AMSTERDAM (CBS) – If you sometimes feel you focus too much energy on obsessing over past slights or regrets, you might want to add probiotics to your diet.

Researchers in the Netherlands say they provided 40 healthy study participants with a packet of powder that was to be mixed into warm water or milk every day for four weeks. One group received a placebo, while the other got a probiotics mixture.

At both the beginning and the end of the experiment, the participants had to fill out a survey on their depression levels.

Scientists founds that the subjects who were given the probiotics mixture were significantly less likely to ruminate over negative or past events.

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“Rumination is one of the most predictive vulnerability markers of depression,” psychologist and study author Laura Steenbergen tells ScienceDaily. “Persistent ruminative thoughts often precede and predict episodes of depression.”

Probiotics are live microorganisms often found in foods like yogurt, soft cheese and milk. They aid digestion and the immune system.

The research is published in the journal Brain, Behavior and Immunity.