The human gut is home to billions of bacteria that collectively form the gut microbiota, whose crucial role in digestion has long been known. But a growing body of scientific evidence is pointing out that these microorganisms also affect our behavior and even our brains. Now, the authors of a new systematic review show that bringing about a change in our gut flora can be an effective way to alleviate the symptoms of anxious states.
Researchers from Shanghai Jiao Tong University School of Medicine analyzed 21 studies focusing on interventions to treat anxiety through modulation of gut bacteria. The review, which involved 1,503 subjects and was published in the journal General Psychiatry, confirmed that some approaches are indeed effective.
To manipulate gut bacteria in participants, two main approaches were used: in seven of the studies included in the analysis, patients’ diet was changed, while in the other 14, probiotic supplements were administered. Probiotics, often referred to as “good bacteria,” are found in certain foods and can help rebalance depleted intestinal flora. Of the probiotic studies, seven used only one type of bacteria, two used two types, and the remaining five used three or more bacterial strains.
In all the studies reviewed, the Chinese researchers found a positive effect; in some cases it was small, but in eleven of them there was a marked improvement in anxiety symptoms: five through the probiotic approach and six through the dietary approach. The review also improved our knowledge regarding the combination of traditional anxiety medications with intervention on gut bacteria: to this propósito, the authors found that improvements occurred only when dietary interventions were combined with medications and not with probiotic intake.
Taken alone, the diet interventions had an 86 percent efficacy rate, which could be related to the more effective growth of different types of bacteria following the dietary regime change. Regarding supplementation with probiotics, however, experts speculate that the bacteria in the supplements might compete against each other and consequently fail to produce the desired changes to the gut microbiome. It is also possible that only certain types of bacteria make a difference, and identifying them will be the task of future research.
Yang B, Wei J, Ju P et al. Effects of regulating intestinal microbiota on anxiety symptoms: A systematic review
General Psychiatry 2019;32:e100056.
