Probiotic gut effects may alter brain activity

Early results show that eating a probiotic fermented product may have an effect on gut flora that actually leads to changes in the brain, researchers found. A double-blind, controlled, parallel study of healthy female patients found that those who consumed probiotic-infused yogurt had a muted response from brain regions involved in emotional arousal and stressful gut signaling, according to data from Kirsten Tillisch, MD, of the University of California, Los Angeles, and colleagues reported at Digestive Disease Week. "By changing the environment in the gut, we can actually change what happens in the brain," Tillisch said in an interview with MedPage Today, cautioning, however, that the work is still in early stages. Preclinical studies have demonstrated that changes in gut microbiota can alter central signaling mechanisms and emotional behavior. But these changes have never been shown in humans after modulation of gut microbiota with probiotics or antibiotics, the authors explained. They randomized 45 women, ages 18 to 50, without psychiatric or medical illnesses to one of three intervention groups -- no product, a control non-fermented yogurt, or probiotic yogurt that contained B. lactis CNCM I-2494, yogurt symbiosis L. bulgaricus, S. thermophilus, and L. lactis. Patients in the control and probiotic groups consumed 125 g of product twice daily over the 4-week intervention. They completed an emotional reactivity task after being shown negative emotional faces between viewing shapes as a control, which was intended to elicit a blood oxygen level-dependent (BOLD) response indicating brain activity. Patients were scanned with function MRI (fMRI) before and after the task to measure BOLD response. The probiotic group showed a muted BOLD response in brain areas involved in processing and modulation of gastrointestinal sensation compared with the control (P=0.002 for familywise error [FWE]) and no product groups (P=0.016 for FWE), Tillisch said. But no BOLD differences were seen in the cingulate, prefrontal cortex (PFC), or amygdala. The probiotic dairy group did show decreased connectivity of an amygdala-centered network with the insula, dorsal striatum, and lateral PFC. Thus, changing the balance of bacteria in the gut through chronic probiotic consumption may alter emotional response to negative stimuli, Tillish said during a press briefing. However, she clarified that the study was a very early step in establishing a link between emotional affect and probiotic alteration of gut flora. John Petrini, MD, from the Sansum Clinic in Santa Barbara, Calif., told MedPage Today that he "found the data interesting but preliminary. Certainly the interaction between the gut bacteria and the human system is a great source of interest, but it is hard to draw definitive conclusions from just one study." He pointed out that the study was sponsored by a dairy products producer, so "I doubt that it will be long before the claims of extraordinary benefit from eating yogurt will be on the air and in print." Tillisch said that future research would apply the initial research to patients with gastrointestinal disorders, such as irritable bowel syndrome. Future research also needs to explore the mechanisms of action, looking at changes in the gut during the period of consumption, and then comparing the results in human with results from earlier probiotic studies in animal models. Primary source: Digestive Disease Week