(Reuters Health) - A soda tax has continued to help reduce Mexico’s consumption of unhealthy beverages, researchers say.

Purchases of sugar-sweetened beverages were down nearly 10 percent in the second year of the tax, a new study shows.

“The tax is working” toward its objective, senior author Shu Wen Ng said in a phone interview.

Ng, a health economist and a professor at the University of North Carolina in Chapel Hill, and her team estimated that Mexicans bought 9.7 percent less sugary drinks in 2015 than they would have before the tax took effect.

In an effort to wean consumers off sugary drinks and reduce the epidemics of obesity and diabetes, Mexico imposed a peso-per-liter excise tax at the beginning of 2014.

Mexicans cut their purchases of soda and other sugar-sweetened beverages by 5.5 percent the first year that the tax was imposed, the study calculated.

Researchers used Nielsen survey data on store purchases for nearly 6,650 urban Mexican households and estimated beverage purchases after adjusting for inflation, population growth and seasonal differences.

The poorest households showed the biggest drops in purchases of taxed sugary beverages, an average decrease of nearly 12 percent over two years.

Dr. Kirsten Bibbins-Domingo, chair of the U.S. Preventive Services Task Force and a professor at the University of California, San Francisco, has also been studying the public health effects of Mexico’s soda tax.

She described the new study as “encouraging for many cities and countries around the world which are exploring ways to shift the rising tide of diabetes.”

Similar taxes have been levied in countries around the globe - from Colombia to France and South Africa, and in American cities, from Berkeley, California, to Philadelphia.

A 2016 study found that low-income Berkeley neighborhoods slashed sugar-sweetened beverage consumption by more than one-fifth after the Northern California city enacted the nation’s first soda tax.

“We thought the tax might be an important public health measure, and it turns out it is likely to be,” Bibbins-Domingo said in a phone interview after reviewing the new findings.

They contradict industry reports of a drop in the effect of the tax in its second year.

The International Council of Beverages Associations, which represents the soda industry, disputed the new study’s results in a prepared statement. “First and foremost, this study does not show any impact from the tax on the obesity rates in Mexico,” the statement says.

Ng responded: “The current obesity rates crept up over time. Trying to slow that down and reversing the trend also will take time.”

“To expect that one policy alone is going to be successful in one or two years is ludicrous,” she said.

“If the beverage industry doesn’t think the tax is actually working in terms of reducing consumption, why are they fighting it so much?” she asked.

An October report from the World Health Organization recommended taxing sugary drinks to lower consumption and to reduce obesity, diabetes and tooth decay.

Previous studies showed that 70 percent of Mexican adults and 30 percent of Mexican children were overweight or obese in 2012.

Mexicans get one-fifth of their calories from sugary drinks, and 14 percent of them have diabetes, according to a 2016 study conducted by Bibbins-Domingo.

Mexico’s soda tax is on course to prevent diabetes, heart attacks and strokes in more than 200,000 adults and to save nearly $1 billion in healthcare costs over a decade, her 2016 study found.