This study was published as a letter to the editor and therefore was not peer reviewed. The researchers wrote that “The demographics did not differ significantly between the two groups”, but very little of this demographic data was provided, making it difficult to confirm that the randomization process created appropriately balanced groups.

This study received funding support from Natural Way Co., Ltd., a GABA supplement manufacturer.

Although this study has shortcomings, its findings probably shouldn’t be discounted based on the idea that GABA does not cross the blood-brain barrier (and therefore can’t have an effect on sleep). For one thing, GABA receptors are present in a number of areas of the body (e.g, in the gut and certain immune cells), which are accessible to ingested GABA.^[1]^[2] It’s therefore possible that oral GABA could improve sleep via effects on these cells and tissues. Alternatively, whether ingested GABA actually can or cannot cross the blood-brain barrier in physiologically relevant amounts has not been conclusively demonstrated,^[3] (likely because such tests are extremely difficult^[4]).

GABA supplementation for improving sleep Original paper