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Saliva research wins Ig Nobel Prize for chemistry

October 01, 2019

By Mary Beth Versaci

Cambridge, Mass. –– Ever wonder how much saliva a typical 5-year-old produces in a day?

A team of Japanese researchers' efforts to answer that question won them an Ig Nobel Prize, a satiric award modeled after the Nobel Prize that honors "achievements that make people laugh and then think."

Produced by the science humor magazine Annals of Improbable Research and co-sponsored by the Harvard-Radcliffe Society of Physics Students and the Harvard-Radcliffe Science Fiction Association, the 29th annual Ig Nobel Prize Ceremony took place Sept. 12 at Harvard University's Sanders Theatre in Cambridge, Massachusetts.

Drs. Shigeru Watanabe, Mineko Ohnishi, Kaori Imai, Eiji Kawano and Seiji Igarashi won the chemistry prize for determining 5-year-old children produce an estimated 500 milliliters of saliva per day.
Ig Nobel Prize Saliva image 3
Winner: Dr. Shigeru Watanabe explains how he conducted his research into how much saliva a 5-year-old produces daily. His work won this year's Ig Nobel Prize for chemistry. Photo from Ig Nobel Prize Ceremony video
The study involved 15 boys and 15 girls. Using their saliva flow rates while eating, awake but not eating, and sleeping, as well as the time they spent each day on those activities, the researchers were able to calculate their estimated total saliva production.

They published their findings in August 1995 in the Archives of Oral Biology. At the time, they were working for the Health Sciences University of Hokkaido School of Dentistry's Department of Pediatric Dentistry.

Dr. Watanabe attended the ceremony with his three sons –– who were some of the original research subjects –– and accepted the award on behalf of his team.

"We found out [an] important fact, that [the] total saliva volume per day in 5-year-old children [is] 500 milliliters," he said, holding up a water bottle to illustrate the amount.

His sons also demonstrated part of the experiment by chewing bananas and spitting them into cups, which was greeted with laughter from the audience.
Ig Nobel Prize Saliva image 2
Flashback: Dr. Shigeru Watanabe's sons reenact the role they played as children as part of their father's study to determine how much saliva a 5-year-old produces daily. Dr. Watanabe's work was honored Sept. 12 during the 29th annual Ig Nobel Prize Ceremony at Harvard University. Photo from Ig Nobel Prize Ceremony video
This was the second year in a row the Ig Nobel Prize for chemistry honored research involving saliva. In 2018, a team from Portugal won the award for measuring the effectiveness of human saliva as a cleaning agent for dirty surfaces.

Saliva supports the health of soft and hard tissues in the oral cavity. ADA members can read about oral health topics related to saliva by going to ADA.org/en/member-center/oral-health-topic.