Prebiotics & Gut Health {+ Kimchi Recipe}

What Are Prebiotics?

Prebiotics have been gaining a lot of attention lately due to their impact on the health and diversity of the gut microbiome. Researchers and nutritionists in the mid-1990’s discovered prebiotics as they observed that certain soluble fibers such as inulin, oligofructose and fructo-oligosaccharides caused remarkable changes in the bacterial composition of the colon. Today, the International Scientific Association of Probiotics and Prebiotics (ISAPP) defines “dietary prebiotics” as “a selectively fermented ingredient that results in specific changes in the composition and/or activity of the gastrointestinal microbiota, thus conferring benefit(s) upon host health." (1) In other (less scientific) words, prebiotics are fermentable dietary fibers that serve as nutrition for resident gut bacteria resulting in improved digestive, cardiovascular, cognitive, neurological and immune system health.

Health Benefits of Prebiotics

Prebiotics play an important role in human health. They naturally exist in breastmilk (to seed the gut of a newborn baby with healthy microbes) as well as in various plant foods (fructo and galacto-oligosaccharides). The best food sources of prebiotics are asparagus, leeks, garlic, onion, okra, artichokes, barley, rye, peas, beans, and seaweed.

As intestinal bacteria munch on prebiotic fibers, which human digestion is unable to fully break down, they release short-chain fatty acids (SCFAs). SCFAs include lactate, acetate, butyrate, and propionate which increase the acidity of the colon (lower the colonic Ph), improve intestinal absorption, and modulate the innate immune system to better defend the host against pathogenic organisms.

Short-chain fatty acids are also beneficial for improving the integrity of the gut lining. Butyrate in particular serves as a substrate (food) for colonocytes (cells lining the large intestine) and is involved in the development of the intestinal epithelium: a one-cell thick protection layer separating the intestinal lumen from the rest of your body preventing foreign substances like microbes, undigested food particles, and toxic molecules from entering the circulation. (2),(7)

The short-chain fatty acids produced from the digestion of prebiotic fibers by intestinal bacteria are molecules small enough to diffuse through the gut lining and enter the bloodstream exerting their protective, anti-inflammatory effects not only on the gastrointestinal system but on other organ systems in the body as well including the central nervous system, immune system, and cardiovascular system. (4),(5),(6)

The health benefits associated with eating a diet high in prebiotic fibers are diverse and can include improved digestive and cognitive function as well immune modulation through increased production of immunoglobulins and sIgA (secretory IgA is a gut-specific immune function marker), increased production of immuno‐regulatory cytokines, and a reduction in pro‐inflammatory cytokines.(2),(7)

Types of Prebiotics

Prebiotics are a type of fermentable soluble fiber. Although not all prebiotics are considered carbohydrates, the majority of them are a subset of carbohydrate groups called oligosaccharide carbohydrates (OSCs). The most known and researched prebiotics are fructo-oligosaccharides (FOS), including inulin or oligofructose, galacto-oligosaccharides (GOS), and trans-galacto-oligosaccharides (TOS). (1),(2)

Non-carbohydrate types of prebiotics are flavonols, a type of plant pigments with anti-oxidant properties found in fruits and vegetables, tea, and raw cacao beans.

Resistant Starch {RS}

Resistant starch is another type of prebiotic, which has been shown to stimulate the growth of butyrate producing bacteria in the colon. As mentioned earlier, butyrate is a type of short-chain fatty acid that preserves the integrity of the intestinal mucosa and has anti-inflammatory properties. RS includes the portion of starch that can resist digestion by human pancreatic amylase (enzyme responsible for breaking down carbohydrates) in the small intestine and thus, reach the colon intact.(3) RS is found in many plant foods, including grains, root vegetables (especially potatoes), legumes, seeds, and some nuts. Fruits like bananas and mangoes are also a great source of resistant starch in their unripe or green state when the simple sugars (fructose, sucrose and glucose) are very low while RS constitutes the largest portion of the fruit (50-80%).

Consumption of resistant starch has been associated with improved insulin resistance and post-prandial glucose response (minimizing blood glucose spikes), which may have beneficial implications in the management of diabetes, and is associated with a decrease in the levels of cholesterol and triglycerides. Other benefits of RS consumption are "increased fecal bulk and bowel movement frequency, prevention of constipation and hemorrhoids, decreased production of toxic and mutagenic compounds, lower colonic pH, and ammonia levels."(3)

A Word of Caution

Since human enzymes cannot break down prebiotic fibers, they are transported to the colon and fermented by gut bacteria. The observed side effects of prebiotic consumption or supplementation are mostly due to increased levels of fermentation and resulting osmotic pressure. There are occasionally negative symptoms of consuming prebiotics, the most commonly reported being diarrhea, bloating, cramping, and stomach pain.