By Lisa Rapaport

(Reuters Health) – People in Berkeley, California, dramatically cut their soda consumption after the city implemented a “soda tax,” a new study suggests.

Three years after Berkeley passed its soda tax in November 2014, residents reported drinking half as many servings of sugary drinks as they did before the tax, the study found. Over the same three-year period, water consumption surged 29 percent.

“We know from experience with tobacco and alcohol taxes that people are sensitive to changes in price, so we expect that taxes will reduce consumption of taxed products,” said senior study author Dr. Kristine Madsen of the University of California, Berkeley.

The study is the first to document the long-term impacts of a soda tax on drinking habits in the United States. It shows that soda taxes can encourage healthier drinking habits, potentially reducing sugar-linked diseases like diabetes, heart disease and tooth decay, Madsen’s team writes in the American Journal of Public Health.

The results come at a critical time for other cities considering soda taxes. A number of cities, including Philadelphia and Seattle, now have soda taxes on the books. But both California and Washington state passed bills in 2018 that ban municipalities from implementing soda taxes.

In Berkeley, 76 percent of voters were in favor of levying a penny-per-ounce tax on all sugar-sweetened beverages. The tax is levied on distributors, rather than directly on consumers, but previous research suggests that retailers have raised prices in response to the tax.

The bulk of Berkeley’s soda tax revenue is dedicated to supporting nutrition education and gardening programs in schools and to local organizations working to encourage healthier behaviors in the community.

To find out about residents’ drinking habits, the team polls around 2,500 people each year in high foot traffic intersections in racially and demographically diverse neighborhoods across Berkeley, Oakland and San Francisco.

Surveys revealed a steep drop in sugar-sweetened beverage consumption in Berkeley between 2014 and 2017 for sugary drinks overall as well as for sodas like Coke and Pepsi, sports drinks like Gatorade and Powerade, and sweetened teas and coffees.

Residents of neighboring Oakland and San Francisco drank about the same number of sugary beverages in 2017 as they did in 2014, the surveys found. This suggests that changes in drinking habits were unique to Berkeley and not signs of a regional trend in drinking habits unrelated to the tax, researchers conclude.

“This just drives home the message that soda taxes work,” Madsen said. “Importantly, our evidence comes from low-income and diverse neighborhoods, which have the highest burden of diabetes and cardiovascular disease, not to mention a higher prevalence of advertising promoting unhealthy diets.”

Oakland and San Francisco have since enacted their own soda taxes, which went into effect in mid-2017 and 2018, respectively.

One limitation of the study is that the surveys were not a random sample of all residents, the study authors note. Berkeley is also a relatively small and highly-educated city, and results from a soda tax here may not represent what would happen elsewhere.

But the results do suggest price hikes can help motivate consumers to change their unhealthy habits, said Christina Roberto, a researcher at the Perelman School of Medicine at the University of Pennsylvania in Philadelphia who wasn’t involved in the study.

“Economic theory says that when you raise the price of a good, people should buy less of it, and that is a reliable, predictable finding,” Roberto said by email.

“Most people want to live a long, healthy life and want support in doing that,” Roberto added. “Taxes are a way to encourage healthier beverage choices and the money people don’t spend on sugary beverages can be saved or spent on other items.”

SOURCE: American Journal of Public Health, online February 21, 2019.