Silvano Gallus, of Italy, waves as he receives the Ig Nobel award. AP

A study of whether pizza made and eaten in Italy wards off cancer and an inventor of a diaper-changing machine are among the winners of this year's spoof Nobel prizes.

Scientists who measured children's saliva were also honoured at the 29th annual Ig Nobel Prizes, which celebrate the sillier side of science.

The awards were due to be handed out on Thursday at Harvard University in Cambridge, Massachusetts.

Marc Abrahams holds up the 2019 Ig Nobel award at the 29th annual Ig Nobel awards ceremony. AP

The prizes aim to "celebrate the unusual, honour the imaginative — and spur people's interest in science, medicine, and technology," organizers said of the event, which features a traditional onstage paper airplane toss.

Fritz Strack of the University of Würzburg 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."

The winners receive $10 trillion in cash in essentially worthless, inflation-ravaged Zimbabwean money.

They were allotted 60 seconds to make a speech. If winners over-ran they were going to be cut off by an eight-year-old girl repeating, "Please stop, I'm bored."

Fritz Strack, of Germany, accepts his Ig Nobel award. AP

Like every year, the awards were going to be presented by real Nobel laureates, with four attending Thursday's ceremony.

A Japanese team took home the chemistry prize for estimating the total saliva volume produced per day by a typical five-year-old child.

Silvano Gallus won an Ig Nobel for his research that found yes, pizza is good for you. Well, maybe just pizza that's made and consumed in Italy.

"We found that pizza consumption in Italy was protective for many chronic diseases that are known to be influenced by diet: digestive tract cancers and infarction," Gallus, head of the Laboratory of Lifestyle Epidemiology at the Istituto di Ricerche Farmacologiche Mario Negri in Milan, Italy said in an email.

He noted that many pizza ingredients are associated with the Mediterranean diet, which has known health benefits.

Like many of the winners, Gallus, a renowned scientist, was thrilled to win an Ig Nobel.

Reuters