Researchers have used a "virtual supermarket" to show how a junk food tax would lead shoppers to make healthier choices. Image / Supplied
Researchers have used a "virtual supermarket" to show how a junk food tax would lead shoppers to make healthier choices. Image / Supplied
KEY POINTS:
A world-first New Zealand-led study used a virtual supermarket to test consumers' responses to different kinds of food taxes and subsidies.
Researchers analysed a total of 4258 grocery shops, and found that taxes on food high in saturated fat, sugar and salt lead to shoppers buying markedly less of thetaxed nutrients. They also improved the healthiness of the overall shopping basket.
'Substitution effects' of saturated fat and salt taxes resulted in people buying more fruit and vegetables and more sugar as a percentage of total energy.
Researchers have used a "virtual supermarket" to show how a junk food tax would lead shoppers to make healthier choices.
Their study suggested that taxes targeting certain unhealthy foods wouldn't just result in consumers buying fewer of these items – but also swapping them out for substitutes.
They say that combining several taxes into one "junk food tax" could improve the overall healthiness of all the food we bring to the checkout counter.
But the food and grocery lobby group has hit back against that idea, arguing that many foods were already taxed – and that bringing in more would pass on costs to families.
To date, no price policies the like of what the researchers were proposing have been introduced in New Zealand.
"Our results point to beneficial health effects from food taxes and subsidies," says the University of Auckland's Professor Cliona Ni Mhurchu. Photo / Supplied
The Government has ruled out any sugary drink tax for this term at least, instead favouring a stance of working together with food industries.
But Health Minister David Clark told the Herald he was interested in the research and had asked officials for advice around it.
In the study, published in major journal the Lancet, New Zealand and overseas researchers used a randomised controlled trial that also observed substitution effects – or where shoppers switched a taxed product for an untaxed one, like fizzy drink for juice.
"We wanted to see how taxes and subsidies affected the whole shopping basket, not just the targeted food," said lead author Dr Wilma Waterlander, who conducted the study as part of her post-doctorate at the University of Auckland, and who now works at the University of Amsterdam.
The study's 1038 participants were able to virtually walk around and select items from the shelves of a 3D computer simulation based on images from a real New Zealand supermarket.
They each completed up to five shops - 4258 in all.
Food prices across the board were randomly varied from shop to shop, so researchers could gather as much information as possible about how people respond to price fluctuations.
On top of these random tweaks, researchers added bigger price changes to simulate five different policies: a fruit and vegetable subsidy (20 per cent), sweetened beverage tax (20 per cent or 40 per cent), saturated fat tax ($2 or $4 per 100g saturated fat), a salt tax (2c or 4c per 100mg sodium), sugar tax (40c or 80c per 100g sugar).
A control condition had no tax or subsidy.
"It is almost impossible to set up a study like this in the real world – for example, you would need to introduce food taxes in some parts of New Zealand and not others," Waterlander said.
"Our virtual supermarket allowed us to test food taxes and subsidies in a highly controlled, but realistic environment."
Using established criteria, researchers classified each food item as "healthy" or "unhealthy", and then analysed the healthiness of the shopping baskets.
With no taxes or subsidies, two-thirds of food purchases were classified as healthy.
Taxes on food high in saturated fat, sugar and salt led to shoppers buying markedly less of the taxed nutrients (132g less saturated fat, 119g or about 28 teaspoons of sugar, and 11g salt respectively).
These three taxes also improved the healthiness of the overall shopping basket by 1.8 per cent, 1.1 per cent and 1.3 per cent respectively.
"While these changes may sound modest, seemingly modest shifts can sum up to big health impacts across the whole population and over the long-run," said Professor Cliona Ni Mhurchu, from the University of Auckland's Faculty of Medical and Health Science.
The sweetened beverage taxes did not significantly improve overall healthiness, possibly because sugary drinks make up only a small fraction of people's diet.
But the most comprehensive version tested, which included sweetened beverages, energy drinks and fruit juices, resulted in shoppers buying 170ml per week less of those drinks.
Researchers also identified some intriguing substitution effects.
Both saturated fat and salt taxes resulted in people buying more fruit and vegetables and more sugar as a percentage of total energy.
People bought more fruit and vegetable when produce was subsidised - a third of a kilogram per week - however the healthiness of their overall baskets was unchanged.
"Our results point to beneficial health effects from food taxes and subsidies," Ni Mhurchu said.
"But we also find evidence of substitution effects, suggesting a broad, combined 'junk food tax' might be the best at increasing the healthiness of the total shopping basket, rather than narrowly focused individual food taxes.
"It also highlights the need to carefully study substitution effects, because these could undermine the effects of pricing policies, for example if saturated fat is replaced with sugar or vice versa.
"In view of these findings, we recommend policy makers seriously consider options for a combined junk food tax, perhaps accompanied by a fruit and vegetable subsidy, and how it stacks up against other dietary interventions."
They say that combining several taxes into one "junk food tax" could improve the overall healthiness of all the food we bring to the checkout counter. Photo / File
The researchers point out that the way food manufacturers reformulate products in response to food taxes would likely enhance health gains.
"Combinations of tax and subsidy options, accompanied by codes of practice and regulation of the food industry [eg, to set maximum levels of hazardous nutrients, to improve nutrition labelling, and to constrain marketing] might yield the best improvements in population diets and mitigate potential unintended consequences," they wrote.
PUBLIC CAMPAIGNS 'NOT ENOUGH'
David Clark today re-iterated that the Government had been clear that it would not be introducing any new taxes.
Its efforts on tackling obesity included a $47m initiative led by Sport NZ to boost healthy eating and activity in schools, along with work to reduce sugar levels in processed food and drink, and steps to develop a better food labelling system.
"The Ministry of Health is also working to address the promotion of unhealthy foods to children and young people."
But Ni Mhurchu said it was known that public health campaigns targeting individuals weren't enough to curb the epidemic – one in three Kiwi adults were now considered obese – and that instead, healthy eating should be made the easy choice.
"There is mounting evidence that one of the best ways to do this is by making healthy foods more affordable, and unhealthy foods less affordable."
Mexico and Hungary have introduced junk food taxes, and a growing number of other jurisdictions, including France, Mexico, the UK and Ireland, Saudi Arabia, Portugal and multiple US cities have adopted soft drink taxes.
After the Mexican sweetened beverage tax was introduced, purchases of taxed drinks fell by 5.5 per cent in 2014 and 9.7 per cent in 2015.
But New Zealand Food and Grocery Council chief executive Katherine Rich pointed that here, people often forgot food was already taxed at 15 per cent – and more in some cases.
"More taxes on top of GST will push food prices even higher. Food tax hikes of the magnitude used in this study would be regressive," Rich said.
"They would push many daily and essential basic foods further out of the reach of people who can least afford them or at least leave them with less money in their pockets for other essentials."
Of the study itself, Rich argued the virtual supermarket used didn't come close to reflecting real-life supermarket shopping.
"It's an artificial scenario which the writers are assuming is the same as supermarket shopping," she said.
"Shopping in a supermarket with real products and making decisions that cost real money is not the same as clicking a mouse and making pretend purchases in a computer programme.
"It's hardly surprising that most people in a simulation would think twice about a product with a price tag reflecting the taxes they have used – 20 per cent, 40 per cent, $2/100g of fat, or $4/100g of fat – because that's the natural thing to do, and many would shy away from them altogether."
