Dietary changes to the bacteria living in our guts could have an impact on brain functioning, a new study suggests.


Researchers at the University of California, Los Angeles, found that regularly eating yogurt with probiotics, which contain "good" bacteria, seems to affect brain functioning in women. They said the proof-of-concept study shows it is possible to impact brain functioning by altering gut bacteria through diet.


The study, published in the journal Gastroenterology, was funded by Danone Research, which is the research arm of Danone, a company that produces yogurt and other dairy products. Some of the study researchers are Danone employees, but they had no role in the interpretation or analysis of results.


Researchers noted that past studies have shown a gut-brain connection in terms of the brain sending signals to the gut. But this new study shows that the gut could also send signals to the brain.


"This study is unique because it is the first to show an interaction between a probiotic and the brain in humans," study researcher Dr. Kirsten Tillisch, M.D., an associate professor at the Oppenheimer Family Center for Neurobiology of Stress at the UCLA David Geffen School of Medicine, told Medscape Medical News. "We can't say whether the effects are beneficial; that will take larger studies with more complex designs. One of the areas this will move to is study of disease groups like irritable bowel syndrome and anxiety."


The study included 36 women between ages 18 and 55, who were split up into three groups and assigned an eating regimen for four weeks. One group ate yogurt with probiotics two times a day, the second group ate a yogurt-like product that didn't have probiotics, and the third group ate neither. Researchers had the study participants undergo imaging scans before and after the four-week period, as they completed a test where they had to match faces showing a certain emotion with other faces showing the same emotion.


Researchers found that that women who consumed the probiotics had changes in activity and engagement of certain brain regions. For instance, the insula brain region (involved in processing sensations that come from within the body) had decreased activity, and there was increased connectivity between parts of the prefrontal cortex involved in cognition and a part of the brainstem, called the periaqueductal grey.


"Four-week intake of an FMPP [fermented milk product with probiotic] by healthy women affected activity of brain regions that control central processing of emotion and sensation," the researchers concluded in the study.


"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," study researcher Dr. Emeran Mayer, a professor of medicine at the university, said in a statement. "Now we know that this has an effect not only on the metabolism but also affects brain function."


According to the American Psychological Association, past studies in animals have also shown that altering gut bacteria in animals can produce more anxious or bold characteristics. In a 2011 study in the Proceedings of the National Academy of Sciences, researchers found that probiotics seemed to blunt physiological stress responses of mice, and also lowered their levels of stress hormone, compared with mice not fed probiotics.


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  • Digestive Health


    Each of us has more than 1,000 different types of bacteria that live in our digestive tracts, helping us to break down food and absorb nutrients. But when we take antibiotics -- medicine that is designed to kill destructive, illness-causing bacteria -- the drugs can also kill the healthy intestinal flora that helps us digest. About 30 percent of the patients who take antibiotics report suffering from diarrhea or some other form of gastrointestinal distress, according to the recent <em>JAMA</em> study on probiotics and antibiotic-associated diarrhea. As a result, doctors commonly prescribe taking probiotics to "repopulate" the digestive tract with healthful bacteria. The study found that it was a viable solution for many.
    <br><br>
    But probiotics can also help with other types of digestive issues. <a href="http://www.ncbi.nlm.nih.gov/pubmed/16863564" target="_hplink">Research has shown</a> that probiotics can be helpful for people with irritable bowel syndrome, or IBS -- a hard-to-treat condition that can have a range of intestinal symptoms, such as abdominal pain, cramps, bloating, diarrhea and constipation. In one study, female IBS patients experienced some alleviation of symptoms like abdominal pain and irregularity when they were given a supplement of the bacterial strain, Bifidobacterium infantis.
    <br><br>
    Even for those without an urgent problem, probiotics can help with overall digestive management. Challa argues in his book, <em>Probiotics For Dummies</em>, that good bacteria help "crowd out" bad bacteria. That's because the intestine is lined with adherence sites where bacteria latches on. If the sites are populated with good-for-you microbes, there's no place for a harmful bacterium to latch on.




  • Urinary Health


    Probiotics make a nice compliment to antibiotics among people who suffer from urinary tract infections, <a href="http://www.ncbi.nlm.nih.gov/pubmed/16827601" target="_hplink">according to the research</a>.
    <br><br>
    What's more, there's emerging evidence that regular probiotics can help <em>prevent</em> bad bacteria from invading the urinary tract by maintaining a population of healthy bacteria on the tract's adherence sites.
    <br><br>
    Infections of the urinary tract are extremely common, especially in women. Most infections disappear with antibiotics, but about 30 to 40 percent might return, <a href="http://www.umm.edu/altmed/articles/urinary-tract-000169.htm" target="_hplink">according to literature</a> from the University of Maryland Medical Center.




  • Allergies


    Allergy research is still preliminary, but at least one <a href="http://abcnews.go.com/Technology/AllergiesNews/story?id=4727318&page=1#.T7FHU59Ytvd" target="_hplink">large, high quality study</a> found a relationship between women taking probiotics during pregnancy and a 30 percent reduction in the instance of childhood eczema (an early sign of allergies) in their infants.
    <br><br>
    Researchers selected women who had a history of seasonal allergies -- or whose partners had histories of allergies. The infants who received probiotics in-vitro also had 50 percent higher levels of tissue inflammation, which is thought to trigger the immune system and reduce allergy incidence.




  • Women's Health


    Just like the digestive tract, the vagina relies on a precarious balance of good and bad bacteria. When that balance is off, it can result in one of two very common, though thoroughly uncomfortable infections: bacterial vaginosis and yeast infections. In fact, bacterial vaginosis can actually <em>lead</em> to a yeast infection.
    <br><br>
    Some small studies have found that <em>L. acidophilius</em> can help prevent infection, manage an already active one or support antibiotics as a treatment, though it's worth noting that the probiotics were taken as vaginal suppositories, rather than orally in food.
    <br><br>
    Probiotics may also have a special role in maternal health, as pregnant women are particularly susceptible to vaginal infections. And bacterial vaginosis has been indicated as a contributing factor to pre-term labor, making probiotics a potential boon for fetal health.




  • Immunity


    Surprisingly, <a href="http://www.med.umich.edu/opm/newspage/2006/hmprobiotics.htm" target="_hplink">one of the main functions</a> of healthful bacteria is to stimulate immune response.
    <br><br>
    By eating probiotic-rich foods and maintaining good intestinal flora, a person can also help to maintain a healthy immune system. And that has real world effects: for example, in <a href="http://www.ncbi.nlm.nih.gov/pubmed/15309418" target="_hplink">one small study</a> of students, those who were given a fermented dairy drink (instead of milk) displayed increased production from lymphocytes -- a marker of immune response.




  • Obesity


    In 2006, Stanford University researchers found that obese people had different gut bacteria than normal-weighted people -- a first indication that gut flora plays a role in overall weight.
    <br><br>
    Some preliminary research shows that probiotics can help obese people who have received weight loss surgery to maintain weight loss. And in a study of post-partum women who were trying to lose abdomnial fat, the addition of <em>lactobacillus</em> and <em>bifidobacterium</em> capsules helped reduce waist circumference.
    <br><br>
    It's still unclear how probiotics play a role in weight loss -- and there is some controversy about <a href="http://scienceblogs.com/obesitypanacea/2010/03/are_probiotics_the_cure_for_ab.php" target="_hplink">how significant the probiotics-associated weight loss is</a>.
    <br><br>
    But as long as the probiotics source is low-calorie and healthful, itself, it is an innocuous method to attempt.