Dietary changes to the bacteria living in our guts could have an impact on brain functioning, a new study suggests.
Researchers at the University of California, Los Angeles, found that regularly eating yogurt with probiotics, which contain "good" bacteria, seems to affect brain functioning in women. They said the proof-of-concept study shows it is possible to impact brain functioning by altering gut bacteria through diet.
The study, published in the journal Gastroenterology, was funded by Danone Research, which is the research arm of Danone, a company that produces yogurt and other dairy products. Some of the study researchers are Danone employees, but they had no role in the interpretation or analysis of results.
Researchers noted that past studies have shown a gut-brain connection in terms of the brain sending signals to the gut. But this new study shows that the gut could also send signals to the brain.
"This study is unique because it is the first to show an interaction between a probiotic and the brain in humans," study researcher Dr. Kirsten Tillisch, M.D., an associate professor at the Oppenheimer Family Center for Neurobiology of Stress at the UCLA David Geffen School of Medicine, told Medscape Medical News. "We can't say whether the effects are beneficial; that will take larger studies with more complex designs. One of the areas this will move to is study of disease groups like irritable bowel syndrome and anxiety."
The study included 36 women between ages 18 and 55, who were split up into three groups and assigned an eating regimen for four weeks. One group ate yogurt with probiotics two times a day, the second group ate a yogurt-like product that didn't have probiotics, and the third group ate neither. Researchers had the study participants undergo imaging scans before and after the four-week period, as they completed a test where they had to match faces showing a certain emotion with other faces showing the same emotion.
Researchers found that that women who consumed the probiotics had changes in activity and engagement of certain brain regions. For instance, the insula brain region (involved in processing sensations that come from within the body) had decreased activity, and there was increased connectivity between parts of the prefrontal cortex involved in cognition and a part of the brainstem, called the periaqueductal grey.
"Four-week intake of an FMPP [fermented milk product with probiotic] by healthy women affected activity of brain regions that control central processing of emotion and sensation," the researchers concluded in the study.
"There are studies showing that what we eat can alter the composition and products of the gut flora -- in particular, that people with high-vegetable, fiber-based diets have a different composition of their microbiota, or gut environment, than people who eat the more typical Western diet that is high in fat and carbohydrates," study researcher Dr. Emeran Mayer, a professor of medicine at the university, said in a statement. "Now we know that this has an effect not only on the metabolism but also affects brain function."
According to the American Psychological Association, past studies in animals have also shown that altering gut bacteria in animals can produce more anxious or bold characteristics. In a 2011 study in the Proceedings of the National Academy of Sciences, researchers found that probiotics seemed to blunt physiological stress responses of mice, and also lowered their levels of stress hormone, compared with mice not fed probiotics.