The study, carried out by UCLA researchers, found that brain function changed among healthy women who consumed probiotics in yogurt.
Brain function changed among the women while in a resting state as well as during an emotion-recognition task.
They found that the bacterial environment in the gut can affect brain activity.
The researchers said that this finding has important implications for future dietary or drug interventions to improve brain function.
Dr. Kirsten Tillisch, an associate professor of medicine at UCLA's David Geffen School of Medicine and lead author of the study, 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. 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."
stress can often be the cause of gastrointestinal problems.
The authors say their study proves what has been suspected for some time.
Tillisch added that "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."
A total of 36 women between the ages of 18 and 55 were included in the study. They were split into three different groups:
- Group one ate a yogurt containing a mix of several probiotics twice a day for four weeks
- Group two consumed a diary product that contained no probiotics
- Group three ate no product at all
The emotion-recognition task involved making the women look at pictures of angry or frightened faces and matching them to other faces with the same expressions. This was done in order to measure the affective and cognitive brain regions' response to visual stimulus.
They found that during the emotional reactivity task, those who consumed the probiotic yogurt experienced less activity in both the insula and the somatosensory cortex - which processes internal body sensations.
In addition, women who consumed the probiotic yogurt had decreased activity in emotion-, cognition- and sensory-related areas of the brain compared to those in the two other groups.
In a resting state, women consuming probiotics had shown more connectivity between an important brainstem region called the periaqueductal grey and areas of the prefrontal cortex responsible for cognition.
Tillisch said he was surprised to see that brain effects occurred in various different regions, including those that have nothing to do with emotion, such as sensory processing.
Dr. Emeran Mayer, a professor of medicine, physiology and psychiatry at the David Geffen School of Medicine at UCLA and the study's senior author, said that the fact that signals sent from the intestine to the brain can be influenced by dietary change, will hopefully drive further research on digestive and mental 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. Now we know that this has an effect not only on the metabolism but also affects brain function."
The researchers are now focusing on finding the chemicals that the gut produces which send signals to the brain.
In addition, they want to find out whether gastrointestinal symptoms including bloating, abdominal pain and altered bowel movements correlate to variations in brain response.
Future research will look into whether probiotics have any effect on mood symptoms and anxiety.
The researchers hope that in the future they will be able to manipulate intestinal content to treat brain related diseases such as Alzheimer's or Parkinson's.
Benefits of ProbioticsAccording to a recent study published in the British Journal of Sports Medicine, professional long distance runners who ingested the probiotic Lactobacillus had shorter and less severe spells of respiratory illness than those who ingested a placebo.
Scientists at Michigan State University reported in the Journal of Cellular Physiology, that a natural probiotic supplement can help male mice produce healthier bones.
Probiotic bacteria have the potential to alter brain neurochemistry and treat anxiety and depression-related disorders, according to research published in the prestigious international journal Proceedings of the National Academy of Sciences (PNAS).