A new small study shows that drinking a fermented dairy beverage improves memory in healthy adults. People who consumed kefir exhibited improvements in relational memory – the capacity to remember associations between objects, places, people, or events, such as associating a name with a face.

The study involved 26 healthy young adults. About half of the participants consumed an 8-ounce serving of kefir (a yogurt-like probiotic drink) daily for four weeks, while the other half consumed an 8-ounce serving of low-fat, lactose-free milk. After a two-week washout period, the two groups switched beverages for an additional four weeks. Researchers assessed the participants' relational memory, mood, and microbiota composition before and after each intervention.

They found that participants who consumed the kefir showed improvements in their relational memory. In addition, the number of Lactobacillus bacteria in their guts increased by 235 percent. However, the researchers did not identify any associations between microbiota changes and memory performance or mood, a finding that may have been related to the small study size, according to the study’s authors.

Lactobacillus bacteria are among the most abundant bacterial species in the human gut. They are commonly referred to as “good bacteria” due to their beneficial effects on human health, particularly that of the gut. Learn about Lactobacillus reuteri, a type of Lactobacillus that strengthens the gut barrier, reducing leakiness and potentially influencing brain health.

• Read study abstract.