Berkeley residents cut their consumption of sugar-sweetened beverages by half in the three years after passing a soda tax in 2014, according to a UC Berkeley study that is among the first to document a long-term change in drinking habits from a citywide levy.

The study, published Thursday in the American Journal of Public Health, comes as California legislators are considering multiple statewide measures to reduce consumption of sugary beverages, which have been linked to obesity and related chronic health problems like diabetes and heart disease.

The UC Berkeley researchers found that in the first year after Berkeley’s soda tax was enacted, sweetened beverage consumption dropped 21 percent. By 2017, it had fallen 52 percent. By comparison, the study said, beverage consumption held steady in Oakland and San Francisco from 2014 to 2017. Both those cities enacted soda taxes toward the end of the study period.

“The research certainly suggests that taxes continue to have huge potential as a public health tool,” said Dr. Kristine Madsen, senior author of the paper and faculty director of the Berkeley Food Institute in UC Berkeley’s School of Public Health. “This is a major success in Berkeley.”

Sodas and other sweetened beverages are the largest sources of sugar in American diets, according to the U.S. Centers for Disease Control and Prevention. Researchers said it will probably take a decade or more to show that soda taxes can lead to reduced obesity and related health problems, but evidence that people are drinking fewer beverages is a good start.

Berkeley was the first U.S. city to enact a so-called soda tax, which applies to all beverages with sugar added, including sodas, fruit juices, sports and energy drinks, and sweetened coffees and teas. Other cities, in California and elsewhere in the country, followed.

Last year, California legislators, under pressure from the American Beverage Association, reluctantly voted to ban all new city-based soda taxes until 2030. But this week Democratic lawmakers proposed a statewide fee on sugary drinks, along with measures that would prohibit sales of extra-large sodas, add warning labels on sweet beverage packaging, and ban soda displays near checkout counters.

The American Beverage Association has repeatedly resisted tax efforts. William Dermody, a spokesman for the trade group, said soda taxes are not a fair or productive way to limit sweet beverage consumption.

The beverage industry already is helping reduce consumption by selling more drinks with less or no sugar, he said, and some studies have found that Americans had begun drinking fewer sweet beverages before soda taxes went into effect.

“America’s beverage companies believe there is a better way to help people reduce the amount of sugar they get from beverages than a tax that hurts working families and small businesses hardest,” Dermody said in a statement.

Other critics, including some Republican lawmakers, have referred to soda taxes as tools of a “nanny state” that narrow consumer choice, but UC’s Madsen said that given the billions of dollars the beverage industry spends on advertising, “we have to find a way to level the playing field, and taxes are one way to do that.”

The UC Berkeley study collected consumption data in face-to-face surveys of people in diverse, primarily lower-income neighborhoods in Berkeley, Oakland and San Francisco. A baseline survey was done in 2014, before the Berkeley soda tax went into effect. Annual surveys were repeated in 2015, 2016 and 2017. In all, 1,513 people participated in Berkeley and 3,712 in Oakland and San Francisco.

Survey respondents reported drinking about 1.25 sugary beverages a day in 2014 in all three cities. By 2017, that number had fallen by about half in Berkeley, but stayed the same in Oakland and San Francisco. That means the drop in Berkeley was almost certainly due to the tax, and not a regional shift in drinking habits, Madsen said. Consumption in Berkeley fell for all types of sweetened beverages except energy drinks.

Over the same time period, water consumption increased by about 29 percent in Berkeley and did not change in the other cities.

Madsen said there are limitations to her group’s work, most notably that it relies on self-reported beverage consumption. And demographically, Berkeley is not necessarily representative of the rest of the country, so it’s not certain that results there would hold up in other communities.

But the results echo studies done in other parts of the world, including research in Mexico showing that sales of sweetened beverages fell 5 percent in the first year after a national soda tax was enacted and 10 percent in the second year. An earlier study of the Berkeley soda tax found that soda sales fell about 10 percent in the year after the levy was imposed, and that sales of bottled water increased 16 percent.

“The (UC Berkeley) findings suggest not only that sugar taxes work, but that they keep working over time,” said Dr. Lynn Silver, a senior adviser with the Public Health Institute in Oakland who was involved with the earlier Berkeley study but not the new one.

“At a minimum we would hope that the decline seen in the first year would be maintained,” she said. “This suggests that not only was it maintained but it increased. That’s very significant.”

Erin Allday is a San Francisco Chronicle staff writer. Email: eallday@sfchronicle.com