Gut Health & the Microbiome - Fact vs. Fiction

An Expert's Perspective on the Microbiome and the Truth about Probiotic Supplements



I'm sure by now you've heard the buzzwords "microbiome" and "gut health" popping up more and more in the health and wellness community. It seems like every day there is a new sparkling drink that claims to improve our gut health but what exactly is the microbiome and how do bacteria play a role in our overall health and wellness?


Fortunately, I was able to talk to Sam Light, PhD, an assistant professor at the Department of Microbiology at the University of Chicago. His lab researches the effect of metabolism within the gut microbiome on human health so he was able to bring a lot of light to the topic for me and all of you!


Read our Q&A below for all of the answers to your gut health questions!



1. What exactly is the "microbiome" that so many health and wellness experts are talking about?


The microbiome typically refers to non-pathogenic microbes that are adapted for life on/in the human body. Different microbes reside on distinct parts of the body, with some of the major sites being the gut, mouth, skin, and vagina. Of these regional microbiomes, the gut microbiome is the best studied and contains the most microbes. Trillions of microbial cells and hundreds of microbial species make the gastrointestinal tract their home. Most of these microbes are located in the large intestine, with fewer cells in the small intestine and stomach.


Members of the microbiome coevolved with animals to contribute to digestion. Components of food that evade digestion in the small intestine are acted upon by the microbiome in the large intestine. The products of the microbiome’s digestive activities are absorbed and can account for up to 10% of acquired calories. The microbiome can be considered a microbial organ, connected to the rest of the body, that impacts health in a myriad of different ways.


2. What is the difference between "good" and "bad" bacteria in the gut?


It’s hard to say. “Good” and “bad” typically refer to some fashion in which the bacteria impact health in a positive or negative way. While the bacteria that consistently cause disease can be considered “bad,” the distinction between good and bad isn’t so clearcut for the majority of the members of the microbiome and may be context dependent.


3. What are pro and prebiotics and what is their role as far as our gut health goes?


Probiotics are supplements that contain living microbes. Prebiotics are dietary supplements that feed (and drive the growth of) particular members of the microbiome.



4. How does the health of our gut relate to our overall health and immune system?


The microbiome impacts health in a variety of ways. For example, microbiome deficiencies have been linked to several autoimmune disorders, the efficacy of cancer-targeting immunotherapies, and many other conditions. The effects of the microbiome are generally either due to roles in educating the immune system or its digestive capabilities. The digestive action of the microbiome on dietary components generates many drug-like small molecules that can enter the bloodstream and impact health in different ways.


5. In your opinion, has the widespread usage of antibiotics led to an epidemic of gut related health issues such as Crohn's, and irritable bowel syndrome (IBS)?


Something has led to an increased incidence of Crohn’s, IBS, and a variety of other disorders in industrialized countries. The microbiome is clearly linked to some of these. The gut microbiome is definitely a major factor in IBS. The evidence for Crohn’s is more equivocal. It’s hard to say how much antibiotics overprescription is driving this. A variety of other lifestyle differences (dietary, exposure to unspecified chemicals, etc.) may be more relevant.



6. Do probiotics in supplement pill form even reach the gut?


Many of the common probiotics do not colonize the gut and are quickly flushed out. Also, because of lax regulation, many available probiotics do not contain living microbes or what is claimed on the label.


There is good reason to be skeptical of probiotic supplements. In addition to the unreliability of many of the manufacturers, there isn’t strong scientific evidence to support claims about the health-promoting properties of most common probiotics.

The history of probiotics is quite fascinating and illuminating. The original idea for probiotics is over 100 years old and was popularized by the celebrated scientist Élie Metchnikoff. Metchnikoff thought that the gut microbiome contributed to disease and that probiotics might promote health by inhibiting the microbiome. He was wrong on both counts. Nevertheless, some of the same probiotics that he introduced remain popular to this day.


7. So if we can’t absorb “probiotics” via supplement form, then the best/only way to get pro and prebiotics is via our diet? How do we colonize the bacteria in our gut to begin with and what factors are most important when it comes to “rebuilding” our gut after say taking a long bout of antibiotics?


Well, first off, “absorb" is not exactly the right word. The microbiome’s (or, in theory, a probiotic's) digestive products, not the microbes themself, are absorbed by our intestinal cells. The microbes remain within the gut.

There are microbes all around us that seed the microbiome shortly after birth or later in life. The concept of a probiotic — providing lacking but beneficial microbes — is a good one. It’s more just a problem with the current options. Hopefully, better options will one day exist and, at least to start, will be routinely provided to patients post antibiotic treatment.

In terms of prebiotics, a lot can fall into this category. Fruits and vegetables feed your microbiome and so, if you have a healthy diet, you’re likely already getting sufficient prebiotics. If you don’t have a healthy diet or in other specific instances a prebiotic supplement may make sense.


8. How much does our diet influence gut health? Are there certain things we should avoid in order to obtain a healthy microbiome? Diet impacts the microbiome and gut health quite a bit. Regularly consuming fiber-containing foods, like fruits and vegetables, is probably the most important thing for maintaining a healthy microbiome. There is evidence that unidentified components in some highly processed foods are bad for the microbiome and so that’s one thing to avoid.

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