Abdominal distensionbloatingBrain fogginessD-lactic acidosisGlucose breath test

Brain fogginess, gas and bloating: a link between SIBO, probiotics and metabolic acidosis

  • 2018
  • Satish S. C. Rao, Abdul Rehman, Siegfried Yu, et al.
Why this matters for your health

Bloating and gas are very common, and some patients also report “brain fog”: confusion, poor memory, poor concentration and impaired judgment, which can be disabling (4 of 30 patients quit their jobs). D-lactic acidosis was previously known mainly in short bowel syndrome. This study describes a similar picture in people with an intact gut who were taking probiotics. It suggests that SIBO, D-lactate production and probiotic use may be linked to brain fog. It also shows that symptoms improved after stopping probiotics and giving antibiotics. The authors urge caution with indiscriminate probiotic use, but the study is observational and does not prove cause and effect.

Summary

This prospective observational study at a tertiary center (Medical College of Georgia, Augusta University, USA) enrolled consecutive adults with unexplained gas, bloating and distension. Thirty patients had brain fogginess (BF) and 8 did not. All had normal endoscopy, colonoscopy, imaging and blood tests. SIBO was assessed by glucose breath test and duodenal aspirate culture. D-lactic acidosis was assessed by urinary D-lactate and blood L-lactate after a glucose challenge, and gut transit was also measured. Every BF patient was taking probiotics. SIBO and D-lactic acidosis were significantly more common in the BF group, and BF was reproduced during the breath test in about two-thirds of patients. After stopping probiotics and receiving antibiotics (or dietary advice if no SIBO was found), most patients improved and most reported BF resolved. The authors call it a syndrome “possibly related” to probiotics, SIBO and D-lactic acidosis.

Key findings

  • 42 patients were evaluated. After exclusions, 30 with BF (19 women, 11 men, mean age 52) and 8 without BF (5 women, 3 men, mean age 49) were analyzed.
  • All 30 BF patients took probiotics (3 months to 3 years), and 11 (36.7%) also ate cultured yogurt daily. Only 1 of 8 non-BF patients took probiotics.
  • GI symptoms (pain, bloating, distension, gas) were equally severe in both groups. BF symptoms lasted from 30 minutes to several hours and were often after meals. 28/30 (94%) reported post-meal fatigue or weakness.
  • SIBO (positive glucose breath test and/or duodenal culture) was found in 19/30 (63.3%) BF patients versus 25% of non-BF patients (p = 0.05). Culture alone was positive in 14 (46.7%), and the breath test alone in 11 (36.6%).
  • D-lactic acidosis was found in 23/30 (76.7%) BF patients versus 25% of non-BF patients (p = 0.006). Concurrent L-lactic acidosis occurred in 9/30 (30%). All 19 BF patients with SIBO had D-lactic acidosis.
  • The patient’s usual BF was reproduced during the breath test in 20/30 (66%), and all of them had SIBO by breath test or culture.
  • Abnormal gut transit occurred in 10/30 (33%) BF patients, versus 2 to 3 of 8 in the non-BF group. The difference was not significant, so dysmotility alone does not seem to explain BF. All 10 BF patients with dysmotility had SIBO and lactic acidosis.
  • 10/13 (78%) PPI users and 4/7 opioid users had D-lactic acidosis, so these drugs may predispose to SIBO.
  • Kidney and liver function were normal. Ammonia was mildly raised during the test in 9/30 (30%).
  • Cultures grew many bacteria, including Streptococcus, Staphylococcus and Neisseria, plus Lactobacillus and Prevotella in some patients. The authors note that these bacteria are often resistant to routine antibiotics.
  • After stopping probiotics and receiving antibiotics (N = 23), or stopping probiotics and yogurt only (N = 7), 70% reported significant symptom improvement (global VAS 2.0 to 7.4; p = 0.005). Complete BF resolution was reported by 85%. Abdominal pain, cramping, bloating, fullness and distension improved significantly (for example bloating 6.5 to 4.08).
  • The 4 non-BF patients with SIBO or D-lactic acidosis also improved on antibiotics, to a similar degree.
  • Limitations: observational design, no standard definition of BF (≥2 symptoms were used), no culture of the distal small bowel, no retesting after treatment, and it is unclear whether SIBO existed before probiotics. Only one non-BF patient took probiotics, so the probiotic link is not fully tested. The sample is small and from one center.
  • Some numbers in the PDF are inconsistent. The abstract gives SIBO as 68% vs 28% and improvement as 23/30 (77%), while the results give 63.3% vs 25%, 70% improvement and 85% BF resolution. Table 1B appears to show three non-BF patients above the D-lactate cutoff, while the text says two. Check the original before quoting exact figures.
  • Dr. Rao reports consulting for several pharmaceutical companies (none related to this report). No financial support was reported.

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Citation

Rao SSC, Rehman A, Yu S, Martinez de Andino N. Brain fogginess, gas and bloating: a link between SIBO, probiotics and metabolic acidosis. Clinical and Translational Gastroenterology. 2018;9:162. doi:10.1038/s41424-018-0030-7

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