Scientists find probiotics reduce stress


SCIENTISTS IN Cork believe they have proved that consuming probiotic bacteria can alter brain chemistry involved in stress and anxiety.

“This is the first time it has been shown that probiotics in the gut can directly affect the brain,” said Prof John Cryan, professor of anatomy at University College Cork.

Prof Cryan is also a Science Foundation Ireland funded principal investigator at Cork’s Alimentary Pharmabiotic Centre. Researchers there study probiotics, which Prof Cryan describes as bacteria that when eaten can deliver proven health benefits.

He joined with researchers in Cork and at McMaster University in Canada to study how probiotics might affect stress levels in laboratory mice.

Details of their work are published this morning in the US publication Proceedings of the National Academy of Sciences.

What you eat can have a direct effect on how you feel and how your brain and body respond. This happens in part because of the vagus nerve which provides a direct connection between the stomach and the brain.

If you pick up a stomach bug the vagus nerve helps to transfer the sick feeling and malaise. “The vagus is involved in all aspects of signalling from the gut to the brain,” he said. The question was, could good bacteria also affect the brain via this nerve.

The research showed conclusively that it could, he said. The brain chemistry of mice fed with probiotic Lactobacillus rhamnosus JB-1changed, with fewer stress, anxiety and depression-related behaviours compared to mice fed with broth.

Ingesting the bacteria pushed down levels of the stress hormone corticosterone. It also changed the action of GABA, a brain chemical acting directly on nerves to dampen down activity.

Prof Cryan, who collaborated at the Cork centre with Dr Javier Bravo, Dr Héléne Savignac and Prof Ted Dinan, said the finding could have important implications in the treatment of anxiety and depression-related disorders in humans. He is keen to begin human trials, given this probiotic is already known to be safe for consumption, and could help treat psychiatric conditions without the use of drugs.

The big question is how the probiotic can do this, he said. “Either the bacteria is interacting directly with the vagus nerve or there is a substance that is activating the vagus nerve.”

He believes that the brain chemistry change will not be common across other probiotic organisms. Even so others are being tested to see if they also have this effect.