Graphic health warnings like those on cigarette packets, showing rows of rotten teeth on cans of cola and other sugary drinks, could deter some young adults from buying them, a study has shown.

Sugary drinks are blamed for fuelling the obesity epidemic, but in spite of the large quantities of sugar they contain – nine teaspoons in a can of Coca Cola – they do not carry a red traffic-light warning, which is voluntary in the UK. Sugar taxes, like that recently introduced in the UK, may reduce sales, but obesity experts believe more action is needed.

Prof Anna Peeters from Australia’s Deakin University and colleagues looked at the feasibility of introducing health warnings about the links between sugary drinks and obesity, type 2 diabetes and tooth decay. They tried out four different kinds of warnings – from plain text about the disease risk, number of teaspoons of sugar, to a picture of rotten teeth.

The researchers showed the drinks with the warnings to 994 young adults, aged between 18 and 35. Participants were asked to imagine they were entering a shop, a cafe, or approaching a vending machine to choose one of 15 drinks to buy, some sugary and some unsweetened. Some of the sugary drinks had no label. Others carried a warning or a health star rating.

The effect was bigger than Peeters expected. All the warnings reduced the inclination of the subjects to buy the drinks, but there was a 20% drop in imagined purchases of those drinks bearing a picture of rotten teeth.

“If there was political palatability for graphic warnings, that [one] had the strongest effect, so that’s the one I would go for,” said Peeters at the European Congress on Obesity, where she was presenting her research.

“You are going to get pushback from the industry and possibly the community,” she said. “If you had good social acceptance of graphic warnings, you’d go for that. But if government found that too difficult the other three are pretty good too.”



In the study, there was a 20% drop in imagined purchases of sugary drinks bearing a warning picture of rotten teeth. Photograph: Handout

A written warning about the raised risk of type 2 diabetes as a result of obesity would not have quite the same impact as the picture, she said, “unless you go for amputations”, which can be a consequence of the disease.

Peeters said the study showed the potential of front-of-pack warnings to change people’s behaviour. “While no single measure will reverse the obesity crisis, given that the largest source of added sugars in our diet comes from sugar-sweetened drinks, there is a compelling case for the introduction of front-of-pack labels on sugary drinks worldwide,” she said.

Prof Jason Halford of Liverpool University, treasurer of the European Association for the Study of Obesity, said there was a need for manufacturers and retailers like the supermarkets to bring in traffic-light warnings on sugary drinks. If they do not, “We’d have to adopt something regulatory and the regulatory might be this. And it might be the most effective,” he said.

Barbara Crowthers, a Children’s Food Campaign coordinator, said: “There is definitely a role for honest and clear health labelling in discouraging people from consuming too many sugary drinks, alongside other measures such as product reformulation, marketing and advertising restrictions, tackling portion sizes and introducing price disincentives such as the UK’s new sugary drinks tax. Whilst, as we’ve seen on cigarettes, not everyone will be put off by graphic labels, making it clearer that consuming sugary drinks may also lead to the dentist’s drill could provide an additional powerful deterrent for many young people.”

Gavin Partington, director general at the British Soft Drinks Association, said sugar intake from soft drinks was already dropping. “Experience in the UK suggests that the action industry is taking – around reformulation, portion size and switching advertising spend to low/no calorie products – is having ample effect in changing consumer behaviour,” he said.

“In fact, sugar intake from soft drinks in the UK has fallen by almost 19% since 2013 – five times as much as other categories according to latest PHE data – and no- and low-calorie beverages now account for the largest category in the UK soft drinks sector.”