Many public health advocates and scientific researchers have suggested that increasing the tax consumers pay when purchasing soda would be an effective way to help stem the growing rate of obesity in America. Most vocal among them in recent years has been Kelly Brownell, Director of the Rudd Center for Food Policy and Obesity at Yale University.

In an October policy report published in the New England Journal Of Medicine, Brownell and six co-authors laid out the case for a federal tax on all sugar sweetened beverages. Based on four long-term, randomized, case-control trials, the authors argued that such a tax would significantly reduce the consumption of soda, lower health care costs, as well as generate revenue for government health programs.

But in a series of letters published in the latest issue of the NEJM, several experts poked holes in Brownell's policy report, suggesting that there is little scientific or economic evidence supporting the efficacy of soda taxes.

One letter written by Dr. Michael G. Kaplan from Maimonides Medical Center in Brooklyn, NY, for example, pointed out that reducing soda consumption doesn’t automatically lead to less obesity.
Discussing the studies Brownell et al. cited, Kaplan explained that “none of the…long-term, randomized, controlled trials cited in the article met their primary end points…Before assigning blame for the obesity epidemic, we should have clinical evidence that an intervention to reduce the consumption of sugar-sweetened beverages…will reduce the long-term propensity for obesity.”

Other experts criticized the rationale behind the soda tax proposal—the assumption that people are incapable of making decisions without government dictating to them what they should consume. Michael Keane from Casey Hospital in Australia pointed out that not only is such a tax "an anathema to modern ethics," but also that Brownell et al. argued that Americans are too stupid to manage their own health by citing statistics which show that Americans are in favor of the soda tax based on health concerns.

And as many critics have before, Michael J. Rinaldi, M.D. from the Sanger Heart and Vascular Institute in Charlotte, NC questioned why soda was singled out as the primary cause of obesity, since all high-calorie foods can be tied to obesity. "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? How parental should government be?"

Citation: Kaplan M. G., Keane M., Rinaldi M. J., 'Taxing Sugar-Sweetened Beverages', NEJM, January 2010, 362:368-369