It was just last year that a certain company selling a special probiotic enhanced yogurt was ordered by a U.S. court to stop suggesting in its advertisements that it's product had health benefits that went beyond the norm. Now, new evidence by Javier Bravo and colleagues at University College Cork, suggests the company may have been on to something. In their paper, published in the Proceedings of the National Academy of Science, the team describes how mice given the prbiotic Lactobacillus rhamnosus, showed signs of being less anxious and depressed and even had lowered levels of stress hormones. Building on recent research that suggests there may be more of a gut-mind link than scientists have realized (such as depression and anxiety linked to bowel problems) Bravo and his team decided to look into probiotics and their possible impact on mood. In their research, they focused on Lactobacillus rhamnosus, a probiotic bacterium normally found in the gut, and which is also commonly found in various kinds of yogurt and other types of dairy products.
To find out if ingesting L. rhamnosus did indeed have any impact beyond normal nutritional value, the team fed half of a group of mice a broth heavily laden with the bacterium for a period of time; the other half were given the same broth without the probiotic. Afterwards, the mice were tested to see if any discernible behavioral changes resulted. Bravo et al found that the mice that had been given the probiotic demonstrated less anxious type behaviors, such as more of a willingness to traverse narrow walkways or to venture out into wide open spaces, activities that are known to cause stress in mice. They also found that the mice that had eaten the probiotic were less likely give in to the sensation of drowning when put in water, a sign that normally indicates depressive behavior. And finally, they found that the treated mice also had lower levels of stress hormones in their blood.