A new study, conducted by the researchers at the UCLA's Gail and Gerald Oppenheimer Family Center for Neurobiology of Stress and the Ahmanson-Lovelace Brain Mapping Center at UCLA, now provides evidence for the effect of bacteria ingested in through food on the human brain.

Researchers already know that the brain sends signals to the gut, which is exactly why humans tend to develop gastrointestinal troubles and heartburn when undergoing chronic stress and depression. This study is all set to prove that it works the other way round as well, and that the state of the gastrointestinal system could impact the way the brain functions.

For this study, the researchers recruited 36 women, all between the age of 18 and 55 years, and divided them into three groups. One group was fed a specific yogurt that contained a mixture of several probiotics, which are thought to have a positive effect on the intestines, twice a day for four weeks. The second group was asked to consume a dairy product that looked like yogurt, but didn't really have any probiotics involved, and the last group was not asked to take anything.

MRI (Magnetic resonance imaging) was carried out both before and after the four weeks had passed, and looked at the brains of the women, both in a state of rest and in response to an emotional recognition task. The results they obtained finally confirmed the fact- women consuming probiotics had a greater connectivity between the brainstem region and the areas of the prefrontal cortex.

This new research is all set to pave way for new studies that may help determine the effects of other foods on the functioning of the brain, and how changes in brain function could help people suffering from gastrointestinal diseases like irritable bowel syndrome, bloating and abdominal pain better cope with their symptoms.

"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 study is expected to be published in the June issue of the journal Gastroenterology.