Probiotics & Mental Health

photo credit:  Jules

photo credit: Jules

You are what you eat!

First of all, you’re probably aware that there are complex and diverse microbe communities in our guts which help to regulate our metabolism and immune systems.  Well, in recent years there’s been a buzz about how these gut microbes may affect mental health.  This is super exciting because someday, when we learn a lot more about it, it might mean new, natural options for regulating mood. 

In case you haven’t heard, let’s start with a fun and interesting NPR animation about the human microbiome, its function, and how to support it:  

New studies suggest that probiotics may actually help in mitigating anxiety and depression symptoms, and decreasing emotional reactivity.  Some studies show that probiotics can increase emotional resilience, decrease depressive thoughts, and lower levels of cortisol (a stress hormone, also relevant to metabolism, and how the body stores fat).

At this point, more research is needed, but as an adjunct treatment for depression, it seems possible that a bowl of yogurt in the morning might be a good idea.  It's clear that there is a powerful brain/body connection where emotions can disrupt digestion and digestion, in turn, can affect emotions.

Most of the studies thus far have been conducted on animals.  But the results have been so impressive that researchers are creating more human studies.

The first study I heard about was a small stress test study conducted at the University College Cork, Ireland. This study found that probiotics have a direct impact on mood neurotransmitters in mice.  The mice who received the probiotics took more than twice the risks of mice who received the placebo, and were less likely to give up in a life or death situation, suggesting reduced anxiety. The effects of probiotics were comparable in significance to those seen in study mice for antidepressant drugs.  Brain changes were reflected in the hippocampus, an area of the brain that regulates emotion and mood.  They showed half of the corticosterone (a stress hormone) and also a redistribution of brain receptors for GABA neurotransmitters, the same receptors affected by anti-anxiety medications like Valium.  These differences only held when the vagus nerve, which allows communication between the guts and the brain, was intact, indicating that the vagus nerve is crucial to the process.  

UCLA did a small study of women who ate probiotic dairy and found that they showed a decrease in emotional reactivity when doing an emotion recognition test where they had to match up pictures of angry and frightening faces. The researchers further found that brain effects could be seen in sensory processing areas of the brain, not just those associated with emotion.

The gut microbe community is reflected in the physical structure of the brain; this may be one reason why brain function is different from person to person.  A question this raises is how do repeated courses of antibiotics affect the brain, especially the developing brains of children?  Might there be any long-term consequences?  I don't have an answer to this, but I'm curious.

Oxford University did a study on prebiotics, carbohydrates that healthy bacteria feed on:

“After the three weeks had passed, the researchers completed several computer tests assessing how they processed emotional information, such as positive and negatively-charged words.

The results of one of the tests revealed that subjects who had taken the prebiotic paid less attention to negative information and more attention to positive information, compared to the placebo group, suggesting that the prebiotic group had less anxiety when confronted with negative stimuli. This effect is similar to that which has been observed among individuals who have taken antidepressants or anti-anxiety medication.”

Leiden University, Netherlands did another study on how probiotics affect emotional resiliency:

“The people who took probiotic supplements began to see improvements in their moods; they reported less reactivity to sad moods than those who took placebos. In other words, the people who took probiotic supplements were better able to overcome sad moods than the others, and thus had fewer depressive thoughts following bouts of sadness.”

A study done by the ETAP (Ethologie Appliquée) lab in France found that people who took probiotics for 30 days had decreased levels of psychological distress.

All of these studies support the hypothesis that there is a strong connection between gut bacteria and mental health, that probiotics can alter the way people process emotional information, which, in turn, can affect behavior.  These findings need to be confirmed by further research, but it seems natural that the brain, an organ, would be affected by nutrition just as any other organ might. 

In the meantime, while waiting for these studies to be conducted, I’m going to be eating yogurt.

Other sources of probiotics