People who suffer from anxiety symptoms may find some relief by regulating their gut microorganisms through the use of both probiotic and non-probiotic food and supplements, according to a new review of studies published in the journal General Psychiatry.
Increasingly, research has shown that gut microbiota — the trillions of microorganisms in the gut which perform important functions in the immune system and metabolism by providing essential inflammatory mediators, nutrients and vitamins — can help regulate brain function through the “gut-brain axis.”
Recent research also suggests that mental disorders can be treated by regulating the intestinal microbiota, but some of this evidence has been conflicting. A research team from the Shanghai Mental Health Center at Shanghai Jiao Tong University School of Medicine in China conducted an analysis to determine if there is any solid evidence supporting the improvement of anxiety symptoms by regulating intestinal microbiota.
Intestinal microbiota can be altered through the use of probiotic supplements or other non-supplement ways like changing one’s diet. Probiotics are living organisms found naturally in some foods and are considered “good” or “friendly” bacteria, because they fight against harmful bacteria.
The researchers looked at 21 studies involving 1,503 people collectively. Of these, 14 studies had chosen probiotics as interventions to regulate intestinal microbiota (IRIFs), and seven chose non-probiotic ways, such as adjusting daily diets.
Importantly, the researchers found that the probiotic supplements used in seven of these studies contained only one kind of probiotic; two studies used a product that contained two kinds of probiotics; and the supplements used in the other five studies included at least three kinds.
In total, 11 of the 21 studies showed a positive effect on anxiety symptoms by regulating intestinal microbiota, meaning that more than half (52 percent) of the studies showed this approach to be effective, although some studies that had used this approach did not find it worked.
Of the 14 studies that had used probiotics as an intervention, more than a third (36 percent) found them to be effective in reducing anxiety symptoms, while six of the remaining seven studies that had used non-probiotics ways to regulate the gut found those to be effective — an 86% rate of effectiveness.
Some studies had used both the IRIF approach and treatment as usual. In the five studies that used treatment as usual and IRIF as interventions, only studies that had conducted non-probiotic ways got positive results, that showed a reduction in anxiety symptoms.
Non-probiotic interventions were also more effective in the studies that used IRIF alone. In those studies only using IRIF, 80 percent were effective when using non-probiotic interventions, while only 45 percent were found to be effective when using probiotic ways.
The authors say one reason that non-probiotic interventions were more effective than probiotic supplement interventions may be due to the fact that changing one’s diet (a diverse energy source) could have more of an impact on gut bacteria growth than introducing specific types of bacteria in a probiotic supplement.
In addition, since some studies had involved introducing different types of probiotics, these could have fought against each other to work effectively, and many of the intervention times used might have been too short to significantly increase the abundance of the imported bacteria.
“We find that more than half of the studies included showed it was positive to treat anxiety symptoms by regulation of intestinal microbiota,” write the researchers.
“There are two kinds of interventions (probiotic and non-probiotic interventions) to regulate intestinal microbiota, and it should be highlighted that the non-probiotic interventions were more effective than the probiotic interventions. More studies are needed to clarify this conclusion since we still cannot run meta-analysis so far.”
They also suggest that, in addition to the use of psychiatric drugs for treatment, “we can also consider regulating intestinal flora to alleviate anxiety symptoms.”