….Study finds probiotics affect areas of the brain related to emotions and reasoning
Probiotics found in natural yogurt could help boost a person’s mood because they affect brain function, according to new research.
Previous studies had shown that beneficial bacteria affected the brains of rats but no research has confirmed that the same occurred in human brains.
The study found that those who ate probiotic yoghurt twice daily for a month showed altered brain function, both in resting brain activity and in response to an ’emotional attention task’, which was designed to monitor how the brain responded to certain emotions.
It has been known for some time that symbiotic gut bacteria, the complex ecosystem of microorganisms that live in the human digestive system, promote health by boosting immunity, aiding digestion, as well as maintain a healthy weight and blood pressure.
It has also been known that the brain sends signals to the gut, which is why stress and other emotions can contribute to gastrointestinal symptoms. This study shows that signals travel the opposite way as well.
‘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,’ said Dr. Kirsten Tillisch of UCLA’s School of Medicine, who led the study.
‘Time and time again we hear from patients that they never felt depressed or anxious until they started experiencing problems with their gut.
‘Our study shows that the gut-brain connection is a two-way street,’ she added.
Tillisch’s team recruited 36 women of a healthy weight aged between 18 and 53.
They were assigned to one of three groups. One group ate a yogurt with live bacterial cultures containing probiotic strains such as Bifidobacterium animalis, Streptococcus thermophiles, and Lactobacillus bulgaricus twice a day for one month.
Another ate a dairy product which contained no living bacteria, and another was given no dairy products at all.
Before and after the one-month study period, the researchers conducted functional magnetic resonance imaging (fMRI) brain scans on the women.
In each session, they started with a five-minute scan of the brain at rest, while the women lay still with their eyes closed.
Afterwards, the participants were asked to perform an ‘emotional faces attention task’, in which their brains were scanned while they matched a series of
angry or fearful faces on a computer screen to other faces that appeared.
The results showed that during the emotional task, women who ate the probiotic yogurt had reduced activity in a brain network that included the somatosensory cortex – which receives sensory information – and the insula, a brain region that integrates sensory feedback from internal parts of the body including the gut.
They also had reduced activity in the prefrontal cortex, precuneus, and basal ganglia, which handle aspects of cognition and emotion.
The women who ate non-probiotic yogurt or no dairy showed either no change, or an increase of activity in this network over time.
In the resting state, the brain scans of the women who ate probiotic yogurt showed stronger connectivity in a neural network which connects the periaqueductal grey (PAG) &mdash a region of the brainstem involved in responding to pain and emotional stimuli — to areas of the prefrontal cortex related to aspects of cognition like decision-making.
The women who ate no dairy, however, had stronger connectivity of the PAG to sensory and emotion-related parts of the brain, like the insula, somatosensory cortex, and amygdala.
The mechanisms behind these changes are unclear, wrote the researchers, but it’s clear that gut bacteria send molecular signals to the brain that can change over time.
Dr. Emeran Mayer, who also worked on the study, said that what we eat alters the way our gut bacteria breaks down food.
While diets high in vegetables and fibre promote healthy gut bacteria, the typical Western diet full of fats, sugars, and carbohydrates, can do the opposite.
The research team hopes to identify which signals from the gut bacteria lead to a shift in brain activity.
People with digestive conditions linked to gut dysbiosis (an imbalances in gut bacteria) such as irritable bowel syndrome, might show such shifts in brain
response if they are treated with probiotics.
Dr Mayer also suggested that specific probiotic strains in yogurt could have health benefits such as relieving anxiety, stress, and other mood symptoms over time.
As tests to analyse bacteria growth in individuals become more readily available, it will become easier to see how someone’s gut bacteria makeup influences factors like brain development, stress, and pain sensitivity.
It is possible that changing the composition of gut bacteria could lead to treatments for chronic pain disorders, he said, as well as symptoms of brain conditions like autism, Parkinson’s, and Alzheimer’s disease.