Probiotics Could Protect Against Stress


Researchers at the University of Colorado Boulder have found a type of probiotic bacteria that protects the brain against the harmful effects of stress.


A growing weight of evidence shows that gut bacteria play a significant role in “brain health,” with gut microbiome imbalances being linked to a variety of neurological conditions including anxiety, depression, stress, fear and Alzheimer’s disease.

This connection between the brain and intestinal flora is known as the gut-brain axis.

And it’s not a one-way street.

Not only does the absence of certain beneficial microbes lead to mood disturbances, but stress, for example, has been shown to harm gut health just as much as junk food!

This knowledge led researchers to ask whether it’s possible to design a probiotic to protect us from such mood disorders.

Scientists at the University of Colorado Boulder had previously shown that mice injected with a bacterium called Mycobacterium vaccae were less anxious when confronted with a dangerous situation and also less likely to develop inflammation or colitis.

Now, in a study published in the journal Brain, Behavior, and Immunity, researchers show that Mycobacterium vaccae has anti-inflammatory properties that could be used to fend off stress.

To understand how M. vaccae affects brain function, the team injected the bacterium in male rodents once per week for three weeks. Eight days after the final injection, the researchers found increased levels of an anti-inflammatory protein called interleukin-4 (IL-4) in the rodents' hippocampi.

The hippocampus is a part of the brain that is important for learning and memory and plays a key role in processing feelings and "fight-or-flight" responses. Consequently, the hippocampus regulates our fear and anxiety responses.

In addition to higher levels of IL-4, the researchers found low levels of a stress-induced protein (called an “alarmin”), and higher levels of a receptor whose main role is to preserve the anti-inflammatory properties of the brain's immune cells.

So, what does that all mean?

Ultimately, the data suggest that M. vaccae promotes an anti-inflammatory environment in the brain, which creates a lasting resilience to the effects of stress.

If these findings can be replicated in humans, they will have a huge impact on neuroinflammatory disorders.  



Frank, M et al. Immunization with Mycobacterium vaccae induces an anti-inflammatory milieu in the CNS: Attenuation of stress-induced microglial priming, alarmins and anxiety-like behavior. Brain, Behavior, and Immunity. 2018; May 26 DOI: 10.1016/j.bbi.2018.05.020