Prebiotics, Probiotics, and the Gut Microbiota: What You Need to Know For Your Health

Prebiotics, Probiotics, and the Gut Microbiota: What You Need to Know For Your Health

When it comes to our health, much has been discovered about the bacteria living in our gut. Research has connected allergies, obesity, diabetes, chronic inflammation, and many other illnesses and diseases, to the health and diversity of our gut microbiota. Keeping your gut bacteria healthy comes down to the probiotics and prebiotics we ingest.

Before we get to the importance of pre- and probiotics, I want to be sure that you have a fundamental understanding of your microbiota:

Microbiota vs. Microbiome

The microbiota refers to the microbes living on and in our bodies while the microbiome refers to the genetic information these microbes carry. Estimates have our body’s bacteria out numbering our body’s own cells by about 3:1, but new data suggests that these numbers are actually lower, more like 1:1. Still, we have at least as many bacterial cells in and on our body as we do our own cells. While these bacteria can contribute to our overall health by the functions they carry out, they can also contribute to our health by the genes or genetic information that they carry. You can think of your microbiome as an extension of your own genetics.

The gut is rich with bacterial life; everywhere from our mouth through to our colons (large intestines). But when we talk about the health benefits of the gut microbiota we are almost exclusively referring to the bacteria that resides within the large intestines. When we eat food the digestion process progresses at differing rates dependent upon what digestive organ is at work. Food passes fairly rapidly from the stomach and small intestines, usually in a matter of hours. However, by the time the undigested portions of food reach the colon its processing slows significantly. This is important because the longer retention time allows the bacteria in our colons to have access to the undigested foods and carry-out interactions with the immune system that can significantly impact our health.

A tremendous amount of our immune system can be found in the lining of our intestines. Many of the functions and gene products of the gut microbiota are communicated through the immune system. Since the bacteria remain in the hollow of the intestines, not actually passing into the body, they influence our health by the chemical signals they make. The signals act as information to the immune system. The immune system is involved in all diseases through the process known as inflammation. One of the major ways in which the gut bacteria impacts our health is through the influence they have on inflammation, mediated through the immune system.

Having the right, healthy gut bacteria is important for maintaining your health and preventing disease. How do we get them and keep them healthy? Prebiotics and probiotics of course!


Prebiotics vs. Probiotics

Probiotics are ingested bacteria that are capable of influencing your own gut microbiota while prebiotics are the foods your gut bacteria thrive on. You are probably very familiar with probiotics and likely associate them with products like yogurt, kefir, sauerkraut and other fermented foods. Prebiotics may be less familiar to you, but they are derived from plant foods like fruits, vegetables, legumes, nuts/seeds, and whole grains. Probiotics have been hyped in the media because there are many commercial products that tout the benefits of their added probiotics. It has led to a bias towards probiotics while I’d argue that prebiotics are even more important for our health.


There is a body of evidence that dietary probiotics can influence our health. This set of data however is mostly derived from studies done using unhealthy patients with gastrointestinal diseases. Examples of this include treating diarrhea in babies, reducing the severity of symptoms associated with IBS/IBD in adult patients, and the treatment of gut-specific infections. While we think of probiotics as food-specific, it’s important to note that probiotics really refers to any bacteria influencing our own microbiota; this is where the real power of probiotics plays into our health.

A tremendous effort is underway to understand what gut bacteria make for a health individual. By defining this status then unhealthy gut microbes can be modulated by the addition of other healthy bacteria. Bacteria have their own world where they work with or against one another. They have the ability to communicate with other bacteria, working in synergy or they can eliminate one another. Knowing what bacteria will work to eliminate the bad bacteria can help us fight disease. One early and simple example of this is fecal transplants for the treatment of a difficult-to-treat gut bacteria C. difficile. Yes, you read that right, fecal transplants. Poop is taken from a non-infected individual with a presumably healthy gut microbiota and transferred to the C. difficile infected individual. This helps cure the infection. This approach is being considered for a whole host of conditions and diseases, from obestiy to the treatment of Crohn’s disease. Fortunately, many companies are looking at ways to isolate the good, poop bacteria and make it in a pill form (sans poop!).

Probiotics work best when a well defined population of bacteria is used to influence a population of disease-causing bacteria. This of course is the intense focus of many academic labs, biotech and pharmaceutical companies working to develop probiotic “drugs.” So what about the probiotics in your yogurt? Well, we do know that these probiotics don’t take up residence in your colon but act by influencing the bacteria that are already in your gut. No one can seem to explain how as of yet, but it is assumed that it’s through bacteria-bacteria communication and communication with the gut immune system. Probiotics in our foods have the capacity to influence our immune systems and our gut microbiota but in this form, their impact on disease is limited.


Now we come to the prebiotics. I’m sure, having read this far, you understand that having the right bacteria in your gut is very important. How we get the right populations is through the foods we eat. Plant-based foods aren’t only good for our general health, they’re also good for the health of our gut microbiota. The bacteria in our colons thrive on undigested plant-matter or fiber. This is what prebiotics are, food for our gut bacteria in the form of fiber. What happens if you don’t feed your gut bacteria the right foods? They die! Like any living thing. What you eat, and therefore feed your gut bacteria, influences what types of bacteria “grow.” Foods can also influence the type of information the gut bacteria relays to the immune system, for good or bad.

Eating a diet high in processed foods, fats, and sugar all influence the gut microbiota in a negative way by promoting populations of bacteria that are pro-inflammatory predisposing us to disease. Eating a diet rich in vegetables, fruits, seeds/nuts, legumes and whole grains, provides the right kind of prebiotics to feed bacteria associated with anti-inflammatory behaviors (ie. chemical signals). If you’re eating an average American diet, high in processed foods, but eating yogurt daily, it may not do much for you since the bacteria your gut harbors are likely the unhealthy type and probiotics from our diet aren’t going to reverse that. The hope is that engineered probiotics will, but that’s still in the future. What’s critical to your health is that you establish a healthy population of bacteria and then feed them well.

A Healthy Combination

The hype around probiotics has many people thinking probiotics can do more for their health than is really true. And sadly, few people know about the health benefits of prebiotics in establishing and maintaining a healthy gut microbiota. Maintaining a healthy gut microbiota means avoiding processed foods and those high in sugar and fats and eating more plant-based foods high in fiber. Bacteria adapt rapidly and data suggests that highly processed foods eaten regularly or even sporadically can derail the gut bacteria, sending it towards an unhealthy bias.

Fiber, fiber, fiber…it doesn’t just keep you regular, it makes for a healthy gut microbiota! Fiber, undigestible plant matter, is what healthy bacteria thrive on. We eat way too little. How do we get more? Eat more plant-based foods. You can take supplements but while these supply bulk, they often lack the diversity of fiber found in plants and likely preferred by the gut bacteria. So try to get more of your fiber directly from your diet.

Having a healthy gut bacteria population can be further supported by the addition of probiotics. Add in probiotics in whatever form you prefer; yogurt, kefir, sauerkraut, kombucha or other fermented foods. By eating foods high in both prebiotics and probiotics, you’ll be well on your way to establishing a healthy gut that supports your health.

Until next time, stay well!

Dr. Tobi Schmidt

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