Good Mood Food? The link between bacteria and behaviour


I remember well, as a child, being told to steer clear of any dogs we met on holiday – just in case they had rabies. A rabid dog is something of a horror story, but it is also a display of how dramatically a microbe can affect and alter behaviour.

Dogs infected with rabies start to ‘foam at the mouth’, as their mouth overflows with virus-filled saliva. Previously calm, friendly dogs will go looking for a fight, as they are driven by the need to bite another dog to pass the infection on.

This change in behaviour and brain function is not limited to rabid dogs. There are many examples, in animals and humans, of a microbe (or a change in our microflora) changing behaviour.


One fascinating area of research is the potential link between gut bacteria and the development of autism.

Several studies have shown that many children diagnosed with autism spectrum disorders also suffer from gastro-intestinal issues.

Researchers considering this link have found that children with autism gain improvements, not just in their gut health but also in their behaviours, when supplemented with good bacteria. (1)


Other researchers have been delving into whether, as adults, the state of our microbiome has an impact on our mood and stress levels.

They have discovered that the bacteria residing within the microbiome produce dopamine and serotonin – 2 neurotransmitters associated with an improvement in mood. (2)

They have also found that boosting levels of certain, specific bacteria can have a beneficial effect on mood, revealing that:

• Supplementing with Lactobacillus rhamnosus can have beneficial effects in the treatment of depression and anxiety. (3)

• In one study subjects used a combination of Lactobacillus acidophilusLactobacillus casei and Bifidobacterium bifidum (2 billion of each) or a dummy pill, over 8 weeks. The patients who had received the probiotic combination had significantly decreased total scores on the Beck Depression Inventory. In addition, they had significant decreases in systemic inflammation. (4)

Written by Jenny Logan DNMed. (Jenny is a Nutritional Therapist who has worked with clients in health foods stores and private clinics for over 20 years)


(1) J. William Critchfield et al; The Potential Role of Probiotics in the Management of Childhood Autism Spectrum Disorders; Gastroenterology Research and Practice Volume 2011.

(2) Dr. Siri Carpenter; That gut feeling; September 2012 Monitor on Psychology

(3) Ingestion of Lactobacillus strain regulates emotional behaviour and central GABA receptor expression in a mouse via the vagus nerve; Javier A Brails et al; Proc Natl Acid Sci USA; 2011

(4) The effects of probiotics on depressive symptoms in humans: a systematic review; Caroline J Wallace; Ann Gen Psychiatry 2017

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