Circadian clocks control our sense of smell

“The circadian clock affects virtually every organ system in the body” writes Dr. Leslie Vosshall, a researcher at Rockefeller University who studies smell. If we understand the circadian rhythm in our body as a biological sleep and wake indicator, then all other cells in our body must grasp this cycle in the very same way. 

The New York Times recently published an article that outlines a new test made to study how circadian rhythm affects our sense of smell – and while the results don’t come as a grandiose surprise, they are interesting enough to reiterate – because it feels as though research is only in its embryonic phase when it comes to how these natural rhythms affect our biological mechanisms.

Within a research to test whether the sense of smell and taste have an affect on adolescent obesity, Rachel Herz, a sensory researcher at Brown University, and her team conducted a controlled test to check if the intensity of smell and taste varies throughout the day – and what role does circadian rhythm have in this shift.

Over a period of nine days, 36 adolescents ranging from the ages of 10 to 15 were invited to partake in a smell and taste experiment, where they were given the same intensity of rose smelling substance in different periods of the day. When added together the results showed that the circadian rhythm does affect the sense of smell and that on average, the adolescent’s smell was most sensitive in the evening, around 9pm, and at its least sensitive between 2am and 10am. Melatonin tests were used to determine at what stage the participants were in their circadian cycle.

What does that tell us about our metabolism processes, and the connectivity between smell and hunger? It’s said that eating in the late hours of the evening is not optimum for our metabolism, yet our circadian rhythm – especially in young adults – directs us otherwise.

The ramifications of this study are still to be discovered, but what’s for certain is: a rose will smell different in the morning than it will in the evening.