Cinnamon aroma may promote social approach behavior toward unfamiliar groups

Graduate Student Yukiko Nishi, Professor Kazuhiro Shiozaki at the Department of Food Life Sciences, Faculty of Fisheries, Kagoshima University, and the Kampo Research Institute of Kracie (Representative Director and President Tetsuya Kusayanagi) announced on July 23 that they discovered in experiments using zebrafish that cinnamon (keihi) and its aroma component cinnamaldehyde promote social approach behavior. The researchers found that the compound activates the brain's isotocin system, the fish counterpart of the oxytocin system in humans. The findings are expected to lead to applications for the prevention and improvement of social frailty in older adults. The results were published in Food & Function.

Social frailty in older adults serves as a factor impairing healthy life expectancy because of isolation due to decreases in social activities accompanying aging. The development of intervention methods to maintain and promote social behavior and social participation is required. On the other hand, research on food-derived and crude drug components that enhance social behavior has been limited, and their mechanisms of action have remained poorly understood.

Thus far, the research group has searched for food components that can serve in the prevention and improvement of social frailty. They had previously shown that the Kampo formulation Ninjin'yoeito may improve social behavior. The researchers therefore analyzed the effects of keihi, one of its constituent crude drugs, on social behavior. When zebrafish were administered cinnamon or its primary aroma component cinnamaldehyde, social approach behavior toward unfamiliar fish of another species increased significantly, while no increase in aggressive behavior was observed.

Analyzing the mechanism of action revealed that administration of cinnamaldehyde increased isotocin levels in the brain. Isotocin is a neuropeptide involved in the regulation of social behavior and anxiety in fish and corresponds to oxytocin in mammals. When isotocin receptor activity was inhibited, the social behavior-enhancing effects of cinnamaldehyde disappeared. In addition, cinnamaldehyde was suggested to increase the liver-derived hormone FGF21, whose signaling activates the brain's isotocin system, thereby promoting social approach behavior.

By utilizing cinnamaldehyde, a major component of the crude drug keihi, which has long been used in Kampo medicine, as a food ingredient or crude drug, it may be possible to apply it to the prevention of social frailty in older adults and to the development of new health-promotion approaches.

Because cinnamon is widely used as both a food ingredient and a crude drug, and because its major component cinnamaldehyde is also widely used as a food flavoring, familiar and safe ingredients may be utilized.

Shiozaki commented, "In an aging society, social isolation and declining connections with society are important issues that are closely linked to healthy life expectancy and dementia. The discovery that cinnamon, which is widely used not only as a food ingredient but also in Kampo medicine, has this new function, and that we were able to clarify its mechanism of action, is a significant achievement. Going forward, we hope to build on these findings and further advance research that contributes to the prevention of social frailty and the extension of healthy life expectancy through the use of foods and Kampo medicines."

Journal Information
Publication: Food & Function
Title: Cinnamaldehyde, a major bioactive component of cinnamon bark, enhances social approach behavior associated with a liver-brain FGF21-isotocin axis in zebrafish
DOI: 10.1039/d6fo00815a