Probiotics, Crappy Science and The Right to Choose

A month or two ago, a friend wrote to me suggesting that I address the question, “are probiotics always good for you?”  I promised I would – and fully intended to keep that promise soon – but one of the big news headlines this week made soon into now.

By the way, sorry in advance.  This is one long post.  The more I wrote, the more I found I had to write!  Please bear with me.

First, the big headline:  a study[i] of 30 patients at the Digestive Health Clinical Research Center at the Medical College of Georgia at Augusta University, who came in reporting issues with confusion, difficulty concentrating, gas and bloating, abdominal pain, found that all were taking probiotics and all were suffering from SIBO (small intestine bacterial overgrowth).  While bacteria are found throughout the digestive tract, the vast majority are in the large intestine. When there’s an overgrowth in the small intestine, which can be caused by a variety of factors (anything that affects gut motility like diabetes, the use of proton pump inhibitors, obesity, etc.), gastrointestinal (GI) symptoms – and mental ones – can be the result.

D-lactic acid is one byproduct of bacteria and in cases of SIBO, where there may be some inflammation in the intestinal wall leading to leaky gut, these byproducts can get into the blood stream and cause intoxication –  that is, they are literally toxic to brain cells. The patient may experience a variety of “mental” symptoms including profound brain fog. These 30 patients, who had the GI symptoms and brain fog, had 2-3X the normal amount of D-lactic acid in their blood.

The patients were taken off the probiotics, put onto antibiotics, and mostly recovered.

Now here is where I let off a little steam.

Firstly,  Dr. Satish Rao, the lead author of the paper, claims that this is the  “…first time the connection has been made between brain fogginess, bacterial overgrowth in the small intestine, high levels of D-lactic acid in the gut and probiotic use…”[ii]  Two things to keep in mind though:

  1. In actuality, he has not in any way proven that these symptoms were the result of probiotics.


  1. Remember that the link between high levels of D-lactic acid in the gut, bacterial overgrowth, and brain fog has been known for decades. In fact, Elaine Gottschall said it 25 years ago, in her book, Breaking the Vicious Cycle:

“The presence of undigested and unabsorbed carbohydrates within the small intestine can encourage microbes from the colon to make up residence in the small intestine and to continue to multiply.  This, in turn, may lead to the formation of products, in addition to gas, which injure the small intestine.  Examples are lactic, acetic, and other acids which are short-chain organic acids resulting from the fermentative process.  In addition to the damage to the intestine, there is a growing body of scientific evidence that lactic acid formed from fermentation in the intestine causes abnormal brain function and behavior.”[iii]

Secondly, Dr. Rao goes on to say, “Probiotics should be treated as a drug, not as a food supplement…”

Uh oh.  (You think there’s any chance of me getting feisty shortly?!)  🙂

I’ll come back to that statement later.  Firstly, let’s look at this paper in a little more detail:

  1. Flat out, the paper states, “Whether there is a link between abdominal bloating, distention, gas, D-lactic acidosis, and small intestinal bacterial overgrowth (SIBO), and probiotic usage is not known.”
  2. There is NO mention of when or why the patients began to use probiotics. Therefore, it is equally as likely as not that they did so because THEY WERE ALREADY EXPERIENCING GI AND/OR BRAIN FOG SYMPTOMS.
  3. An association is not proof of causation. That is, just because I am cranky right now, and writing about something that is annoying, does not PROVE that my crankiness is caused by this annoying thing.  I could be cranky because I’m tired, I’m hungry, my dog vomited on the carpet, etc.  To draw a conclusion – “probiotics caused these patients to have SIBO and brain fog” – simply because they were taking probiotics and experience these symptoms would be false logic.
  4. The paper actually says this: “Here, the BF [brain fog] was likely induced by the production of toxic metabolites such as D-lactic acid in the small intestine from bacterial fermentation of carbohydrate substrates. The use of prolonged or excessive probiotics and/or cultured yogurt further contributed to the small intestinal colonization by lactobacilli and other bacteria.”  That is – the probiotics may have CONTRIBUTED to an already existing issue.   The paper does not actually though provide scientific proof of that, so that’s a hell of a leap.  And leads to the question of course, how many people have come to this medical center with SIBO and brain fog are NOT taking probiotics?
  5. Remember that there are trillions (it’s currently estimated about 100 trillion) – of bacteria in the gut. The average probiotic has maybe 10 billion organisms.  So my very reasonable question is: is it actually likely that this proverbial drop in the ocean has meaningfully contributed to these patients’ SIBO?
  6. And finally, to answer my friend’s question about when should they not be used, the paper states, “Probiotics are considered to be safe and beneficial including improvement in gut barrier function and gut transit. Although a meta-analysis of 57 studies indicated that probiotics are safe, caution against its use has been recommended in subjects who are immunosuppressed, pregnant, and with structural heart lesions, acute abdomen, neutropenia, chemotherapy and radiotherapy.”

Just a few weeks ago, a report came out in the Annals of internal Medicine that pointed out that few studies done on probiotics reported side effects or, if they did, they did so insufficiently.[iv]  These French researchers, from Paris Descartes University, note that of the 384 clinical trials they reviewed, 37% did not report safety results, and only 28% presented harm-related data.

Now, let’s look objectively at what that means:

  1. They reviewed 384 trials. That is not the total number of clinical trials DONE – it is simply the ones they reviewed.
  2. If only 37% of them did not report safety results, 63% DID report safety results. And 72% DID report harm-related data.   So the vast majority of studies reviewed provided safety data.
  3. Please be aware that in some or all of these trials, safety and tolerability data may not have been reported because there were no adverse effects. (Yes, it would have been nice if the authors would have noted that.  But the lack of reported data does not prove that there was data to report.)

As one US doctor, from Baylor College of Medicine, noted, “The French researchers ‘did not find evidence suggesting that these products are unsafe…Rather, they highlight the need to report safety data more rigorously in the future.’”

Fair enough.

Now back to Dr. Rao’s statement suggesting we start to regulate probiotics as pharmaceutical drugs. My opinion for what it’s worth….

You must be kidding me.  Just what we need all need – even more regulation.  What ever happened to good, old fashioned, common sense?  If you are healthy, and choose to take probiotics, they may or may not help you but the choice of where to spend your money is still yours.  If you are sick, running supplements by your doctor is already a pretty damn good idea. If you don’t, then that’s on you.  There is such a thing (or at least there should be a thing) as personal responsibility.  Do we or do we not believe in personal freedom any more?

Maybe some people love the idea of living in a nanny state.  Me personally – I’ll take my chances and keep the right to choose, thank you.


[i] Satish S. C. Rao, Abdul Rehman, Siegfried Yu, Nicole Martinez de Andino. Brain fogginess, gas and bloating: a link between SIBO, probiotics and metabolic acidosis. Clinical and Translational Gastroenterology, 2018; 9 (6) DOI: 10.1038/s41424-018-0030-7


[iii] Gottschal, Elaine.  Breaking the Vicious Cycle.  2000. Kirkton Press:Baltimore, Ontario.

[iv] Swaminath, A, Novak, J, Preidis, G.  Annals of Internal Medicine, July 16, 2018.

One Comment on “Probiotics, Crappy Science and The Right to Choose

  1. Pingback: More on Probiotics and Crappy Science or…An LOL! – THE BIOME BUZZ

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