Health Benefits of Probiotics: Happiness?

by on December 24th, 2010
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If the recent scientific discovery on how probiotics affect mice holds true for humans, then you should eat your probiotic-enriched yoghurt and “feel” happy. Literally.

Eat Probiotics and “Feel” Happy

Probiotics are microoganisms that live in the gut and support the health of the host. All kinds of claims were made on the health benefits of probiotics, but happiness? Not yet. Be prepared. Television screens across the US may soon stream commercial videos of gloomy human faces bursting into joy at the taste of a spoon of yoghurt.

Scientists from Canada and Ireland have reported that the probiotic bacteria Lactobacillus rhamnosus have anti-depression and anti-anxiety effects in mice. In other words, scientists are saying that probiotics modulate emotional behavior, and they are presenting direct molecular evidence.

Probiotics and Brain Function

Scientists have long suspected interplay between gut probiotics and brain, and christened the link as “microbiotome-gut-brain axis”; evidences prove this link is disturbed in mice suffering from bowel disorders.

Even in humans doctors have recognized, what is referred to as comorbidity in medical terms, the interrelation between gastrointestinal problems and stress-related psychiatric disorders. However, so far, direct evidence linking bacteria living in stomach and stress response remained elusive. Well, the evidence is out; a recent research paper, published in the Proceedings of the National Academy of Sciences US, carries direct evidence.

Probiotics as Antidepressants

Scientists at the University College Cork, Ireland, and McMaster University, Canada, treated mice with Lactobacillus rhamnosus, a type of probiotic bacteria living in the gut, for 28 days and conducted a series of tests relevant to anxiety and depression. They discovered that mice treated with probiotics exhibited less stress and anxiety compared to the ones treated without the bacteria, and even the level of corticosterone, a stress-induced hormone, went down.

Interestingly, probiotics altered the expression of GABA receptors in the mice brain. GABA or gamma amino butyric acid is a neurotransmitter that modulates neuronal excitability and influences depression and anxiety.

Via the Vagus Nerve

What excited the scientists was their discovery that the stress relaxing effects of probiotics on mice brain takes place through the vagus nerve. When scientists surgically removed the vagus nerve, the mice no longer exhibited the stress relaxing effects of probiotics.

The involvement of the vagus nerve opens up new avenues of research, because vagus nerve stimulation has therapeutic benefits in brain seizures and late stage depression. Scientists suspect that the probiotics are up to something a little more than changing the mood of the mice. Getting to the bottom of it may open new opportunities for the treatment of depression, anxiety and many other psychological disorders.

Given the compelling evidence on direct influence of probiotics on brain function, scientists are understandably excited to conduct more experiments in this newfound area of interest. The days of doctors advising patients to “eat your yoghurt” may not be too far.


Javier A. Bravoa,, Paul Forsythe, Marianne V. Chew, Emily Escaravage, Hélène M. Savignaca, Timothy G. Dinana,, John Bienenstock, and John F. Cryan, Ingestion of Lactobacillus strain regulates emotional behavior and central GABA receptor expression in a mouse via the vagus nerve, Proceedings of the National Academy of Sciences, Vol:108, 16050-16055.

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