Drinking kefir, a probiotic dairy beverage, improves memory.

The community of microbes that comprise the gut microbiota act a bit like a sensory organ in the body, communicating information about the outside world to the brain and forming a gut-brain axis. Antibiotic and other medication use and changes in the diet can modulate the gut microbiota community in ways that reduce or increase the risk of neuropsychiatric illnesses such as depression. Findings of a recent report show that consuming a fermented dairy beverage may improve memory via changes in the gut-brain axis.

The hypothalamic-pituitary-adrenal axis (i.e., gut-brain axis) is formed by neural and endocrine connections between the hypothalamis, a brain region that controls body temperature, hunger, and sleep; the pituitary gland, a endocrine organ in the brain that produces hormones; and the adrenal gland, which is located above the kidneys and produces hormones that regulate stress such as adrenaline and cortisol. This axis of stress control communicates directly with the hippocampus, the memory center of the brain, which helps the brain retain memories of stressful situations, but also contributes to the development of depression. Previous research shows that probiotics can reduced depression severity; however, additional research is necessary to understand the mechanisms of this relationship.

The authors recruited 18 healthy adults and randomly assigned them to consume eight ounces of either kefir (i.e., a fermented dairy beverage with 12 strains of active bacteria) or low-fat lactose-free milk daily for four weeks. Participants completed questionnaires about their health, performed cognitive testing with electroencephalogram (EGG) measurement, and provided a fecal sample for the sequencing of the gut microbiome. After a washout period of about three weeks, participants switched to the opposite treatment and repeated the experiment.

The authors found that Lactobascillus bacteria more than doubled following kefir consumption suggesting significant change in the gut microbial community. Participants consuming kefir performed better on two measures of memory called misplacement and object-location binding. The researchers did not observe changes in depression scores in either group.

It’s important to note that more than 50 percent of participants in the study had a post-graduate degree, which could skew these results. Future studies in larger and more diverse populations are needed to better understand the effects of probiotics on the brain.

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