The food you eat can directly affect your brain function, according to a new study conducted by researchers from the University of California-Los Angeles and published in the journal Gastroenterology. The study found that women who ate probiotic-rich yogurt showed changes in brain activity, connectivity and engagement.
“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,” lead author Kirsten Tillisch said. “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.”
Widespread brain changes
It is well established that emotional and cognitive states, such as stress, can cause changes in the operation of the gut, but research is just beginning to emerge showing that the gut can affect the brain as well. Some animal studies, for example, have linked changes in gut flora to changes in behaviors related to emotion.
“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. “Our study shows that the gut-brain connection is a two-way street.”
The researchers randomly assigned 36 women between the ages of 18 and 55 either to consume a probiotic-rich yogurt mix, a dairy product with the look and taste of yogurt but with no probiotics, or no product.
Probiotics are microorganisms that live in the gut and have beneficial health effects.
At the study’s start and after four weeks of the intervention, all participants underwent a functional magnetic resonance imaging (fMRI) scan, both in a state of rest and during an emotional stimulus test. The test consisted of looking at pictures of angry or frightened faces and matching them with other faces demonstrating the same emotion.
The researchers found that compared with the placebo group, women who ate probiotics showed decreases in activity of the brain regions known as the insula and the somatosensory cortex; decreases in engagement of a widespread network associated with emotion, cognition and sensation; and greater connectivity between the periaqueductal grey and several areas in the prefrontal cortex associated with cognition. The researchers expressed surprise that changes were seen in such diverse regions of the brain.
Changes were seen in both resting and emotional stimulus states, although not the same ones.
New research opportunities
“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,” senior author Emeran Mayer said. “Now we know that this has an effect not only on the metabolism but also affects brain function.”
The study opens up the potential for an entire new area of research into the connection between gut flora and brain function. For example, it raises the question of whether antibiotic use, particularly during early childhood, could actually harm the developing brain.
The researchers now hope to identify whether gut bacteria produce specific chemicals that send signals to the brain, as well as whether people who suffer from gastrointestinal problems experience changes in brain activity when their symptoms improve. Other researchers are examining whether probiotics in yogurt could lead to improvements in mood disorders such as anxiety.
Future research could focus on whether manipulations of gut flora could actually improve brain function, providing treatments for brain-related diseases such as autism, dementia or Parkinson’s disease.
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