A 10 per cent sugary drink tax has cut down the purchase and consumption of sugary drinks by an average of 10 per cent in places it has been introduced, a major review has revealed.
Research by the University of Otago, Wellington, published in Obesity Reviews, combined evidence from places where the tax has been applied, including four cities in the US: Cleveland, Ohio; Portland, Maine; Berkeley, California; and Philadelphia, Pennsylvania. A regional tax was also studied in Catalonia, Spain, while the effects of country-wide taxes were studied in Chile, France and Mexico.
Lead author Andrea Teng said their research takes a new approach in combining multiple studies examining the real-world impact of sugary drink taxes on sales, purchases and dietary intake before and after taxes were imposed, or between taxed and untaxed settings.
"This new review presents compelling evidence that sugary drink taxes result in decreased sales, purchasing or dietary intake of taxed beverages. For a 10 per cent tax, sugary drink volumes declined by an average of 10 per cent," she said.
"It shows taxes on sugary drinks are an effective tool to reduce consumption, and we know from other research that the high consumption of sugary drinks increases the risk of obesity, diabetes and dental caries."
The research also found evidence that sugary drink consumption may contribute to heart disease, cancer and premature death, Teng said.
Some of the studies looked at the alternative drinks people consumed instead of sugary drinks after the tax was applied.
It found that, with a 10 per cent tax on sugary drinks, there was a 1.9 per cent increase on average in consuming alternative drinks, with water specifically seeing a 2.9 per cent increase.
Co-author Amanda Jones said all the individual studies in the review found a reduction in sugary drink consumption, but the impact in some settings were greater than others. She said applying tax by its sugar content, rather than as a percentage of price, appeared to be important in having a more favourable impact on its consumption.
Some of the reasons behind the varying degrees of impact in places where a sugar tax has been applied may be found in combination with a range of other factors, including: other obesity prevention policies, the public's awareness of the tax, industry responses, consumer preferences, border permeability, availability of alternative beverages, and sensitivity to price.
However, Ms Jones said some of the differences in the studies may also be attributed to "non-price mechanisms".
"For example, a tax may signal to the public the seriousness of the health concern associated with consuming a product," she said. "A tax can also prompt manufacturers to reformulate sugar levels downward, as seen in the UK, even before their tax was introduced in April 2018."
While some studies looked at the impact of sugary drink taxes through socio-economic factors, more research is needed in this area, the authors said.
The World Health Organisation recommends governments impose a 20 per cent tax on sugary drinks, saying the evidence for reduced consumption and meaningful health effects is strongest for this food category.
"It is probably inevitable that this type of tax, which is highly targeted at protecting child health, will need to be seriously considered by New Zealand politicians," Ms Teng said.