The Sensitive Gut

Understanding IBS

Probiotics and Brain Fog

Rao_318A few weeks ago, on a warm midsummer evening, Dr Derek Holdsworth and I listened with a mixture of awe and interest as our one time research fellow,  Professor Satish Rao, now Chief of Gastroenterology at Medical College of Georgia, Augusta University, Augusta, GA  entertained us with changing perceptions of IBS.

America has always had a different perspective; highly evidence based and more operational.  There are notable differences.  Small intestinal bacterial overgrowth is a more popular diagnosis in the United States.  Some researchers have put the prevalence as high as 80%, but that is probably skewed by misinterpretation of the results of the lactulose hydrogen breath.  The reality is probably that about 30% of people with IBS have SIBO, still much greater than when Satish worked with us in the nineteen eighties.  ‘So what is the reason for that’, I asked.  ‘Almost certainly, proton pump inhibitors ‘, was the reply.

Proton pump inhibitors or acid blockers, omeprazole and lanzoprazole were introduced twenty years ago to treat symptoms of peptic ulcer and oesophageal reflux.  Within a year, rates of surgery for acid peptic disease had plummeted.  But blocking gastric acid secretion has some unintended consequences;  one is that it allows bacteria and fungi taken in with the food to proliferate in the stomach and invade the small intestine.  This causes fermentation of protein and carbohydrate, denatures fat and bile acid to more irritant compounds and makes the gut more leaky.  These physiological actions not only produce all the symptoms of IBS but could also, Satish explained, cause tiredness and confusion.

He described one of his patients, a woman of 51, who got ‘brain fog’ and bloating whenever she drank milk.  She had been on long term proton pump inhibitors for symptoms of reflux and was using large doses of probiotics containing lactobacillus as treatment for her alternating constipation and diarrhoea with gas and bloating.  She developed her brain fog and bloating whenever she ate.  The inference was that because of the suppression of gastric acid,  lactobacilli had colonised the small intestine in large numbers and were fermenting the lactose in milk and other carbohydrate-rich foods, which not only caused gas and bloating , but also generated excess D-lactic acid,  which caused fatigue and loss of concentration.  Treatment of SIBO and SIFO (small intestinal fungal overgrowth) with a combination of antibiotics eliminated the symptoms.

Lactic acid exists as two optical isomers.  L-lactic acid can be produced in mammalian cells by anaerobic metabolism, that can be caused briefly by strenuous exercise when demand for energy exceeds supply, but also during sepsis, diabetic ketoacidosis  and many other uncommon medical conditions.   D-lactic acid is only produced in large amounts when a diet rich in carbohydrate is fermented.  D-lactic acidosis  has been described in short bowel syndrome, after intestinal by-pass for treatment of obesity and in severe pancreatic insufficiency.  In all of these conditions,  the absorptive capacity of the small intestine is so curtailed that abnormally large amounts of carbohydrate are fermented in the colon, but it has not to my knowledge been described in patients on a high FODMAP diet containing excessive amounts of poorly absorbed fermentable carbohydrate.

Recent evidence suggests excessive production of D-lactic acid may also be produced artificially by the ingestion of megadoses of probiotics containing lactobacillus acidophilus when gastric acid secretion is suppressed by acid blockers.  Under those conditions, fermentation of milk and possibly also pulses in the stomach and the small intestine, would generate toxic amounts of D-lactic acid.

Excess D-lactate is toxic to both brain and heart cells that have a high demand for energy generated by glycolysis and oxidative phosphorylation.  In the mitochondria,  build up of D-lactate interferes with mitochondrial utilisation of two major energy products of glycolysis, L lactate and pyruvate, and reduces oxygen consumption.  In this oxygen-starved environment, cells are unable to produce adequate amounts of adenosine triphosphate (ATP), necessary for the normal   turnover of neurotransmitters and the firing of neurones.  This gives rise to symptoms of incoordination,  fatigue and confusion (brain fog).

Rehman A BC, Patel N, et al.. Brain Fogginess, Gas, Bloating and Distension: A Link Between SIBO, Probiotics and Metabolic Acidosis. Gastroenterology 2014;146:S850-S1.



7 comments on “Probiotics and Brain Fog

    July 14, 2016

    Does this work actually suggest that probiotics themselves may contribute to brain fogging or only when they are taken with acid inhibitors? I cant make out but would like to know!


    • nickwread
      July 14, 2016

      My understanding is that the acid blockers allow more of the bacteria to survive and gain access to the carbohydrate in the stomach and small intestine, generating a surge on D-lactate which affects the brain.


        July 15, 2016

        Thank you.


  2. Jen
    August 23, 2016

    My IBS got worse after probiotics following Xifaxan treatment. I now *explosively* bloat 15 minutes after eating carbs (but never meat or eggs) with constant bleching that only slightly helps the resulting pain. Even worse is the weakness that follows. Blood sugar has been tested, I am not diabetic, thyroid fine etc.

    l. I have told 3 Gastrolenterologiests who looked at me like I was saying the cia was doing experiments on me when I asked why I got this after using probiotics. One even told me I have an eating disorder. The other two had no explanation but do come back in 3 months so they can do more nothing.

    Please how can I get a local doctor to even consider this might be my problem? I am disabled and live across the country from Dr Rao so trying to get an appointment at his practice is not an option unless I win a lottery.


    • nickwread
      August 24, 2016

      From your discription, Jen, it sounds very much like the combination of Xifaxan (Rifaximin) and probiotics replaced the bacterial flora in your intestine with the probiotic species that caused more gas. I wonder if you are producing enough acid in your stomach to protect the small intestine agains invasion of new species. I would certainly come off the probiotics and while your symptoms are still severe restrict the carbs until the bloating begins to get better. Is there a local dietitian who might understand about carbohydrate fermentation and FODMAPs and could help you.
      Thank you for your communication. It will help other people. I hope your symptoms soon improve.


  3. Pingback: ‘The pain and the bloating come on as soon as I’ve eaten and then the diarrhoea starts.’ | The Sensitive Gut

  4. Pingback: Suffering from Brain Fog? What Causes It and How to Clear It

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This entry was posted on July 14, 2016 by in Brain and Gut, Microbiome, Probiotics and tagged , , , .

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