Are Probiotics A Panacea Or Pure Hype?: The Gullible Gastroenterologist Weighs In

Please allow me to introduce myself.  I am the Gullible Gastroenterologist.  I’ve been around for a long long year, and today I have been given the opportunity by my good friend, the Skeptical Cardiologist (SC), to guest-blog on issues involving the GI tract.
As opposed to my skeptical friend, I had been very trusting by nature. But the SC has opened my eyes to the importance of fact-based medicine.  Seems to be a pretty good way to treat patients while making informed decisions based on the facts.
When the SC approached me to comment about probiotics, I jumped at the chance.  What could possibly be easier than discussing the obviously positive effects associated with ingesting good bacteria?  I mean, it says “good” right there in the description!  But then I remembered the SC’s insistence on giving weight to the facts.  And that’s when things started to get a more problematic.

What Are Probiotics?

Probiotics are defined by the World Health Organization as “live microorganisms that when administered in adequate amounts confer a health benefit on the host.”  The hope is that these ingested microorganisms will somehow affect the bacterial environment (the flora or microbiota) that already exists in our digestive tract.  This sounds great in theory, but it is important to realize that this issue is far from straight forward.
Go look in the mirror right now.  No seriously.  Do it.  I’ll wait.  I’m going to guess that you saw a human being in front of you (I hope).  Think about all the cells that made up what you saw.  All the cells in all the tissues that make up you.  It has been estimated that the total number of cells in an average 70 kg male equals 3.0 x 10¹³.  Now we know that bacteria normally reside in our body, but how many?  This has actually been estimated to equal approximately 3.8 x 10¹³ cells.  So you are made up of MORE bacterial cells than “you” cells.  Think about that for a second.  These bacterial cells are an intrinsic part of us.  Some have even gone so far as to call our gut flora a separate organ or even, when combined with our immune system, another sense akin to sight, smell, or touch.
So it is clear that the gut flora should be looked upon with respect, and we have known this for some time.  When animals are raised within isolators to create germ-free animals, we can see evidence that the gut microbiota influences normal neurological development and cognition, digestion, immune response, growth, and metabolism.  So somehow changing the gut microbiota might be effective in treating disease or alleviating certain symptoms, right?  Well, that is the idea behind many sources which claim that probiotics boost immune response, improve the health of your digestive tract, relieve dermatological conditions, cure or prevent autism, treat erectile dysfunction, and so on.
But there is a huge gap between the actual science of attempting to alter the gut microbiome and these unsupported ever-growing claims.  The main issue is that the gut microbiome is extremely complicated.  There is great individual variability between the types and concentrations of bacteria that live in my gut, and those that live in your gut.  Even the Great SC has his own unique concoction of gut flora.  In fact researchers have shown that the DNA makeup of the bacteria in an individual’s intestine is like a fingerprint and is remarkably stable in each individual.  Even after a year, these researchers were able to identify participants in their study just from the analysis of their unique gut flora.
So if we all have our unique gut flora, how can we determine what strains of bacteria to use to treat a patient for whatever ailment we are trying to cure?  What dosage or concentration should we use?  By what route should we introduce our special concoction?  Maybe more importantly, is any of this safe for us?  Can probiotics actually do us harm?
This becomes even more problematic due to the under regulation of the sources of these probiotics.  When we obtain these probiotics from various sources, it’s hard to know exactly what is in these products.  Multiple studies have found discrepancies between what we see on the label and what is actually in the bottle.  In 2015, an analysis of 16 probiotic products found that only one of them matched the bacterial species reported on the label.  Furthermore, if we are trying to somehow alter our bacteria microbiota, we would optimally want live bacteria in the product, and we know that this is not always the case.

Gastrointestinal Benefits Of Probiotics

So from a gastrointestinal perspective, what are the scientifically proven health benefits of probiotics?  These appear to be few and far between.  The majority of the studies have failed to reveal any benefits in individuals that are already healthy.  There seems to be no evidence that people with normal gastrointestinal tracts benefits from these products.
What about folks that are not healthy?  Can probiotics cure a gastrointestinal disease or a condition?  
Many people with irritable bowel syndrome (IBS) come to see the Gullible Gastroenterologist every day.  Although some individual studies have shown some positive effect from probiotics on the symptoms that can be associated with IBS, there is not enough data to recommend any particular strain of bacteria for this condition, and these studies are even more problematic given that even the placebo rate for treatment of IBS averages approximately 40%.
For patients with ulcerative colitis, a disease that causes abnormal inflammation in the large intestine, some small studies have suggested some potential benefits, but combining the results of these studies together does not prove any reliable benefit.
There has been no proven benefit regarding the use of probiotics in Crohn’s disease, a condition similar to ulcerative colitis that can affect anywhere in the gastrointestinal tract.
Small controlled studies do suggest that a probiotic preparation called VSL#3 can be effective in a condition called Pouchitis.  This is a specific condition that can affect patients with ulcerative colitis that have undergone a certain surgery to treat the disease.
There is no evidence to suggest that probiotics are effective in treating celiac disease.

Probiotics And C. difficile Infection

And now we get to the intriguing topic of Clostridium difficile associated colitis.  Clostridium difficile infection typically occurs in patients who have received antibiotics for therapy for bacterial infections elsewhere in the body, pneumonia for example.  The antibiotics can alter the bacterial flora of the gut leading to overgrowth of the C. difficile bacteria.  This overgrowth leads to production of a toxin and subsequent inflammation of the colon.  This bacteria can form spores and so in some patients this condition can be very difficult to treat, resulting in multiple recurrences. 
One of the treatments for recurrent C. difficile infection involves fecal transplantation: transferring stool from a healthy patient to the affected individual. 
The Gullible Gastroenterologist had the opportunity to participate in a fecal transplantation procedure.  The stool from a related donor was prepared in a blender by an infectious disease specialist colleague of mine (this is the reason I absolutely do not attend cocktail parties hosted by that particular physician).  I performed a colonoscopy on the patient and the stool mixture was instilled into the patient’s colon. 
The patient did well with no recurrences, and fecal transplant does appear to be a promising tool in the armamentarium in treatment of recurring C. difficile infection.  That being said, there is insufficient data to support routine use of probiotics for prevention of C. difficile colitis or for treatment of active C. difficile colitis.

Why Are Probiotics Ineffective?

So there is little convincing evidence that probiotics positively effect gastrointestinal disorders.  One reason might be that bacteria from a probiotic supplement might not actually succeed in colonizing the human intestinal tract.  A recent study concluded that in some patients, probiotic strains could be identified in samples obtained from some study participants, but in others, those probiotic strains were undetectable. 
In another study, researchers looked at the fecal microbiome in patients that had received antibiotics.  Normally, a person’s microbiome will recover on its own over time after receiving antibiotics.  This usually takes about 21 days without any intervention.  Surprisingly, administering probiotics to these subjects actually delayed recovery of the microbiome to the pre-antibiotic state to greater than five months.  What does this mean?  Is this good?  Is this bad?  The answer is that we just don’t know.  Yet.

Harm From Probiotics?

Can probiotics do harm?  Although these agents are generally felt to be safe in healthy individuals, we don’t know the long term consequences.  Furthermore, probiotics should be used with caution in patients with chronic disease, are immunocompromised, or are otherwise vulnerable (such as elderly patients).

Bottom Line: More Research Needed Before Usefulness Of Probiotics Proven

So the bottom line?  Research on the fecal microbiome is certainly exciting.  This area of study definitely has the potential to be very important and likely holds the key to discovering the underlying pathophysiology to many conditions. 
But in the year 2019, we just do not have enough information to determine which preparations may be helpful, which patients should be targeted, and how. 
Although I am hopeful that someday probiotics might be an effective tool in treating some of the diseases and conditions that my patients suffer from today, I am just not gullible enough to buy into the hype associated with unsubstantiated claims regarding their usefulness until we learn much much more.
Gullibly yours,
DSL

The Gullible Gastroenterologist,
Dave Lotsoff,  lives south of Delmar in University City, Missouri  and when he’s not singing like Jim Morrison for the skeptical cardiologist’s band he practices gullible clinical gastroenterology  in St. Louis.
-ACP
N.B. Probiotics have also been promoted for lowering blood pressure and reducing risk of cardiovascular disease but the proof of benefit is similar to that for GI problems-severely lacking.
It’s far too early to recommend probiotics  for preventing or treating any chronic diseases.