Probiotics and Stress Reduction

November 01, 2011

Could eating yogurt help reduce stress levels? A recent study suggests that bacteria-based food products may lessen anxiety as much as some medications.

Good digestive health may help to regulate and reduce stress in the brain, according to a recent study out of University College Cork in Cork, Ireland. The study looked at how potential probiotics, such as L. rhamnosus, affected the brain function of mice, and found that the presence of this bacteria in the gut altered behaviors relevant to anxiety and depression, modulated receptors in the brain known to be involved in anxiety and reduced the stress-induced elevation in corticosterone – a hormone that regulates stress.

There is increasing evidence revolving around what is now being called the microbiome-gut-brain axis, suggesting an interaction between the intestinal microbial (the bacteria in your stomach and intestines), the gut, and the central nervous system. By modifying the gut microflora in mice, researchers were able to see reductions in responses to stress and anxiety – extremely important considering the existing, known relationships between gastrointestinal disorders and stress-related psychiatric disorders.

Dr. John Cryan, Professor of Anatomy at University College Cork and one of the studies co-authors, says that the reason researchers wanted to show that that they could modulate brain and behavior in healthy mice (as opposed to those with gastric disorders) is that there have been some excellent studies in the past showing that probiotics can reverse some of the behavioral changes in mice following infection. 

“Our data expand this greatly and show that we don’t have to have an altered microiota or immune system for potential probiotics to have an effect,” he says.

Cryan says that another crucial aspect of this study was to show that, instead of working through immune or hormonal function, there was a direct neuronal route from the gut to the brain – a discovery that allows for specific therapies to be considered. Also, the study was reproduced at another lab at McMaster University, Canada, further solidifying the test results.

“Our data show that the relationship between the gut and the brain is through the vagus nerve, which is one of the main regulators of how the brain is able to sense what is going on in the rest of the body,” he says.

Researchers found that mice on this probiotic diet for a couple of weeks were more relaxed than their placebo-treated counterparts. Lower levels of stress hormones and anxiety were recorded. Cryan says they even saw changes in the chemical make up of the brain. In fact, some of the reactions were so robust that they mimicked the reaction one could receive from an acute injection of Valium®. 

The question everyone is now asking, from retailers to consumers, is should we be eating more yogurt? But Cryan says it’s too early to take that leap. And while the research opens up a myriad of possibilities, fundamental studies are needed to back up any such potential claims about foods human eat and their effects on the human brain. 

“Caution is needed at this point as there will be differences between the actions of probiotic yogurts from strain to strain – even within the Lactobacillus family. The strain we used is not commercially or clinically available. What we have done is demonstrated that there is potential for bacteria-based food products to have marked effects on brain and behavior,” says Cryan.

The next step is testing in humans, which Cryan says will most likely happen in the near future. The University College Cork research institute at the Alimentary Pharmabiotic Centre there has a large capability for human trials and is interested in following up with specific probiotic agents on brain and behavior. If translatable, Cryan says, these findings could prove to be useful therapeutic additions in stress-related disorders such as anxiety and depression.