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Your Sense Of Smell Is Better At 9 PM Than At 3 AM

In 2017, scientists found a link between peoples' senses of smell and their circadian clocks.

an aged limestone nose and mouth

The Image is The Nose and Lips of Akhenaten ca 1353–1336 B.C. (Metropolitan Museum of Art Open Source Archives)

In 2017, a study found that people’s sensitivity to smell changes over the course of a day, with an average peak around 9 PM and a low ebb between 2 AM and 10 AM.

Circadian Clocks

The shift in sensitivity appears to be tied to our circadian clocks—a biological oscillating phase that affects almost all the body’s organs and is synchronized to solar time. Other living things also have circadian clocks.

This lets us anticipate daily environmental changes that come with the day-night cycle. So for example, your body knows to start releasing more melatonin when it gets darker out in anticipation of sleep.

Researchers at Brown University hoped to determine if adolescents’ sense of smell was stronger or weaker at certain times of day—perhaps changing the allure of food aromas during those times. Based on evidence found in their study, there was a link between the ebbs and flows of smell and a person’s circadian rhythms.

The Plateaus, Ridges, And Valleys of Scent

While we still don’t know all the details, these findings could have implications for ongoing studies about obesity. Piqued sensitivity to smell might lead adolescents to eat more or to overeat.

Though, other research has found that the ability to detect smell is actually lower on average in adolescents with simple obesity, which results when calorie intake exceeds energy-use.

But we know with certainty that sensitivity to smell does change throughout the day. More work will need to be done to understand if how we eat is based on when our noses work best.

If you want to keep thinking about how people’s sense of smell influences their eating habits, click here.

Thank you to Rachel Herz of Brown University for reviewing this episode’s script.

Sources And Further Reading:

  • Brown University. “Smell sensitivity varies with circadian rhythm.” ScienceDaily. October 26, 2017. Accessed April 23, 2018.
  • Herz, Rachel S. Van Reen, Eliza. Barker, David H. Hilditch, Cassie J. Bartz, Ashten L. Carskadon, Mary A. “The Influence of Circadian Timing on Olfactory Sensitivity.” Chemical Senses, Volume 43, Issue 1, 25 December 2017, Pages 45–51, https://doi.org/10.1093/chemse/bjx067
  • Ryan, Cate. “Circadian rhythms linked to smell sensitivity.” The Brown Daily Herald. November 7, 2017. Accessed April 25, 2018.

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