Millions of Americans suffer from anxiety, and new research has found that their symptoms could be alleviated by regulating the microorganisms in their gut using probiotic and non-probiotic food and supplements.

Gut microbiota is the trillions of microorganisms in the gut that perform important functions in the immune system and metabolism by providing essential inflammatory mediators, nutrients and vitamins.These gut microbiota also regulate brain function through a process called the “gut-brain axis,” and previous research has suggested that various mental disorders could be treated by regulating the gut microbiota.

A group of researchers at the Shanghai Mental Health Center at Shanghai Jiao Tong University School of Medicine recently decided to look into this further by reviewing 21 studies that had looked at 1,503 people collectively. Fourteen of the studies used probiotics as interventions to regulate intestinal microbiota (IRIFs), while seven chose non-probiotic ways, like adjusting daily diets.

Probiotics are living organisms found in some foods that have been designated as “good” because they fight dangerous bacteria and prevent them from getting into the gut.

In the end, 11 of the 21 studies showed that regulating intestinal microbiota was an effective way in lowering anxiety. In addition, more than a third (36%) of the 14 studies that used probiotics found this method to be effective in reducing anxiety symptoms. Six of the seven studies that used non-probiotics as interventions found those to be effective as well.

The expert believe that the reason why non-probiotics were so successful compared to probiotics was because changing diet can impact gut bacteria growth in a big way.

“We find that more than half of the studies included showed it was positive to treat anxiety symptoms by regulation of intestinal microbiota,” the researchers concluded. “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.”

These findings could play a huge role in how anxiety is treated in the future.