In many clinical studies, probiotics may be combined with prebiotics. What are prebiotics? If the term “prebiotics” is unfamiliar, don’t be alarmed. Prebiotics are a relatively new thing with the first formal definition being coined in 1995 and the current definition introduced in 2004. Prebiotics are ‘‘selectively fermented ingredients that allow specific changes, both in the composition and/or activity in the GI microflora that confer benefits upon host wellbeing and health.’’ In simpler terms, this means that prebiotics are food for beneficial bacteria and can be used to encourage the growth of certain bacterial species.
The most popularly studied prebiotics are indigestible polysaccharides. Polysaccharides are the formal term for complex sugar molecules such as starch. “Poly” means “many” and “saccharide” refers to the most simple carbon atom ring with water molecules bound to the carbons (see figure for an example). All sugars, from common table sugar to starch, are made up of chains of these monosaccharide units. What makes some digestible for humans and others indigestible is the type of bonds that are formed between the monosaccharides.
An example of an indigestible polysaccharide is cellulose found in wood and other plants. Using prebiotics, however, is not about eating wood. Prebiotics are classified into short chain oligosaccharides consisting of 3-9 monosaccharide units and long chain polysaccharides, which have more than 10 units. These are found in a number of vegetables that we normally eat and in human breast milk. Food sources of prebiotics are chicory root, Jerusalem artichoke, dandelion greens, garlic, leek, asparagus, onions, and bananas. These plants use these molecules, called inulins, as a form of nutrient storage. In breast milk, it is speculated that prebiotic polysaccharides are present to ensure that the intestinal bacteria of infants is enriched with beneficial bacteria.
Though the effect of prebiotics on probiotics is highly emphasized, it is also recognized that prebiotics can have some influence on the gut directly. Some studies using isolated intestinal epithelial cells have found that exposure to prebiotics leads to modulation of the immune response.
A number of prebiotics are now being studied and used in clinical trials to determine their prebiotic effect (ability to change the bacterial composition in the gut). Also prebiotics are a main staple in baby formula, where they are used to help boost the immune system, protecting the infant from allergies and dermatitis. This was a practice formally initiated in Japan to help formula appear more as breast milk.
When searching for probiotics you may come across a number of brands packaged with prebiotics. The most commonly found prebiotics are inulin, lactulose, fructo-oligosaccharide (FOS), β-galacto- oligosaccharides (GOS) and Trans-galactooligosaccharides (TOS). Inulin is found in plants and is used as a precursor for the production of GOS and FOS. Lactulose is known to support the growth of Bifidobacteria and Lactobacilli. It also is known to have a laxative effect. FOS and GOS are found commonly in baby formulas. They support the growth primarily of Bifidobacteria and inhibit harmful species like Bacteroides and Clostridia. TOS is also well known for encouraging Bifidobacterial growth.
Prebiotics can be useful complements to a health program including probiotics. However, some caution should be advised regarding their use in those with chronic intestinal inflammation. Although prebiotics are known to stimulate beneficial bacteria, it’s still unknown precisely what other bacterial species they can feed. Prebiotics could still have the potential to feed (and increase the growth of) harmful bacteria. In those with chronic inflammation, the gut is usually unable to control its own bacteria populations. By introducing prebiotics, one could, unintentionally, cause the unchecked growth of something harmful. Please consult your personal doctor or nutritionist for more information.
Disclaimer: This article is not intended to provide medical advice, diagnosis or treatment.
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