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Doctors weigh in against the soda tax

January 27, 2010 |  2:01 pm

Back in September, we blogged about a well-meaning but misguided policy report in the New England Journal of Medicine that called for taxing sodas and other sugary drinks in the name of fighting obesity. As we wrote then:

It certainly stands to reason that switching from Coke to Diet Coke – or better yet, to water – would cause people to lose weight. Surprisingly, this connection is difficult for researchers to make. In some studies, people who knew they were saving calories on soda wiped out that advantage by taking extra helpings of food. Perhaps others saw less need to exercise. For whatever reason, cutting back on sugar-sweetened beverages is just not as good for the waistline as you’d expect.

Soda We critiqued the policy report for failing to cite any scientific evidence that a soda tax would have the desired effect of reducing the cumulative weight of Americans. (For evidence that it won’t, check out this L.A. Times story.) To wit:

In their policy report, the soda tax advocates cite four long-term, randomized, case-control trials – the kinds of studies considered the gold standard in medical research. But these trials pretty much fail to show that drinking fewer sugary drinks leads to widespread weight loss. Consider:

  • A British study of 644 kids between the ages of 7 and 11 found that the ones who drank fewer carbonated beverages had lower BMIs after one year compared with kids who didn’t. But the difference in BMI wasn’t statistically significant. That means the difference could easily be explained by random chance. This study did find that kids who drank fewer sodas were slightly less likely to become obese.
  • A Brazilian study of 1,140 9- to 12-year-olds found that a program to discourage kids from drinking sugary drinks had no effect on overall BMIs. The only group with a statistically significant benefit was overweight girls.
  • A Boston study of 103 high schoolers found that those who consumed diet drinks for 25 weeks didn’t lose weight compared with kids who drank regular soda, though there was a statistically significant difference for the one-third of kids with the highest BMIs.
  • A Chilean study of 98 overweight children found that those who drank milk instead of sugary beverages didn’t have a statistically significant reduction in body fat, though there was a bona fide increase in lean mass.

In the latest issue of the New England Journal of Medicine, other readers offered their own critiques.

Dr. Michael G. Kaplan (no relation to the writer) of Maimonides Medical Center in Brooklyn also noticed that the clinical trials cited all failed to produce the hoped-for results:

Before assigning blame for the obesity epidemic, we should have clinical evidence that an intervention to reduce the consumption of sugar-sweetened beverages is effective in achieving this goal, is either more effective or additive to the effect of other proven dietary therapies, and will reduce the long-term propensity for obesity.

Dr. Michael Keane of Casey Hospital in Australia said the soda tax advocates are pursuing a noble goal but said such a paternalistic approach is unwarranted:

In attempting to restrict peoples’ liberty, the onus is on the authors to convincingly show that the vast majority of the population has no concept that consuming junk food (including soda) in excess has the potential for adverse health effects. Yet, their article includes data showing that a majority of people support a tax on health grounds, which undermines the argument that some sort of market failure has made it impossible for consumers to be aware of the dangers of drinking too much soda.

And Dr. Michael J. Rinaldi of the Sanger Heart and Vascular Institute questioned the fairness of singling out soda for punitive taxes.

If soda is taxed, should this tax also be applied to all "fast food," confections, or portion size? Why limit it to food? Should we not tax all behaviors linked to health care expenditures? Why not deter gun and motorcycle ownership or sedentary lifestyle through taxation?

No letters were printed in support of the soda tax.

However, the tax got a big endorsement this week from New York City Mayor Michael Bloomberg. Testifying to state legislators who are considering a penny-per-ounce tax on full-calorie sodas, Bloomberg called the tax “far-sighted.”

According to this account by FoodNavigator-USA.com, he went on:

Today, more than half the residents of New York City, and nearly 40 percent of our public school students, are overweight, many of them seriously so. That puts them dangerously on track to contracting diabetes, high blood pressure, heart disease, asthma, depression, and other serious health problems later in their lives.

It’s in the interest of us all to prevent that from happening now -- and the surest pathway to changing behavior is through the wallet.

Not to mention that the billions of dollars such a tax would raise would go a long way to closing local and state budget gaps.

Another statewide soda tax proposal went down in flames last year, after New York Gov. David Patterson first supported then withdrew his support for the controversial measure. But Patterson put it back on the table last week, according to this report in the Financial Times.

California legislators have also considered a soda tax as a public health measure. You can read about last fall’s hearing by the state Senate Select Committee on Obesity and Diabetes and the Senate Health Committee here.

-- Karen Kaplan

Photo: Would a tax prompt this consumer to switch to Diet Coke? Photo credit: Los Angeles Times

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