Mounting evidence is pointing to a powerful connection between the gut and the human brain, with the latest research coming from neurobiologists at Oxford University. Their findings are compelling and have promise for the management and future direction for treatments of depression and anxiety.

Inside the human body are trillions of microbes, collectively knows as the microbiome. When taken together, they are estimated to weigh about twice the weight of the average human brain. Think about that.

They live in the gut and their job is to digest food, synthesize vitamins and fight infection. What we are discovering is that their reach extends far beyond the gut, and all the way to the brain.

Studies over the last decade have identified the role of gut microbiome in maintaining certain brain functions such as mood, emotion and appetite. Research is increasingly pointing to the role it plays in psychiatric and neurological disorders such as anxiety, depression and autism. 

Researchers at the University of Oxford have found that taking probiotics has an effect on anxiety and depression by influencing the neuroendocrine stress response and by altering the way people process emotional information. 

The Study – What They Did

45 women between the ages of 18 to 45 took either a prebiotic or a placebo every day for three weeks.

(Probiotics consist of strains of good bacteria. They use prebiotics – carbohydrates they break down for nourishment – to multiply.)

At the end of the three weeks, the participants performed a number of tests involving positive and negative words, to measure how they processed emotional information. 

What They Found

Those who took the prebiotic paid less attention to negative information and more attention to positive information compared with those who took the placebo.

This effect is similar to that facilitated by antidepressants or anti-anxiety medication.

The prebiotic group also had lower levels of cortisol (the stress hormone) compared with the placebo group. High cortisol levels have been linked with anxiety and depression.

 Adding to the promise of the findings is research out of France that found that people who took probiotics for 30 days had reduced levels of somatisation (physical symptoms such as pain and tightness that are brought on by psychological distress), depression, anger-hostility and anxiety.

Early evidence for a gut-brain connection came from a study led by Dr Kirsten Tillisch of UCLA’s School of Medicine.

In their study, women who ate probiotic yoghurt (containing containing probiotic strains such as Bifidobacterium animalis, Streptococcus thermophiles, and Lactobacillus bulgaricus) twice a day for a month showed alterations in brain function, particularly in the brain’s response to the environment.

This was compared to women who ate a dairy product without any living bacteria and another group who ate no dairy products.

Brain scans revealed that those who took the probiotics had reduced activity in the area of the  brain involved in processing emotions.

Tillisch explains, ‘When we consider the implications of the work, the old sayings, ‘you are what you eat’ and ‘gut feelings’ take on new meaning.’

‘Time and time again, we hear from patients that they never felt depressed or anxious until they started experiencing problems with the gut.

Though probiotic cocktails aren’t likely to replace conventional treatments any time soon, there is compelling evidence to suggest great potential in using them as part of a treatment or management plan for anxiety or depression.