Prebiotics and probiotics are vital to maintaining a healthy gastrointestinal (GI) system. Although probiotics get most of the spotlight, the health benefits of prebiotics are beginning to shine as research reveals how vital they are to your gut health and overall wellbeing.  

Prebiotics Versus Probiotics

Even though prebiotics and probiotics sound similar, the two play different roles in your health. Probiotics are foods or supplements that contain microorganisms that directly add to the population of healthy microbes in your gut. Common probiotic foods include yogurt, kefir, kombucha, and sauerkraut.1

Prebiotics are foods or supplements you eat that, in turn, feed the good bacteria in your digestive system. The lining of your gut, like every surface of your body, is covered in microscopic organisms –  mostly bacteria. Collectively, these organisms create a micro-ecosystem called the microbiome. And although you might not notice its presence, the microbiome plays a fundamental role in fighting disease and keeping you well. The healthier it is, the healthier you are.1,2

The key to a healthy microbiome is properly nourishing the 500-1,000 different species of bacteria that inhabit your gut.

Enter the prebiotic.

The Mighty Prebiotic

Prebiotics are typically high-fiber foods, including resistant starches. Resistant starch can't be digested in the small intestine, so it passes into the large intestine. An internet search will yield dozens of examples. Fiber-type prebiotic foods include whole grains, vegetables (garlic, onions, greens, and Jerusalem artichokes are among the best), and fruits. Common foods high in resistant starch include raw potatoes, cooked and then cooled potatoes, green bananas, legumes, cashews, and raw oats.3 

Neither resistant starches nor other fibers are digested by your body. Instead, they pass through your stomach and small intestine to your colon where they feed the friendly gut bacteria before they exit your body.3 

Not all fibrous or starchy foods are prebiotics, however. The official definition of prebiotics is food that is fermented by bacteria in the gut "that results in specific changes in the composition and/or activity of the gastrointestinal microbiota, thus conferring benefit(s) on host health.”3,4 

In other words, to qualify as a prebiotic, a food must benefit the microbes that live in your gut, which in turn, benefits you.

When the bacteria in your gut digest prebiotics they produce several compounds, including three short-chain fatty acids (SCFA) – acetate, butyrate, and propionate. These three organic compounds represent 90-95 percent of all SCFAs in the colon and are crucial to keeping the gastrointestinal tract functioning properly and disease free.4-6

Because SCFAs are small enough to fit through the cellular lining of the intestines and enter the bloodstream, they can affect other organs and body systems outside the gastrointestinal tract.7,8  

Prebiotics, Gut Health, and Colon Cancer

Short-chain fatty acids have long been recognized as important compounds in maintaining a healthy gut. They provide fuel for intestinal epithelial cells that line the colon, strengthen the gut barrier, aid in intestinal mucus production, and protect against inflammation.5,9

It is also well established that a high-fiber diet is associated with a reduced risk of colorectal cancer.6,10 The production of SCFAs from resistant starches and other fiber might play a role in protecting the colon from cancer.11,12

Scientists continue to discover associations between certain chronic health conditions and a disturbance in the microorganisms in the gut. For example, inflammatory bowel diseases (IBD), such as ulcerative colitis and Crohn's disease, are consistently characterized by a low level of beneficial bacteria that ferment fiber in the colon.13,14

This information has led to a search for treatments and health solutions that utilize friendly bacteria and SCFAs. One study found that providing mice with butyrate and acetate supplements reduced bowel inflammation.14 In addition, recent research suggests that SCFAs such as butyrate, might improve symptoms of IBD in humans.13,15

At this point, it's unclear if an altered gut microbiota is the root cause of GI disorders and disease, or if the health condition itself leads to alterations in the microbiota. More research is needed to determine the cause and effect, including how modifying the gut microbiome might provide future treatment options.

Prebiotics and the Immune System

Many types of cells in the GI tract play a critical role in regulating the immune system. Research suggests that prebiotics and SCFAs might improve how the immune system functions. One example is that prebiotics influence the release of cytokines.16 Cytokines are chemicals that affect the growth of all blood cells and other cells that help the body's immune and inflammatory responses.17 Studies also show that prebiotics can decrease the population of harmful bacteria and other pathogens in the gut by increasing the population of protective bacteria, namely Lactobacilli and Bifidobacteria.3  

Prebiotics and Type 2 Diabetes

Consuming prebiotics, and the subsequent production of short-chain fatty acids, might help improve metabolic function in type 2 diabetes.

Studies indicate that SCFAs can impact blood glucose levels, decrease inflammation that then reduces insulin resistance, and influence the process that stimulates the release of insulin.18,19  

A review of 27 randomized, controlled studies evaluated the effect of prebiotics on the metabolic and inflammatory biomarkers of adults with type 2 diabetes. Nineteen studies reported that subjects showed improvements in blood glucose levels, 15 showed improved cardiovascular markers, nine reported decreases in body weight, and nine studies showed improvement in inflammatory markers.20 

Prebiotics and Heart Health

Research indicates that short-chain fatty acids can impact heart health.3 Much of what is known about the connection between the heart and prebiotics is limited to animal studies. For example, studies on mice found that both a high-fiber diet and supplementation with the SCFAs acetate and propionate significantly reduced blood pressure levels in mice.21 Another study confirmed that SCFA-producing gut bacteria were significantly fewer in rats with high blood pressure than in the control group.22 Studies in both animals and humans show that short-chain fatty acids can lower the rate of cholesterol production, thereby reducing overall cholesterol levels.23-25

It's important to note there are considerable differences in bodily functions between animals and humans. The research findings in the lab or on animals do not always apply to the human body. More long-term studies are needed to clarify and determine the potential effects of prebiotics and SCFAs on human health.

How to Keep Your Gut Microbiome Healthy 

The best way to support your gut microbiome’s production of SCFAs is to eat a high-fiber diet that includes sufficient sources of resistant starch. Whole grains are preferable to grains ground into flour because they enable your body to produce more SCFAs.26

If you’re not getting enough fiber in your diet, then you might consider taking a fiber supplement. Although these do help bulk up your stool and aid in constipation, they might not provide the same benefits to your microbiome as natural fiber sources. And keep in mind that adding too much fiber too quickly can cause intestinal gas, abdominal bloating, and cramping, so it's best to increase fiber gradually over a few weeks.27 

There are many ways to add fiber and resistant starches to your diet that will benefit the microbes in your gut and satisfy your taste buds. Plus, it's nice to know you can improve your overall health by simply altering the foods you eat. 

A Word from Thorne

In addition to adding more fiber to your diet, there are non-fiber sources of prebiotics, including extracts from green tea and certain berries – blueberry and pomegranate, for example. You can read more about it here.

References

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