0456 GMT June 19, 2019
Probiotics and sticking to a balanced diet have both been found to have a positive effect on symptoms, dailymail.co.uk wrote.
Eating more fruit and vegetables appears to be the most beneficial intervention for boosting 'good bacteria', scientists said.
The Chinese research is the latest in a long line of studies to link mental health to microorganisms found in the gut.
Researchers from the Shanghai Jiao Tong University School of Medicine reviewed 21 studies that looked at 1,503 people all together.
Around two thirds of them, 14, had chosen probiotics as interventions and seven chose non-probiotic ways, such as adjusting daily diets.
Probiotics are found in foods, such as kefir, yoghurt, sauerkraut, miso and pickles, and are also made into supplements with various strains.
Overall, more than half (52 percent) of the studies, 11, showed regulating intestinal microbiota had a positive effect on anxiety symptoms.
Of the 14 studies that had used probiotics as the intervention, more than a third (36 percent) found them to be effective in reducing anxiety symptoms.
Six of the seven studies that had used non-probiotics as interventions found those to be effective — an 86 percent rate of effectiveness.
Some of the 21 studies had tried to improve gut bacteria while also allowing treatment as usual, such as anti-anxiety medication. But there were only reductions in anxiety symptoms with non-probiotic studies, compared with probiotic ones.
The researchers believe interventions to improve gut bacteria without probiotics, ensuring a diverse range of foods, is more successful at bacteria growth.
Writing in the journal General Psychiatry, they said further trials are needed to confirm the findings.
They added: 'There are two kinds of interventions (probiotic and non-probiotic interventions) to regulate intestinal microbiota.
“It should be highlighted that the non-probiotic interventions were more effective than the probiotic interventions.
Within the 14 studies that use probiotics, between one and five types of probiotic were used.
The researchers said this could lead the probiotics to fight against each other to work effectively.
It may take a long time — more than the length of the studies — to significantly increase the abundance desired bacteria.
The authors acknowledge some limitations, such as differences in study design, subjects, interventions and measurements.
But they said the quality of the studies was high, and they suggest consideration of regulating gut bacteria to alleviate anxiety symptoms.
There is evidence trillions of bacteria in the gut influence parts of the brain involved in emotion by a communication path known as the 'brain-gut axis'.
Physical and chemical connections between your gut and brain, including millions of nerves and neurons, influence the role of either 'organ'.
The close interaction between the two can explain how digestive juices start being produced when our brain sees food or begins eating, or why we feel sick when nervous or anxious.
Most people have feelings of anxiety at points, but it is considered a mental health problem if it impacts a person's ability to live their life.
Physically, people who suffer with anxiety regularly cope with panic attacks, sweating, teeth grinding, nausea, or dizziness.