[14], states that only two specific fructooligosaccharides - oligofructose and inulin - meet his seminal definition of "Prebiotic."^[3]

Genetically engineering plants for the production of inulins has also become more prevalent ^[15].^[16], despite the still limited insight into the immunological mechanisms activated by such food supplementation ^[17].

Effects

Studies have demonstrated positive effects on calcium and other mineral absorption^[18], immune system effectiveness^[19], bowel pH, reduction of colorectal cancer risk^[20], inflammatory bowel disorders (Crohn's Disease and Ulcerative Colitis) ^[21] and intestinal regularity.^{[citation needed]} Recent human trials have reinforced the role of Prebiotics in preventing and possibly stopping early stage colon cancer.^[22] It has been argued that many of these health effects emanate not just from bifidogenic function of prebiotics, but also from increased production of short-chain fatty acids by the stimulated beneficial bacteria. Thus food supplements specifically enhancing the growth of intestinal bacteria are widely recognized to be beneficial.

While research does clearly demonstrate that prebiotics lead to increased production of these SCFA's^[23], 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-reducing 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.^{[citation needed]}

See also

• Prebiotic scores
• Probiotic

References

External links

• Food-Info.net on prebiotics and bifidogenic factors
• International Scientific Association for Probiotics and Prebiotics
• http://www.raysahelian.com/prebiotic.html
• http://www.duphalac.com/patienten/prebioticeffect/0,,10296-2-0,00.htm
• http://www.prebiotin.com/index.php?option=com_content&view=article&Itemid=48&id=27 Extensive listing of Prebiotic-related research.
• http://www.jacksongi.com/wonderful_colon.aspx
• http://www.isapp.net/docs/Consumer_Guidelines_prebiotic.pdf
• http://www.bodyecology.com/07/02/08/prebiotics_essential_to_heart_health.php
• http://www.sciencedaily.com/releases/2008/06/080627163121.htm
• http://www.sciencedaily.com/releases/2008/04/080401200444.htm
• http://www.prebiotic.ca/prebiotic_fibre.html
• http://www.dailymail.co.uk/health/article-400681/The-facts-prebiotics.html
• http://www.innvista.com/health/nutrition/biotics/prebiot.htm
• http://www.ngrguardiannews.com/natural_health/article01/indexn2_html
• http://books.google.com/books?id=y2rvBwMy6HgC&printsec=frontcover#PPA43,M1
• http://books.google.com/books?id=XgF_VEDw-REC&printsec=frontcover