National / Science & Health

How much saliva does a 5-year-old produce? An award-winning Japanese team has the answer in a drool-worthy study


For any parents wondering how much saliva their 5-year-old produces, a Japanese team has the answer: about 500 ml per day.

The discovery landed the team of five a “prestigious” Ig Nobel chemistry award, a spoof prize that aims to “celebrate the unusual, honor the imaginative — and spur people’s interest in science, medicine, and technology.”

Shigeru Watanabe, a professor of pediatric dentistry at the School of Health Sciences at Meikai University in Urayasu, Chiba Prefecture, accepted the prize on behalf of his team at the 29th First Annual Ig Nobel Prize Ceremony at Harvard University in Cambridge, Massachusetts.

The other, absent, recipients were Mineko Ohnishi, Kaori Imai, Eiji Kawano and Seiji Igarashi. It marks the 13th consecutive year a Japanese has won an Ig Nobel prize.

The quintet were a part of the aptly named study “Estimation of the total saliva volume produced per day in 5-year-old children” that was published by Hokkaido University in February 1995.

The 68-year-old Watanabe was accompanied by his sons, now grown up and producing an undetermined amount of saliva per day, who were among the 15 boys and 15 girls used as test subjects for the experiment conducted about 35 years ago.

Watanabe received his prizes — a trophy made out of a coffee cup, an essentially worthless 10 trillion dollar bill from Zimbabwe and a certificate from Richard Roberts, who won the 1993 Nobel Prize in Physiology or Medicine and who discovered “split genes.”

“We found out an important fact, that the total saliva volume per day in 5-year-old children is 500 milliliters,” he told about 1,100 audience members at Sanders Theater.

While on stage for the allotted 60 seconds, his son attempted to demonstrate the experiment at the instruction of his father before running out of time. “OK, eat. Chew, chew, chew, chew, and spit out.”

At the beginning of the experiment conducted in the 1980s, the collegiate team measured “unstimulated” saliva by having the children drip their saliva for five minutes into a container to be weighed.

The children also chewed and spat out six types of food for the professors to determine “salivary flow rates” when eating.

For the next two days, the team recorded the amount of time the children were awake, asleep, eating meals and snacking.

By determining the rates of saliva flow when “unstimulated” and when eating, they were able to estimate the amount of saliva produced by the average 5-year-old child.

The chemistry prize was one of 10 handed out at the ceremony, which had the theme of “habits.” The biology award went to an international team for its discovery that dead cockroaches remain magnetized longer than living ones. Other winners included researchers who studied whether pizza made and eaten in Italy wards off cancer and an inventor of a diaper-changing machine

The top honor in the anatomy category went to Roger Mieusset and Bourras Bengoudifa for their 2007 work measuring scrotal temperature asymmetry in naked and clothed postmen in France.

Fritz Strack, of the University of Wurzburg, in Germany, won the psychology prize for “discovering that holding a pen in one’s mouth makes one smile, which makes one happier — and for then discovering that it does not.”

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