Probiotics and The Human Brain

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Photo by Bradley Stemke
Photo by Bradley Stemke

A new study shows for the first time that probiotics in the diet can affect brain activity in humans.

Using functional MRI (fMRI), researchers discovered that women who regularly consumed foods with probiotics had altered activity in areas of the brain that process sensation and emotion.

It’s still unclear whether these changes are beneficial, since evaluating the effects will require additional research. However researchers hope to pursue studying how probiotics affect people with irritable bowel syndrome and anxiety.

Earlier research has demonstrated that gut microbiota can affect brain activity and behavior in mice, but this is the first study to show that probiotics can affect resting brain activity in humans.

“This gives credence to the idea that we may eventually modulate brain function in disease states using probiotics,” explained John Cryan, PhD, who led the earlier research on mice and probiotics, and commented on the new study for Medscape Medical News.

Dr.Cryan pointed out that they still have to investigate the mechanisms as to how the bacteria are affecting the brain.

The study, published in the journal Gastroenterology, included 36 healthy women with no psychiatric or gastrointestinal conditions. For four weeks, 12 women ate yogurt containing probiotics twice daily; another 11 ate a non-fermented milk product (control); and 13 women received neither intervention. The yogurt contained the probiotics Bifidobacterium animalis subsp Lactis, Streptococcus thermophiles, Lactobacillus bulgaricus, and Lactococcus lactis subsp Lactis.

Before and after the intervention, researchers used fMRI to test the women for resting brain activity and brain responses as they performed an emotion-recognition task. The task required participants to view a series of pictures of people with scared or angry faces and match them to other faces of people with the same emotions.

While performing the emotional-recognition task, women taking probiotics had significantly reduced activity in a functional network that includes affective, viscerosensory, and somatosensory cortices. But when they were resting, the women had increased connectivity  between the cognition-associated regions of the prefrontal cortex and the periaqueductal gray matter of the midbrain. These changes weren’t observed in women consuming non-fermented milk products or in the no-intervention group.

In future studies, the researches hope to identify signaling pathways between the microbiota and the brain. If their findings are confirmed, then modulation of the gut flora could potentially assist in the treatment of patients with abnormal pain and stress response.



Tillisch K, et al. Consumption of fermented milk product with probiotic modulates brain activity. Gastroenterology 2013; 144(7): 1394–1401.e4.

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