May 29, 2013
Probiotics Found In Yogurt Affects Brain Function In Women
April Flowers for redOrbit.com - Your Universe Online
The first evidence that bacteria ingested in food can affect brain function in humans has been found by a group of researchers from the Gail and Gerald Oppenheimer Family Center for Neurobiology of Stress (CNS) and the Ahmanson Lovelace Brain Mapping Center, both of which are research arms of the UCLA.The scientists conducted an early proof-of-concept study of healthy women, finding that women who regularly consumed beneficial bacteria known as probiotics, found in yogurt, showed altered brain function. This alteration showed both while in a resting state and in response to an emotion-recognition task.
The research team says that the discovery that changing the microbiota, or bacterial environment, of the gut can affect the brain carries significant implications for future research that could highlight dietary or drug interventions to improve brain function. The results of their study were published in a recent issue of Gastroenterology.
"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 Kirsten Tillisch, MD, an associate professor of medicine at UCLA's David Geffen School of Medicine. "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."
Scientists have long known that the brain sends signals to the gut. This is why stress and other emotions can contribute to gastrointestinal symptoms. Until now, researchers have suspected, but been unable to prove except in animal models, that signals travel the opposite way as well.
"Time and time again, we hear from patients that they never felt depressed or anxious until they started experiencing problems with their gut," Tillisch said in a statement. "Our study shows that the gut—brain connection is a two-way street."
The study sample was small; 36 women between the ages of 18 and 55 were divided into three groups. One group ate a specific yogurt containing a mix of several probiotics twice a day for four weeks. The second group consumed a dairy product that looked and tasted like the yogurt, but contained no probiotics. The final group ate no product at all.
The team conducted functional magnetic resonance imaging (fMRI) scans before and after the four-week study period, looking at the women´s brains in a state of rest and in response to an emotion-recognition task.
The task, which involved looking at a series of pictures of people with angry or frightened faces, and matching them to other faces showing the same emotion, is designed to measure the engagement of affective and cognitive brain regions in response to visual stimulus. The team chose this particular test because previous research in animals had linked changes in gut flora to changes in affective behaviors.
The women who consumed the probiotic yogurt 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. This decrease was not noted in the women who did not consume the yogurt.
The women who ate the probiotics also had a decrease in the engagement of a widespread network in the brain that includes emotion-, cognition- and sensory-related areas. Both of the other groups showed a stable or increased activity in this network.
The probiotics group showed greater connectivity between a key brainstem region known as the periaqueductal grey and cognition-associated areas of the prefrontal cortex during the resting brain scan. The group that ate no product at all exhibited greater connectivity of the periaqueductal grey to emotion- and sensation-related regions. The group that ate the non-probiotic dairy product demonstrated results in between the other two groups.
The results surprised the research team, who didn´t expect 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.
Emeran Mayer, MD, a professor of medicine, physiology and psychiatry at the David Geffen School of Medicine at UCLA, said that the knowledge that signals are sent from the intestine to the brain and that these signals can be modulated by dietary changes is likely to lead to an expansion of research targeted at finding new techniques to prevent or treat digestive, mental and neurological disorders.
"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," Mayer said. "Now we know that this has an effect not only on the metabolism but also affects brain function."
The team is seeking to pinpoint particular chemicals produced by gut bacteria that may be triggering signals to the brain. They are also planning future research into whether people with gastrointestinal symptoms such as bloating, abdominal pain and altered bowel movements have improvements in their digestive symptoms which correlate with changes in brain response.
Other teams, according to Mayer, are studying the potential benefits of certain probiotics in yogurts on mood symptoms such as anxiety.
The current study raises the question of whether repeated courses of antibiotics can affect the brain, as some studies have speculated. Extensively used in neonatal intensive care units and in childhood respiratory tract infections, antibiotics might have long-term consequences on brain development as well.
Researchers may find ways to manipulate the intestinal contents to treat chronic pain conditions or other brain related diseases, including, potentially, Parkinson's disease, Alzheimer's disease and autism as the complexity of the gut flora and its effect on the brain becomes better understood.