Probiotic use can result in a significant accumulation of bacteria in the small intestine that can result in disorienting brain fogginess as well as rapid, significant belly bloating, a team of US researchers has reported.
In a published study of 38 patients, the 30 who reported problems like confusion and difficulty concentrating, in addition to their gas and bloating, were all taking probiotics, some several varieties.
When investigators looked further, they found large colonies of bacteria breeding in the patients’ small intestines, and high levels of D-lactic acid being produced by the bacteria lactobacillus’ fermentation of sugars in their food, says Dr Satish S C Rao, director of neurogastroenterology/motility and the Digestive Health Clinical Research Center at the Medical College of Georgia at Augusta University.
D-lactic acid is known to be temporarily toxic to brain cells, interfering with cognition, thinking and sense of time.
The researchers found some patients had two to three times the normal amount of D-lactic acid in their blood. Some said their brain fogginess – which lasted from a half hour to many hours after eating – was so severe that they had to quit their jobs.
The report in the journal Clinical and Translational Gastroenterology appears to be 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, Rao says.
“What we now know is that probiotic bacteria have the unique capacity to break down sugar and produce D-lactic acid. So if you inadvertently colonize your small bowel with probiotic bacteria, then you have set the stage for potentially developing lactic acidosis and brain fogginess,” Rao says.
While acknowledging the benefits of probiotics in specific scenarios – like helping a patient restore his gut bacteria after taking antibiotics – the researchers advised caution against its excessive and indiscriminate use.
“Probiotics should be treated as a drug, not as a food supplement”
“Probiotics should be treated as a drug, not as a food supplement,” Rao says, noting that many individuals self-prescribe the live bacteria, which are considered good for digestion and overall health.
Other studies have implicated probiotics in the production of D-lactic acid – and brain fogginess – in patients with a short bowel so their small intestine does not function properly, and in newborns fed formula containing the popular product. Short bowel syndrome results in a lot of undigested carbohydrates that are known to cause small intestinal bacterial overgrowth, or SIBO, and the high levels of D-lactic acid. Severe liver and kidney problems can produce similar problems.
But whether there was also a connection when the gut is intact was an unknown. “This is the first inroad,” says Rao.
All patients experiencing brain fogginess took probiotics and SIBO was more common in the brain fogginess group as well, 68 percent compared to 28 percent, respectively. Patients with brain fogginess also had a higher prevalence of D-lactic acidosis, 77 versus 25 percent, respectively.
When brain-foggy patients stopped taking probiotics and took a course of antibiotics, their brain fogginess resolved.
Normally there is not much D-lactic acid made in the small intestines, but probiotic use appears to change that, says the Augusta team. SIBO, which was present in most with brain fogginess, can cause bacteria to go into a feeding frenzy that ferments sugars resulting in production of uncomfortable things like hydrogen gas and methane that explain the bloating.
Probiotics added to that feeding frenzy the bacterium lactobacillus, which produces D-lactic acid as it breaks down sugars, The acid get absorbed in the blood and can reach the brain.
All those with brain fogginess, SIBO and/or D-lactic acidosis, were given antibiotics that targeted their bacterial population and asked to discontinue probiotics. Those without SIBO were asked to halt probiotics and stop eating yogurt, which is considered one of the best sources of probiotics. Those with SIBO and D-lactic acidosis but no brain fogginess also took antibiotics.
Following treatment, 70 percent of patients reported significant improvement in their symptoms and 85 percent said their brain fogginess was gone. Those without brain fogginess but with SIBO and high levels of D-lactic acid reported significant improvement in symptoms like bloating and cramping within three months.
Probiotic use may be particularly problematic for patients who have known problems with motility, as well as those taking opioids and proton pump inhibitors, which reduce stomach acid secretion and so the natural destruction of excessive bacteria.
Probiotics are supposed to work in the colon and not the small intestines or stomach, Rao says, so motility issues can result in problems with probiotic bacteria reaching the proper place. A wide variety of problems, from conditions like diabetes to drugs like antidepressants and minerals like iron, can slow movement and increase the possibility that probiotics will remain too long in the upper gut where they can cause harm, he says.
Probiotics definitely can help, for example, people who have gastroenteritis, or stomach flu, or are left with diarrhea and other problems after antibiotics wipe out their natural gut bacteria, Rao says.
“In those situations, we want to build up their bacterial flora so probiotics are ideal,” he says. Next steps include additional studies in which the investigators better quantify and characterize the brain fogginess reported by patients and following patients for longer periods to ensure their problems remain resolved. Some patients in the current study required a couple of rounds of antibiotics, Rao notes.
Rao said that consumption of sources of probiotics – including yogurt, sauerkraut, kimchi, kefir and dark chocolate – should continue to be encouraged as they contained safe amounts of bacteria.
Photo: Small intestinal bacterial overgrowth, or SIBO. Photo by Eric Erbe, digital colorization by Christopher Pooley.