This new study published in Nature Research looked at over a thousand different Bifidobacteria strains, investigating how they interact with their host (e.g. you and I).
The results showed that Bifidobacterium adolescentis stimulate the production of GABA, an inhibitory neurotransmitter involved in mood, anxiety, blood pressure, and pain.
The results of this study tie in nicely with other studies showing that probiotic bacterial strains can affect mood and cognition. Previous studies had also shown that a couple of other bifido species produced GABA, but this study showed that B. adolescentis produces the highest amount.
The bifido strains contain the gad gene that converts glutamate into GABA (similar to the human GAD1 gene).
GABA is needed in the right amount by the body. Too little can lead to excess excitatory neuoronal activity (including seizures and mood disorders), but too much GABA can impair thinking and lead to being slow and sleepy (like what happens with alcohol or Valium).
It is thought that GABA doesn’t cross the blood brain barrier – at least not in large amounts. But there are still some questions there, though. What is known is that there is two-way communication between the gut and the brain, commonly called the gut-brain axis.