A review of 21 studies investigating the benefits of regulating gut microbiota on symptoms of anxiety has found that use of probiotic and non-probiotic foods and supplements may help to alleviate symptoms.
The NHS describes the feeling of anxiety as one of unease, worry, or fear that may be mild or severe. Anxiety is usually just a part of life: everybody experiences it before big events and tests or when something is unknown. Anxiety disorder is different. People who have it experience anxiety most days and often struggle to remember when they last felt relaxed. Symptoms can be both mental and physical, and while they vary between people, they can include feeling restless or worried, experiencing difficulties with concentrating and sleeping, and dizziness or heart palpitations.
Mental health charity, Mind, lists some possible causes of anxiety, including genetic predisposition, childhood trauma, life situation, physical health issues, and drugs and medication. The microbiota of the gut is another factor which has been implicated as a potential cause for anxiety disorder, and it is this, which has been investigated in the review published in the British Medical Journal (BMJ). More specifically, gut microbiota is a term used to describe the trillions of bacteria which colonise the gut and perform important functions in digestion and the immune system by providing essential inflammatory mediators, nutrients and vitamins.
Problems can arise when bacteria activate an inflammatory pathway, which can remain active in the long-term and can lead to changes in brain functions, eventually leading to symptoms of anxiety disorder. Gut microbiota have also been shown to affect the brain through the gut-brain axis, a bidirectional link between the two parts of the body which works through many pathways including the nervous system, immune system and endocrine system.
The microbiota of the gut is another factor which has been implicated as a potential cause for anxiety disorder, and it is this, which has been investigated in the review published in the British Medical Journal (BMJ)
The review, carried out by a team at Shanghai Mental Health Centre at Shanghai Jiao Tong University School of Medicine, looked at 21 studies, of which 14 had used probiotics as interventions to regulate intestinal flora (IRIF) and the remaining seven used non-probiotics. Probiotics are live strains of bacteria promoted as being ‘good’ or ‘friendly’. they are usually added to yogurt or drinks which are sold in supermarkets. Non-probiotic methods of regulating gut bacteria may include eating a specific diet. The goal here is to alter the existing gut microbiota without introducing new strains.
Overall, 11 of the studies had shown that regulation of gut bacteria had a positive effect on anxiety symptoms, this is 52 per cent. Though this does indicate a positive result the two groups of studies, probiotic vs non-probiotic, had widely differing results.
Gut microbiota have also been shown to affect the brain through the gut-brain axis, a bidirectional link between the two parts of the body which works through many pathways including the nervous system, immune system and endocrine system
For the 14 studies which used probiotics only 36 per cent reported a positive result, in comparison of the seven which used non-probiotic methods, six reported a positive result, equal to 86 per cent. Five studies had used both IRIF and normal treatment, and of this group only the studies which had used non-probiotic interventions found positive results.
Results suggesting that non-probiotic interventions are more effective in regulating gut bacteria than probiotic equivalents may be somewhat shocking initially, but the authors of the review attempted to give some potential reasons for this finding. Firstly, of the seven studies to use probiotics only one study used one, specific, kind of probiotic, two of the studies used two probiotics in conjunction, and the remaining five used at least three kinds. The use of multiple types of probiotic may have caused competition between the introduced bacteria which impaired the results.
[…] 11 of the studies had shown that regulation of gut bacteria had a positive effect on anxiety symptoms, this is 52 per cent
Another possibility is that the intervention times may not have been long enough to allow the bacteria introduced in the probiotic to grow enough to have significant impact.
As debilitating as anxiety disorder is it is also common, as studies have shown that up to 33.7 per cent of people will be affected by anxiety symptoms at some point in their lifetime. Though these results are promising for this huge group, regulation of gut bacteria is not a recommended stand-alone treatment, and people with these symptoms should consider seeking medical treatment.
This post was written by Molly Eastol and edited by Karolina Zieba.