Higher Prices Can Slash Sales of Sugary Soda

Jason Block, MD, MPH, of Harvard, and colleagues reported that, when a price increase of $0.45 was implemented in the cafeteria at Brigham and Women's Hospital in Boston, MA, for regular sodas, sales of the drinks dropped by 26% (P<0.001).

An educational effort -- consisting of posters and flyers touting the health benefits of cutting out regular soda -- did not decrease sales, but the combination of education and the price increase resulted in a 36% drop in sales of regular sodas from baseline (P<0.001).  Overall sales in the cafeteria were not affected, however. 

These findings could have implications for proposed policies of taxing regular soft drinks to reduce consumption and raise money for public health purposes, Block and colleagues noted in their paper.

The results, however, should be confirmed at multiple centers and in varied populations, they wrote.

Block and his colleagues implemented a five-phase intervention:

1. Existing prices on regular and diet sodas and water were posted during the baseline period.
2. Prices of regular sodas were increased by $0.45, a 35% increase. The new prices were posted on the refrigerators.
3. Prices were returned to baseline levels during a washout period and posted.
4. Posters and flyers were placed at strategic locations in the cafeteria stating: "Lose up to 15 to 25 pounds in one year and decrease your risk of diabetes by 1/2. Just skip one regular soda per day. For zero calories, try diet soda or water."
5. The researchers continued the educational effort and reinstituted the price increase on regular sodas.

The baseline phase lasted two weeks, and every other phase lasted four weeks. At baseline, regular and diet soft drinks accounted for 11% and 10% of beverage sales in the cafeteria. There were declines in regular soft drink sales during both phases involving a price increase, both with and without the educational material posted in the cafeteria.

The educational phase -- without a price increase -- did not result in further reductions in sales.

However, combining the price increase with the educational effort resulted in an additional 17% reduction in sales compared with the washout period (during which prices were returned to baseline levels). Sales of diet sodas increased by 20% and 14%, respectively, during the two phases that involved price increases for regular sodas (P<0.05 for both).

There was a non-significant trend toward increased water sales during the study; coffee sales increased significantly from the washout period through the end of the study period (P<0.05 for all phases).

Customers did not buy more snacks or desserts to compensate for lower regular soda consumption. Total quantity sales and net monetary revenue of the cafeteria were not affected.

During the last three phases of the study, Block and his colleagues collected sales information from the cafeteria at Beth Israel Deaconess Hospital in Boston for comparison. There were no interventions at this site.

Sales of regular sodas did not change, but there were increases in coffee and water purchases, "suggesting perhaps some temporal trends in coffee or water consumption as an explanation for this finding in both sites," the researchers wrote.

Block J, et al "Point-of-purchase price and education intervention to reduce consumption of sugary soft drinks" Am J Public Health 2010; 100: 1427-1433.