Gut Feelings: Probiotics & Mental Health

Michael Greger M.D. FACLM · May 31, 2013 · Volume 13

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We’ve known our mental state can affect our gut flora, but might our good bacteria be affecting our mental state?

Discuss

Transcript

Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.

Before Thorazine was invented in 1950, mental illness was often treated surgically. In fact, in 1949, the inventor of the lobotomy was awarded the Nobel Prize. But, before tens of thousands were lobotomized, colectomy was all the rage. There was this theory that bad bacteria in the gut—”intestinal putrefaction”—was the cause of mental illness. So, the cure was to just surgically remove the colon. Yes, the surgery killed about one in three. But, when they didn’t die, surgeons bragged that (for example) when he resected the colons of schoolchildren as a preventive measure, there was a “cessation of abnormal sex practices, such as masturbation”—which was viewed at the time as a precursor for mental illness later in life.

There were others, though, that took less drastic approaches, suggesting one could instead treat this intestinal putrefaction by changing the intestinal flora. So, over a century ago, there were reports of successfully treating psychiatric illnesses, like depression, with a dietary regimen that included probiotics. Doctors perceived a connection between depression and “feces deficient in quantity and moisture and very offensive in odor.” So, they gave patients probiotics. And, not only did people feel better psychologically, but their “feces increase in quantity, become softer, and of regular consistency, and the offensive smell diminishes.” Concurrent with the probiotics, however, all patients were started on a vegetarian diet, so it may not have been the probiotics at all.

This field of inquiry remained dormant for about a hundred years, but a new discipline has recently emerged known as “enteric [meaning intestinal] neuroscience.” Our enteric nervous system—the collection of nerves in our gut—has been referred to as our “second brain,” given its “size, complexity, and similarity.” We’ve got so many nerves in our gut that, as many as in our spinal cord. And, it kinda makes sense. The size and complexity of our gut brain is not surprising when considering the challenges posed by the interface with “our largest body surface.” We have a hundred times more contact with the outside world through our gut than through our skin. We also have to deal our 100 trillion little friends down there. Takes a lot of processing power.

Now, anyone who’s ever gotten butterflies in their stomach knows that our mental state can affect our gut. In fact, everyday stressors can affect the integrity of our gut flora. This innovative study looked at feces scraped from used toilet paper in undergrads during exam week. This is how many bacteria they had in their feces before the exam. But, look what happens on exam day—and, in fact, lasted through the whole week. So, our mental state can affect our gut. But, can our gut affect our mental state? We didn’t know, until recently.

For example, many suffering from chronic fatigue syndrome “complain of gut dysfunction.” So, researchers tried giving people probiotics to see if their mental and emotional state could be improved, and indeed, it appeared to help.

What about healthy people, though? This is the study that really rocked the scientific establishment. “An assessment of the psychotropic…properties” of probiotics. One month of probiotics was found to significantly decrease symptoms of anxiety, depression, anger, and hostility. How is that possible? Well, a variety of mechanisms has been proposed for how intestinal bacteria may be communicating with our brain.

Until that study was published, though, the idea that probiotic bacteria administered to the intestine could influence our brain seemed almost surreal. Like science fiction. Science, yes; but fiction, no. “Likely, organisms already inside us carry out some degree of influence on our mental wellbeing.”

So, might people suffering from certain forms of mental health problems benefit from a fecal transplant from someone with a more kind of happy-go-lucky bacteria? We don’t know, but this ability of probiotics to affect brain processes “is perhaps one of the most exciting recent developments in probiotic research.”

Please consider volunteering to help out on the site.

Sources

Acknowledgements

Images thanks to KayVee.INC, Père Ubu & NaustvikPhotography.com via flickr; and Bonkers Institute

Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.

Before Thorazine was invented in 1950, mental illness was often treated surgically. In fact, in 1949, the inventor of the lobotomy was awarded the Nobel Prize. But, before tens of thousands were lobotomized, colectomy was all the rage. There was this theory that bad bacteria in the gut—”intestinal putrefaction”—was the cause of mental illness. So, the cure was to just surgically remove the colon. Yes, the surgery killed about one in three. But, when they didn’t die, surgeons bragged that (for example) when he resected the colons of schoolchildren as a preventive measure, there was a “cessation of abnormal sex practices, such as masturbation”—which was viewed at the time as a precursor for mental illness later in life.

There were others, though, that took less drastic approaches, suggesting one could instead treat this intestinal putrefaction by changing the intestinal flora. So, over a century ago, there were reports of successfully treating psychiatric illnesses, like depression, with a dietary regimen that included probiotics. Doctors perceived a connection between depression and “feces deficient in quantity and moisture and very offensive in odor.” So, they gave patients probiotics. And, not only did people feel better psychologically, but their “feces increase in quantity, become softer, and of regular consistency, and the offensive smell diminishes.” Concurrent with the probiotics, however, all patients were started on a vegetarian diet, so it may not have been the probiotics at all.

This field of inquiry remained dormant for about a hundred years, but a new discipline has recently emerged known as “enteric [meaning intestinal] neuroscience.” Our enteric nervous system—the collection of nerves in our gut—has been referred to as our “second brain,” given its “size, complexity, and similarity.” We’ve got so many nerves in our gut that, as many as in our spinal cord. And, it kinda makes sense. The size and complexity of our gut brain is not surprising when considering the challenges posed by the interface with “our largest body surface.” We have a hundred times more contact with the outside world through our gut than through our skin. We also have to deal our 100 trillion little friends down there. Takes a lot of processing power.

Now, anyone who’s ever gotten butterflies in their stomach knows that our mental state can affect our gut. In fact, everyday stressors can affect the integrity of our gut flora. This innovative study looked at feces scraped from used toilet paper in undergrads during exam week. This is how many bacteria they had in their feces before the exam. But, look what happens on exam day—and, in fact, lasted through the whole week. So, our mental state can affect our gut. But, can our gut affect our mental state? We didn’t know, until recently.

For example, many suffering from chronic fatigue syndrome “complain of gut dysfunction.” So, researchers tried giving people probiotics to see if their mental and emotional state could be improved, and indeed, it appeared to help.

What about healthy people, though? This is the study that really rocked the scientific establishment. “An assessment of the psychotropic…properties” of probiotics. One month of probiotics was found to significantly decrease symptoms of anxiety, depression, anger, and hostility. How is that possible? Well, a variety of mechanisms has been proposed for how intestinal bacteria may be communicating with our brain.

Until that study was published, though, the idea that probiotic bacteria administered to the intestine could influence our brain seemed almost surreal. Like science fiction. Science, yes; but fiction, no. “Likely, organisms already inside us carry out some degree of influence on our mental wellbeing.”

So, might people suffering from certain forms of mental health problems benefit from a fecal transplant from someone with a more kind of happy-go-lucky bacteria? We don’t know, but this ability of probiotics to affect brain processes “is perhaps one of the most exciting recent developments in probiotic research.”

Please consider volunteering to help out on the site.

Images thanks to KayVee.INC, Père Ubu & NaustvikPhotography.com via flickr; and Bonkers Institute

Doctor's Note

This closes out my four-part video series on the latest in probiotic science. I began with the two most established indications for their use in Preventing & Treating Diarrhea with Probiotics, then moved onto a more speculative use in Preventing the Common Cold with Probiotics? I then offered practical advice on how to best take probiotic supplements in Should Probiotics Be Taken Before, During, or After Meals?.

Update: In 2017, I released a new video on probiotics. See: Culture Shock – Questioning the Efficacy and Safety of Probiotics.

The colon removal story reminds me of the mastectomies they used to do for breast pain (see Plant-Based Diets For Breast Pain).

Why might a vegetarian diet alone have improved mood? Check out Improving Mood through Diet—as well as my serotonin series that starts with Human Neurotransmitters in Plants.

More on treating chronic fatigue syndrome in:

What else might our good bacteria be doing for us? They may be helping with weight control (see Fawning over Flora), and serving up anti-cancer compounds! See Flax & Fecal Flora, and Sometimes the Enzyme Myth is True.

For more context, check out my associated blog posts: Probiotics & Diarrhea; How Should I Take Probiotics?; How Probiotics Affect Mental Health; and Top 10 Most Popular Videos of 2013.

What are The Benefits and Side Effects of Probiotic Supplements? Check out the video.

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