Prebiotics—What They Are & Why You Need Them

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Chances are, you’ve heard about probiotics. They’re the healthy bacteria that you can get through foods or supplements that crowd out the unhealthy bacteria in your gut—supporting everything from digestion, to regularity, immune health, and more.

But what about prebiotics? If you want to fully support your gut—and ensure a healthy balance of bacteria—prebiotics are one of the most important substances you can eat and/or take daily. Yet, unfortunately, most people don’t get enough.

What Is a Prebiotic?

We used to think probiotics, in addition to a healthy diet, were all that the gut needed to promote diversity and healthy levels of “good” bacteria and yeasts. Now, we’re learning more about the important role prebiotics play in supporting the growth and functionality of probiotics in the gut.

Specifically, prebiotics are a special type of fiber your body can’t digest. Therefore, they’re able to make its way to your large intestine without being broken down by the acids in your stomach.

In your intestines, prebiotics feed and fuel the good bacteria. I like to think of them as the “fertilizer” that allows the healthy bacteria in your gut to thrive and multiply. As prebiotics pass through the digestive tract they are eventually broken down into short-chain fatty acids (SCFA).

The Role of SCFAs in Gut Health

SCFAs—including acetate, butyrate, and propionate—serve many functions in the gut. One of their most important roles is supporting the protective barrier that separates your gut from your bloodstream, keeping foreign invaders out and preventing issues like leaky gut syndrome.

SCFAs also help to lower the pH (acidity) level in your colon, which creates an environment that allows the good bacteria that support your health to thrive. They can also help to stimulate T-regulatory cells, which can help to modulate the immune system.

As you can see, the breakdown of prebiotics into SCFAs plays a major role in supporting optimal gut health by helping to support the growth of the “good” bacteria in your gut. Research also suggests prebiotics not only support gut health, but often have far-reaching benefits in the body, including supporting your brain, mood, memory, and more.

Examples of Prebiotic Foods

The official definition of a prebiotic is “a substrate that is selectively utilized by host microorganisms conferring a health benefit.”

What I like to say is that prebiotics usually fall into the carbohydrate category. And due to the products produced when your body breaks them down—such as SCFAs—they support the growth and diversity of probiotics in the gut, improving your health.

It seems that other compounds like polyphenols may eventually be grouped into the prebiotic category, but for now carbohydrates are the main source of prebiotics.

Examples of good prebiotic-rich foods include garlic, onions, leeks, artichokes, asparagus, bananas, dandelion greens, sugar beets, Jerusalem artichokes, and apples. There are certain resistant starches such as cooked then cooled potatoes and rice, green plantains, or lentils that are considered prebiotic foods as well. Yet, it can be tough to get enough prebiotics through food sources alone, so I recommend also taking a good prebiotic supplement.

What Are the Best Prebiotic Supplements?

We all strive to get everything we need from our diet, but sometimes people don’t eat enough prebiotic-rich foods. This is where supplements that contain prebiotics are useful.

Prebiotic supplements come in several forms:

  • FOS Prebiotics: Fructooligosaccharides (FOS) are a special form of carbohydrates used as a sweetener in some foods. One of its benefits is that it doesn’t raise your blood sugar as other sweeteners can. As a prebiotic, FOS promotes the growth of good bacteria in your gut. Sometimes if there is an underlying dysbiosis (such as an imbalance in gut flora), people may initially develop some gas and bloating. Yet, over time and with a shift in the makeup of your gut bacteria, these symptoms usually subside.
  • GOS Prebiotics: Galacto-oligosacchardies (GOS) is a sugar found in dairy products, beans, and certain types of root vegetables. It’s sometimes used with infants to help prevent constipation and certain types of allergies. As a prebiotic, it helps to feed and strengthen probiotics. Like FOS, and particularly if there is an underlying gut issue present, GOS can cause temporary stomach cramps, diarrhea, gas, and bloating. With time, most people can tolerate GOS in low doses.
  • Inulin Prebiotics: This prebiotic is found in some plant-based foods—such as asparagus, bananas, and garlic. In supplement form, it usually comes from the chicory root. It’s been found to help with colon health and reducing constipation. As with FOS and GOS, side effects can include gas, loose stools, abdominal cramping, and bloating.
  • XOS Fiber: A relative newcomer on the block, XOS is a special non-digestible fiber from non-GMO corn. As a prebiotic, it helps to energize and promote the growth of beneficial bacteria in the gut, including the important bifidobacteria form. What I like about XOS is that unlike other forms of prebiotics, it seems to be better tolerated—with fewer side effects.

In summary, if you want to support your healthy gut bacteria and overall good health, I recommend including prebiotic-rich foods in your diet and supplementing if prebiotic foods are limited.

It’s not uncommon for people to initially react to prebiotics as the balance of gut bacteria adjusts. Plus, inadvertent fermentation of prebiotics can sometimes lead to symptoms like gas and bloating. Often it takes a few days for symptoms to subside, but if you don’t feel well while eating prebiotic foods or taking prebiotic supplements, reduce the dose or discontinue them entirely.

I find that a fair amount of folks with irritable bowel syndrome (IBS) or inflammatory bowel disease (IBD) cannot tolerate prebiotic foods or supplements, and sometimes treating the underlying condition can help to minimize the side effects of prebiotics.

Dr. Drew Sinatra

Meet Dr. Drew Sinatra

Dr. Drew Sinatra is a board-certified naturopathic doctor and self-described “health detective” with a passion for promoting natural healing, wellness, and improving quality of life by addressing the root cause of illness in patients of all ages. His vibrant practice focuses on treating the whole person (mind, body, and spirit) and finding missed connections between symptoms and health issues that are often overlooked by conventional medicine.

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