The researchers warn that diet soft drink consumers might differ from other groups because they may engage in other unmeasured healthy behaviors. The study is published in the January 4 issue of Journal of the National Cancer Institute (JNCI).

It was hypothesized by others that carbonated soft drinks might have contributed to the development of adenocarcinoma of the esophagus. The theory was based on factors including similar time trends; acidic carbonated soft drinks causing gastric distension that might affect the lower esophagus; and association of carbonated soft drinks with heartburn at night, a known risk factor for esophageal adenocarcinoma.

"The theory that soft drinks could be causing this cancer was picked up by the media and widely disseminated," said lead author of the Yale study Susan Mayne, professor in the Department of Epidemiology and Public Health at Yale School of Medicine and associate director of the Yale Cancer Center. "However, there was no direct evidence to bear on this hypothesis, until we initiated our analysis."

Potential causes of esophageal adenocarcinoma were identified by Mayne and her colleagues in a previously completed population-based, multi-center study of 1,095 cancer patients and 687 control subjects. As part of that study, they conducted a full dietary interview and had access to available data on consumption of both regular and diet soft drinks.

"Our team analyzed that data as the first direct test of the hypothesis that soft drinks might have contributed to the increase in this cancer," said Mayne. "We found that contrary to the hypothesis put forth by other researchers, carbonated soft drink consumption was inversely associated with esophageal adenocarcinoma risk, mainly attributable to diet soda, and that high intake did not increase risk of any esophageal or gastric cancer subtype in men or women."

Other Yale authors on the study included Harvey Risch, principal investigator of the grant that supported the work, Robert Dubrow, and Mayne's former student, Lauren Borchardt. Authors from other centers included Wong-Ho Chow, Marilie D. Gammon, Thomas L. Vaughan, Janet B. Schoenberg, Janet L. Stanford, A. Brian West, Heidi Rotterdam, William J. Blot and Joseph F. Fraumeni, Jr.

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