AP Photo/David Goldman

Consumption of sugar-sweetened drinks dipped 21 percent after a tax was enacted, a new study finds.

Consumption of sugary drinks has slid by 21 percent in Berkeley since a one-cent-per-ounce tariff was imposed on sweetened beverages, according to a study published today in the American Journal of Public Health.

The tax sailed through in a landslide vote in November 2014 and went into effect the following March. Proponents pointed to sugar as a culprit in chronic conditions such as obesity and diabetes. Intervening to curb consumption, they argued, would lead to a public health windfall.  

This new study, the authors write, is the first to evaluate whether or not folks did shun sugary drinks. To gauge residents’ drinking patterns, researchers from UC Berkeley and UC San Francisco conducted two rounds of in-person surveys of approximately 2,500 people aged between ages 18 and 94. The first surveys were performed between April and July 2014, when the tax was still a proposal. Follow-up surveys were conducted between April and August 2015, after taxation began.

Since poor, minority populations are most acutely impacted by grocery taxes, researchers positioned themselves to intercept foot traffic in low-income areas with high proportions of black and Hispanic residents, based on 2010 census tract data. Participants were asked to describe what sorts of drinks they consumed, and in what quantities.

After the tax was imposed, soda intake decreased by 26 percent, and consumption of sports drinks dipped by 36 percent, the researchers found.

And when they rebuffed sugar-sweetened sodas and juices, Berkeley residents turned to the tap; the researchers reported a 63 percent increase in water consumption. “Not only was the drop in sugary drink consumption in Berkeley greater than we expected, the apparent shift to less harmful products like water is a very good sign,” Kristine Madsen, a study author and associate professor of public health at UC Berkeley said in a statement.

The study measured how often participants drank sugar-sweetened beverages and water both before and after the beverage tax went into effect in Berkeley, as well as comparison cities of Oakland and San Francisco, which don’t tax sweetened drinks. (American Journal of Public Health)

The authors couch their findings with a number of caveats. It’s unclear, for instance, whether the tax itself was the main deterrent for consumers who changed their buying habits; it’s possible that the awareness about the health benefits of avoiding sugary drinks actually propelled that choice. Still, it’s worth noting that the nearby cities of San Francisco and Oakland—which voted against similar taxes—saw a 4 percent uptick in consumption over the same period.

While the tax is collected from distributors, the researchers noted in previous work that store owners passed that price hike on to consumers. By November 2015, the cost of soda in Berkeley had crept up by 0.69 cents per ounce, compared to the price in Oakland and San Francisco. Sometimes, as I’ve previously reported, grocery taxes spur residents to take their business elsewhere, to places where the taxes are lower. In this new study, the researchers controlled for that variable, and found that only 2 percent of Berkeley residents surveyed shirked the tax by buying soda in neighboring areas that didn’t levy one.

The authors note that this is one case study, and there’s no guarantee that the results would hold steady elsewhere—though they do echo the downward trends also noted in cities that enacted similar measures in Mexico and France.

The research also offers a road map for future work that adopts a wider lens, especially as other cities continue to eye similar policies. Philadelphia, for instance, imposed a tax on sweetened drinks back in June—not as a way to chip away at the obesity epidemic, but primarily as a way to pad the city’s coffers for public programs. Oakland will put a beverage tax to a vote again this fall.

Berkeley’s tax is projected to net $1.5 million each year; the funds will be allotted to school nutrition programs and public health grants. “While Berkeley is just one small city, this is an important first step in identifying tools that can move the needle on population health,” Madsen said.

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