Uplift for Rats Feeling Down

Lactobacillus casei is one of the eight bacterial strains included in a probiotic cocktail shown to ameliorate depression-like effects in rats with poor diets.

Winclove Probiotics

In humans, research suggests that a poor diet can lead to depression, and that depression can lead to a poor diet, but the mechanisms for this bidirectional link are unclear. As interest in the gut microbiome has grown alongside studies of probiotics, or ingested microorganisms, researchers have begun to examine whether the interactions between diet and brain may be mediated by probiotics. A new study shows that—at least for one strain of rat—ingesting probiotics can protect against the depression-like symptoms caused by a poor diet.

To determine if microbes might link lifestyles and mood, Anders Abildgaard at Aarhus University in Denmark and other Danish scientists tested a genetic line of rats specifically bred to exhibit depression-like symptoms (Flinders Sensitive Line, or FSL rats), which were further exacerbated by a high-fat diet. One group of FSL rats was given a healthy diet; another a high-fat, low-fiber diet. Those two groups were each further split, with some rats given ordinary drinking water and the rest provided water dosed with a probiotic cocktail of eight bacterial strains.

To test for depression-like symptoms, rats “are put in a container with water, and we study how the rat behaves,” explains Abildgaard. Some rats struggle vigorously to get out. Others are more passive and give up, apparently in despair. More time spent immobile and less time spent struggling for survival is taken as a depressive-like behavior.

Compared to the group of rats fed the healthy diet, FSL rats on the high-fat diet exhibited greater depressive-like behavior, spending more time immobile. However, probiotic treatment appeared to mitigate the depressive-like effects of a poor diet. Rats who received probiotics with their high-fat diet were more mobile than those rats on the high-fat diet who received ordinary water. For rats consuming the healthy diet, probiotics had no effect on their forced swim test results.

“We didn’t really expect to see such dramatic changes,” says Abildgaard. Although these research findings cannot be extrapolated beyond rats, Abildgaard hopes his work will spark future research to examine possible links among diet, probiotics, and depression in humans. (Brain, Behavior, and Immunity)