Sweet Risk?

A lifetime loss of two days

Like all consumers of diet soda, University of Pittsburgh Physicist Bernard L. Cohen had every reason to be worried by the Canadian animal studies last year. The results seemed to indicate that the saccharin in low-calorie drinks and other artificially sweetened products would increase the risk of human bladder cancer. But, as a longtime researcher, Cohen knew that experimental results can often be misleading--and sometimes misinterpreted.

Whipping out his pocket calculator, Cohen set out to compare the risk of continuing the consumption of diet soda with that of returning to ordinary high-calorie drinks. For starters, he writes in Science, he used projections made from the Canadian study. These showed that there would be 1,200 extra bladder cancers a year if each person in the U.S. drank one twelve-ounce diet drink per day for his entire life. Then Cohen divided the total number of cancers in the population by the total number of drinks. He multiplied the result by an average reduction of life expectancy due to cancer--of 20 years. In that way, he determined that the diet soda habit would reduce life expectancy by about nine seconds per drink (as opposed to about twelve minutes for every cigarette), or about two days over a lifetime.

Using life insurance statistics showing that for every pound of excess weight there is a loss in life expectancy of one month, Cohen went on to estimate the consequences of drinking cans or bottles of ordinary soda pop (which contain about 100 calories, v. no calories for the diet soda). The results of all these comparative calculations were decidedly in favor of the saccharin-spiked drinks. Says Cohen: "If all other things were unchanged, the substitution of diet for nondiet drinks would increase life expectancy by 100 times more than the cancer risk reduced it."

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