Anxiety is a common mental health concern that impacts millions. A new study found evidence that anxiety symptoms may be improved by regulating intestinal microbiota.

Anxiety symptoms are common in mental diseases and a variety of physical disorders, especially in illnesses related to stress. Signs of anxiety may include feeling nervous, being restless or tense, having a sense of impending danger, panic, or doom, having an increased heart rate, and hyperventilation. Experiencing gastrointestinal problems, sweating, trembling, and feeling weak or tired are also common symptoms of anxiety.

Profound Gut-Brain Link

There has been a persistent link between mental health and bacterial diversity in the gut. Previous basic studies have shown that gut microbiota is able to regulate brain function through the gut-brain axis. Microbiota is a collective term for the microorganisms that live in or on the human body.

Chinese researchers from the Shanghai Mental Health Center at the Shanghai Jiao Tong University School of Medicine presented two kinds of intervention — use of probiotics and non-probiotic ways — to regulate the microbes in the intestinal microbiota.

"We find that more than half of the studies included showed it was positive to treat anxiety symptoms by regulation of intestinal microbiota," authors Beibei Yang, Jinbao Wei, Peijun Ju, and Jinghong Chen said in their abstract.

Interventions Regulating Intestinal Flora

The researchers conducted an observational study of 21 published studies with over 1,500 subjects to provide clarification and new ideas for clinical treatment.

Fourteen of the 21 studies investigated used probiotics as a potential way to regulate intestinal microbiota. This type of intervention is referred to as IRIF or interventions regulating intestinal flora. The other seven studies used various non-probiotic intervention methods, like changing the foods participants ate daily. The objective in these cases was changing the "good bacteria" in a person's gut in such a way that it would have a positive impact on anxiety levels.

The team found that 52 percent, or 11 of the 21 studies, displayed positive changes on anxiety symptoms through the regulation of intestinal microbiota. However, some studies found that IRIF didn't have an effect on anxiety.

Probiotics And Dietary Changes Can Regulate Gut Bacteria

Looking specifically at the 14 studies that involved probiotics, a total of 36 percent of the studies found them to be effective in reducing anxiety symptoms, while non-probiotic interventions had a higher effectivity or 86 percent positive effect.

Probiotics are living organisms found naturally in some foods and are considered "good" or "friendly" bacteria because they fight against harmful bacteria.

The researchers suggested several reasons why dietary changes may have a more profound effect on one's gut bacteria as compared to taking probiotics. First, food provides diverse energy sources for the gut bacteria, and changing the diet can regulate the bacterial populations. Second, different types of probiotics were introduced in the studies, resulting to varying effects, and lastly, the intervention times might have been too short to significantly increase the abundance of the imported bacteria.

"So we can easily find that although we can regulate the intestinal flora in two ways, the non-probiotic intervention is significantly better than the probiotic intervention," the researchers said.

However, more studies are needed to clarify the conclusion. The systematic review is published in the journal BMJ.