The Dutch data, published in Appetite, used a 3D computer simulation of a supermarket to examine how modifications o the price of sugar sweetened beverages (SSBs) impacted the purchase of beverages and snack using a randomised controlled design.
Led by Wilma Elzeline Waterlander of VU University Amsterdam the team found that participants in the price increase condition purchased significantly less SSBs than the control group.
What's more, the tax doesn’t have to be huge in order to be effective, said the team - who found that an increase from the standard 6% to 19% “was effective in decreasing sugar-sweetened beverage purchases, and had no significant effects on other beverage categories or snack foods.”
Waterlander and her team concluded that such an increase in VAT results in .90 litres less SSB purchases per household per week.
"For an average Dutch household (2.2 persons) this would result in a decrease of around 400 mL of SSB (168 kcal) per week," wrote the team.
"While this reduction in calorie intake is relatively modest, it could have substantial cumulative effects on the long term and, more importantly, could add up to a considerable impact at population level," they concluded.
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The research randomised 102 participants to purchase groceries on a single occasion at the three-dimensional 'virtual supermarket'. After being presented with a shopping budget appropriate to the size of their household, each participant entered the virtual shop and navigated through various aisles and selected products with a mouse click.
The trial contained two conditions: experimental condition with a 19% tax on SSBs (to reflect an increase in Dutch value added tax from 6% to 19%); and a control condition with regular prices.
After each participant had 'checked out', the team analysed the data from their purchases - focusing particularly on drinks and snack-food items.
After analysing all of the data from both arms of the trial, Waterlander and her team found that those participants shopping with the higher tax rates bought fewer sugary drinks: “Our study observed no change in purchases in other beverage categories as a consequence of the tax, except for an increase in coffee and tea purchases,” they said.
“It has been argued (particularly by the beverage industry) that alcohol consumption might increase as a consequence of a sugar-sweetened beverage tax," added the team. "We included alcoholic drinks in our analysis, and did not observe any significant changes as a consequence of the price increase of sugar-sweetened beverages.”
Waterlander and her colleagues also reported no significant increase in snack-food purchases.
Indeed, when faced with higher prices on soda, it was found that shoppers switched to a different (and healthier) beverage, but did not compensate for the loss of sugar by buying more snacks.
The team concluded that their data "strengthens the foundation for the introduction of SSB pricing policies", adding that the results are particularly promising "since moderate taxes are likely to be more feasible and politically acceptable than high taxes"
Published online ahead of print, doi: 10.1016/j.appet.2014.03.012
"Effects of a price increase on purchases of sugar sweetened beverages. Results from a randomized controlled trial"
Authors: Wilma Elzeline Waterlander, Cliona Ni Mhurchu, Ingrid H.M. Steenhuis