In the News, Spring 2025: Probiotics May Reduce Negative Mood

A study published in the journal npj Mental Health Research has found that consuming probiotics may help reduce negative mood in healthy people and that daily monitoring may be a better way to measure improvements in mood, compared to methods used in past research.

In this randomized, double-blind study, 88 healthy adults used either a commercially available probiotic supplement or a placebo once daily for four weeks. The supplement contained nine bacterial strains common in the human gut. Participants took part in cognitive tasks that measure processing of stimuli, such as identifying facial expressions or responding to emotionally charged images. They also completed a wide range of psychological questionnaires. Researchers found that the probiotic group had reduced negative mood, such as irritability or sadness, after two weeks, based on daily monitoring.

Study author Katerina Johnson of Leiden University stated, “Although this study was using probiotic supplements, it’s relevant to note that there are natural sources of probiotics in our diet (e.g., fermented cheese, sauerkraut, kimchi) and also prebiotic fiber which helps promote the growth of beneficial gut bacteria and is found in various foods (e.g., bananas, legumes, whole grains). In fact, some of my other research on the human microbiome found that eating naturally occurring sources of probiotics and prebiotics was linked to a more diverse microbiome, typically a marker of a healthy gut.”

SOURCES:

Dolan EW. Probiotic supplements may reduce negative emotions in healthy adults. PsyPost, April 15, 2025. psypost.org/probiotic-supplements-may-reduce-negative-emotions-in-healthy-adults.

Johnson KVA, Steenbergen L. Probiotics reduce negative mood over time: the value of daily self-reports in detecting effects. npj Mental Health Res. 2025; 4:10. doi.org/10.1038/s44184-025-00123-z.