August 10, 2018
Probiotics—live bacteria and yeasts that purportedly are good for your digestive system and immune response—have become a multi-billion-dollar business. In 2017, the global market for pills, powders, and yogurts packed with probiotics was about $46 billion, according to Statista. By 2022, experts forecast that the “digestive health, immunity, and probiotics” category of consumer products will exceed $64 billion, according to a report in the August issue of Psychology Today.
Marketers claim that they will optimize our overall health by increasing the “good” bacteria in our guts. However, researchers increasingly are finding that, although these products are generally safe, “too much of a good thing” can have unexpected repercussions.
Specifically, findings of a study conducted by researchers at the Medical College of Georgia (published in June by the journal, Clinical and Translational Gastroenterology) indicate that 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.
Out of 38 patients who agreed to participate in the study, 30 reported problems such as confusion and difficulty concentrating, in addition to gas and bloating. All subjects were taking probiotics—some of them, 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 lead author Dr. Satish S.C. Rao, director of Neurogastroenterology/Motility and the Digestive Health Clinical Research Center at the college.
Indeed, D-lactic acid is known to be temporarily toxic to brain cells, interfering with cognition, thinking, and sense of time. They found some patients had two to three times the normal amount of D-lactic acid in their blood.
According to the authors, “Brain Fogginess (BF) describes a constellation of symptoms [comprising] mental confusion, impaired judgment, poor short-term memory, and difficulty with concentration, which is often transient and disabling.” Some study participants said that their brain fogginess—which lasted from a half hour to many hours after eating—had been so severe that they had to quit their jobs.
The published report 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. .” Notably, the researchers found that over two-thirds of patients with brain fogginess who were taking probiotics demonstrated D-lactic acidosis and a higher prevalence of small intestine bacterial overgrowth.
“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.
In some people, for reasons that are not understood, probiotics appear to cause bacterium lactobacillus to go into a feeding frenzy. This leads to the rapid fermentation of sugars, which results in the production of belly-bloating methane and hydrogen gas. According to the researchers, the excessive amounts of D-lactic acid being produced in the small intestine is absorbed into the blood and can travel to the brain—temporarily interfering with cognitive functions..
Although this study is a first step towards understanding a possible link between probiotic use and brain fogginess, more research is needed. The authors acknowledge that this pioneering research has some significant shortcomings, including a small sample size.
Many individuals randomly self prescribe over-the-counter probiotics and eat these chewables like candy. Although probiotics can be beneficial in some situations, the investigators warn consumers to avoid excessive and indiscriminate use of probiotic supplements. “Probiotics should be treated as a drug, not as a food supplement,” Rao concluded.
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