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Building a Better Gut Microbiota

Building a Better Gut Microbiota

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Prebiotic, probiotic and synbiotic strategies for success

“Happiness for me is largely a matter of digestion.” ― Lin Yutang, The Importance of Living[1]

As Chinese scholar Lin Yutang observed, a healthy gut is a core component of a happy life. Each person’s gut contains approximately 38 trillion microbes, comprising hundreds of different species (collectively, the microbiota).[2],[3],[4] And we now know that a healthy gut largely depends upon having healthy gut microbiota.[5],[6] When everything is going smoothly, beneficial species dominate over the harmful ones, protecting us from indigestion, infections, inflammation, and other troubles.[2]

A healthy microbiota supports not only the gut, but also every major organ in the body including the heart,[7] brain,[8] liver,[9],[10] kidneys,[11] bones,[12] and even the skin,[13] resulting in a “glow of health.” Conversely, imbalances in the microbiota are associated with allergies, Alzheimer’s disease, asthma, autism and learning challenges, cardiovascular disease, diabetes, eczema, indigestion, metabolic syndrome, and many other ailments.[14],[15]

It stands to reason that if we can help the beneficial bacteria grow and thrive, we may be able to improve our overall health.[16] The question then becomes: can we really build a better microbiota?

How to “seed” and “feed” the microbiota

A healthy diet, balanced lifestyle, and targeted supplementation can help support the microbiota. We can “seed” the gut with beneficial bacteria by consuming fermented foods or probiotic supplements, and we can “feed” the beneficial bacteria by ingesting foods or supplements containing prebiotics and other nutrients that help them grow.

We can “seed” the gut with beneficial bacteria by consuming fermented foods or probiotic supplements, and we can “feed” the beneficial bacteria by ingesting foods or supplements containing prebiotics and other nutrients that help them grow.

Probiotics are live microorganisms that have been demonstrated to exert positive effects on health when administered in adequate amounts.[17],[18],[19],[20] They also may modify the balance of the intestinal flora, reducing levels of the microorganisms associated with dysbiosis, and restoring levels of those associated with a healthy microbiome.[21],[22] They can be obtained by eating fermented foods such as yogurt and kefir, and/or by probiotic supplementation.

You can often (but not always) find out which bacterial species are in a particular yogurt or kefir brand by reading the label. The most commonly used probiotics are species of Lactobacillus (for example, Lactobacillus acidophilus or L. acidophilus) and Bifidobacterium (for example, Bifidobacterium lactis or B. lactis.) Bifidobacterium is especially important because its abundance declines with age and antibiotic use.[23],[24] Many fermented dairy products are not fortified with Bifidobacterium, or have low concentrations of live probiotics overall, making supplementation a more reliable choice in many cases.

A great way to support a healthy microbiota, gut, and body is to consume plenty of dietary fiber.[25] Bananas, oats, artichokes, and certain other vegetables and whole grains are especially good for the gut because of their high prebiotic content.[26] Prebiotics are water-soluble fibers that boost the growth of beneficial bacteria. They are not digested by human enzymes, so they pass through the small intestine into the colon, where beneficial bacteria use them as fuel for growth.[27] In addition to prebiotics, certain other dietary nutrients including polyphenols[28] and omega-3 fatty acids[29] help stimulate the growth of “good” bacteria.

You may have heard of inulin, fructooligosaccharides (FOS), or galactooligosaccharides (GOS), all of which are prebiotics. Only non-digestible oligosaccharides that are “bifidogenic” (increase bifidobacteria) meet the criteria for prebiotics.[30],[31] However, some prebiotics are more bifidogenic than others. Most Bifidobacterium species can grow on FOS and GOS,[32],[33] but not on inulin.[31],[34]

Xylooligosaccharides: prebiotics found in bamboo

The class of prebiotics known as xylooligosaccharides[35],[36] (pronounced zy-low-all-ih-go-saccharides, or XOS) occur naturally in bamboo shoots, fruits, vegetables, milk, and honey.[37] Although XOS can be extracted from bamboo,[38] they are more economically produced by enzymatic treatment of corn cob residues.[35],[36]

The 5-carbon (pentose) structure of XOS is fundamentally different from other prebiotics; this makes XOS highly selective for bifidobacteria, which have the enzymes necessary to break down pentose sugars.[39],[40],[41],[42],[43] Several Lactobacillus species are capable of fermenting XOS to a lesser extent.[42],[44],[45] Importantly, XOS cannot be utilized by pathogenic bacteria.[39]

XOS was shown to boost Bifidobacterium numbers in vitro (in the lab) and in vivo (in the body), and to enhance the production of butyrate,[43],[46] a short-chain fatty acid associated with gastrointestinal health.[23] Butyrate is a result of cross-feeding: it is made by other beneficial bacteria that feed on the products of bifidobacteria fermentation.[23] Like a domino effect, the fermentation of XOS has other benefits: it increases mucus production by gastrointestinal (goblet) cells.[47] A healthy mucus layer helps “good” bacteria attach to the colon, while it protects against gut pathogens.[48],[49],[50]

The daily ingestion of XOS by human subjects induced significant increases in fecal Bifidobacterium counts within four to eight weeks.[46],[51],[52],[53],[54],[55] XOS supplementation also decreased the abundance of Clostridium perfringens, an opportunistic pathogen.[50],[51] The health benefits of XOS typically have been observed at one to five grams per day, a lower dose than required for prebiotics such as FOS.[34],[52],[53],[54],[56],[57]

Synbiotics with Bifidobacterium and XOS

When British scientist Glenn Gibson introduced the concept of prebiotics in 1995, he speculated as to the additional benefits if prebiotics were combined with probiotics to form what he termed synbiotics.[58] The term “synbiotic” refers to “a combination of synergistically acting probiotics and prebiotics, where a selected component introduced to the gastrointestinal tract should selectively stimulate growth and/or activate the metabolism of a physiologic intestinal microbiota, thus having a beneficial effect on the host’s health.”[59]

The term “synbiotic” refers to a combination of synergistically acting probiotics and prebiotics.

Note that the word “synbiotic” is not the same as “symbiotic”, which refers to an interaction between two different organisms living in close physical association.

Because the word “synbiotic” implies synergism, this term is reserved for products in which the prebiotic compound selectively favors the probiotic organism.[30] The combination of B. lactis with XOS fits this description. In a simulated colon model, the addition of XOS not only increased overall numbers of bifidobacteria, but produced a tenfold increase in the abundance of B. lactis.[43] The results indicate that XOS plus B. lactis would form a successful synbiotic combination.

Large controlled trials are needed to assess the clinical effects in humans, but a preliminary study suggested the synbiotic XOS plus B. lactis improved the self-reported quality of life in otherwise healthy individuals, compared to the probiotic alone.[55] XOS is well tolerated and has a long history of safe use. Because a lower dose is needed than FOS for similar beneficial effects, XOS also is better tolerated, with less gas and bloating than is commonly seen with FOS.


A healthy gut is essential for a healthy and happy life, and a healthy gut requires a well-balanced microbiota! To support your microbiota, focus on a high-fiber diet; include fermented food products such as kefir; and consider probiotic, prebiotic, and/or synbiotic supplementation to “seed” and “feed” beneficial bacteria. Prebiotics and synbiotics containing XOS are highly selective for beneficial bifidobacteria, are well-tolerated, and support an improved quality of life.


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The information provided is for educational purposes only. Consult your physician or healthcare provider if you have specific questions before instituting any changes in your daily lifestyle including changes in diet, exercise, and supplement use.

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