Food for thought: probiotics alter brain chemistry

31 August 2011
Posted by Chris Smith.

Exposure to probiotic bacteria can alter brain chemistry and calm anxiety Probiotic Drinkresponses, new research has revealed.

Mice fed a diet enriched with Lactobacillus rhamnosus, a common probiotic consitutent, showed significant reductions in stress and depression-related behaviours, and lower levels of the stress hormone cortisol, compared with control, broth-fed animals.

The numbers of chemical receptors for GABA, one of the brain's inhibitory neurotransmitters, also changed significantly during the experiments, particularly in a number of brain regions known to play a role in mood and stress responses.

Critically, these effects could be abolished by cutting the Vagus nerve, the main connection between the brain and the intestines. In mice that underwent this procedure, administration of the probiotic bacteria subsequently had no effect compared with broth-fed animals.

The work, published in the journal PNAS by University College Cork scientist Javier Bravo and his colleagues, is the first to show a direct effect on the brain and behaviour of animals administered probiotics similar to those used by humans.

As yet, say the researchers, it's not known how the effect is being achieved other than by some local host-microbe intestinal interaction that is signalled centrally to the brain via the Vagus nerve. It's also likely that, alongside GABA, other nerve-transmitter chemicals are likely to be impacted too, although this wasn't directly studied in the present series of experiments and remains as food for thought for future experiments.

What the new findings unequivocably confirm, however, is that you clearly are what you eat...

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