Sugar tax has cut consumption of sugary drinks — meta-analysis

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A 10% tax on sugary drinks has cut the purchase and consumption of sugary drinks by an average of 10% in places it has been introduced, a just published major review has found. Researchers from the University of Otago, Wellington, New Zealand, combined evidence from settings where a sugary drinks’ tax had been applied and evaluated it into a meta-analysis. Studies included four cities in the US: Cleveland, Ohio; Portland, Maine; Berkeley, California; and Philadelphia, Pennsylvania. A regional tax was studied in Catalonia, Spain, and the effects of country-wide taxes were studied in Chile, France and Mexico.

Lead author Dr Andrea Teng says the 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% tax, sugary drink volumes declined by an average of 10%. “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.”

Teng says there is also evidence that sugary drink consumption may contribute to heart disease, cancer and premature death.

Some of the studies looked at the alternative drinks people consumed instead of sugary drinks after the tax was applied. With a 10% tax on sugary drinks, there was a 1.9% increase on average in such alternative drinks, and for water specifically there was a 2.9% increase. This healthier substitution pattern is not conclusive, but in three out of the four settings where substitution occurred, the increase in consumption of the other non-sugary drinks was statistically significant.

A co-author of the review, Dr Amanda Jones, says all the individual studies in the review found a reduction in sugary drink consumption, but the impact in some settings was greater than others. Applying tax by thresholds of sugar content, rather than as a percentage of price, appeared to be important for determining a more favourable impact.

Other reasons for differences between settings may be the combination with 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. For example, Chile also decreased tax on low-sugar beverages at the same time as increasing the tax on high-sugar beverages; Mexico introduced a sugary drinks’ tax combined with a junk food tax; and France also taxed soft drinks with artificial sweeteners.

“Some of the differences found in these studies may also be due to non-price mechanisms. For example, a tax may signal to the public the seriousness of the health concern associated with consuming a product,” Jones says. “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.”

Some studies looked at the impact of sugary drink taxes by socio-economic factors, but more research is needed in this area, the authors say. In Mexico, for instance, there were greater consumption declines in lower income households, while the opposite was true in Chile.

The World Health Organisation recommends governments impose a 20% tax on sugary drinks, saying the evidence for reduced consumption and meaningful health effects is strongest for this food category.

Abstract
The aim was to conduct a systematic review of real‐world sugar‐sweetened beverage (SSB) tax evaluations and examine the overall impact on beverage purchases and dietary intake by meta‐analysis. Medline, EconLit, Google Scholar, and Scopus databases were searched up to June 2018. SSB tax evaluations from any formal jurisdiction from cities to national governments were eligible if there was a comparison between pre–post tax (n = 11) or taxed and untaxed jurisdiction(s) (n = 6). The consumption outcome comprised sales, purchasing, and intake (reported by volume, energy, or frequency). Taxed and untaxed beverage consumption outcomes were examined separately by meta‐analysis with adjustment for the size of each tax. The study was registered at PROSPERO (CRD42018100620). The equivalent of a 10% SSB tax was associated with an average decline in beverage purchases and dietary intake of 10.0% (95% CI: −5.0% to −14.7%, n = 17 studies, 6 jurisdictions) with considerable heterogeneity between results (I2 = 97%).The equivalent of a 10% SSB tax was also associated with a nonsignificant 1.9% increase in total untaxed beverage consumption (eg, water) (95% CI: −2.1% to 6.1%, n = 6 studies, 4 jurisdictions). Based on real‐world evaluations, SSB taxes introduced in jurisdictions around the world appear to have been effective in reducing SSB purchases and dietary intake.

Authors
Andrea M Teng, Amanda C Jones, Anja Mizdrak, Louise Signal, Murat Genç, Nick Wilson

University of Otago material
Obesity Reviews abstract


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