Probiotic yogurt may change brain function

Eating probiotic yogurt can not only alter your gut bacteria for the better, it may also change your brain function, scientists say.

University of California, Los Angeles researchers now have the first evidence that bacteria ingested in food can affect brain function in humans.

In a small study of healthy women, between the ages of 18 and 55, researchers found that women who regularly consumed beneficial bacteria known as probiotics through yogurt showed altered brain function, both while in a resting state and in response to an emotion-recognition task.

The discovery that changing the bacterial environment, or microbiota, in the gut can affect the brain carries significant implications for future research that could point the way toward dietary or drug interventions to improve brain function, the researchers said.

"Many of us have a container of yogurt in our refrigerator that we may eat for enjoyment, for calcium or because we think it might help our health in other ways," said Dr Kirsten Tillisch, an associate professor of medicine at UCLA's David Geffen School of Medicine and lead author of the study.

"Our findings indicate that some of the contents of yogurt may actually change the way our brain responds to the environment. When we consider the implications of this work, the old sayings 'you are what you eat' and 'gut feelings' take on new meaning," Tillisch said.

Researchers divided the women into three groups: one group ate a specific yogurt containing a mix of several probiotics twice a day for four weeks; another group consumed a dairy product that looked and tasted like yogurt but had no probiotics; and third group ate no product at all.

They found that, compared with women who didn't consume the probiotic yogurt, those who did showed a decrease in activity in both the insula - which processes and integrates internal body sensations, like those from the gut - and the somatosensory cortex during the emotional reactivity task.

Further, in response to the task, these women had a decrease in the engagement of a widespread network in the brain that includes emotion-, cognition- and sensory-related areas. The women in the other two groups showed a stable or increased activity in this network.

During the resting brain scan, the women consuming probiotics showed greater connectivity between a key brainstem region known as the periaqueductal grey and cognition-associated areas of the prefrontal cortex.

The women who ate no product at all, on the other hand, showed greater connectivity of the periaqueductal grey to emotion- and sensation-related regions, while the group consuming the non-probiotic dairy product showed results in between.

The researchers were surprised to find that the brain effects could be seen in many areas, including those involved in sensory processing and not merely those associated with emotion, Tillisch said.

The study will be published in the journal Gastroenterology.