Researchers at Tokyo Medical and Dental University (TMDU) in Japan show that melatonin and its metabolites promote the formation of long-term memories in mice and protect against cognitive decline.

Researchers at Tokyo Medical and Dental University (TMDU) showed that melatonin’s metabolite AMK can enhance the formation of long-term memories in mice. Memory of objects were tested after treatment with melatonin or two of its metabolites. Older mice that normally performed poorly on the memory task showed improvements as dosage increased. The metabolite AMK was found to be the most important as melatonin failed to improve memory if it was blocked from metabolizing into AMK.

Walk down the supplement aisle in your local drugstore and you’ll find fish oil, ginkgo, vitamin E, and ginseng, all touted as memory boosters that can help you avoid cognitive decline. You’ll also find melatonin, which is sold primarily in the United States as a sleep supplement. It now looks like melatonin marketers might have to do a rethink. In a new study, researchers led by Atsuhiko Hattori at Tokyo Medical and Dental University (TMDU) in Japan have shown that melatonin and two of its metabolites help memories stick around in the brain and can shield mice, and potentially people, from cognitive decline.