Fizzy Soda, Esophageal Cancer: No Link
Carbonated Soft Drinks May Not Raise Risk
Jan. 4, 2006 -- Drinking carbonated soft drinks does not appear to increase the chances of developing esophageal cancer, and diet sodas just might help protect against the deadly disease, research from Yale University suggests.
Diet soda drinkers were less likely to develop a specific type of esophageal cancer (esophageal adenocarcinoma) than people who didn't drink sodas as often or didn't drink them at all, the study found.
But Yale epidemiologist Susan Mayne, PhD, who led the study team, tells WebMD that other factors, such as leading a healthier lifestyle, may explain the observed protective effect among diet soda drinkers.
"What we can say is that we did not see any evidence that carbonated beverages are contributing in any way to the epidemic of this cancer," she says.
Fastest Growing Cancer
Cancer of the esophagus is one of the fastest growing malignancies in the Western world. It is often fatal because it is rarely diagnosed until the disease has become fairly advanced.
Food that you swallow travels through the tube-like esophagus to reach the stomach.
A more than threefold increase in one type of cancer called esophageal adenocarcinoma within the past three decades has coincided with an equally large increase in soft drink consumption. This has led to speculation that the popularity of bubbly beverages may be at least partly to blame for the cancer rise. Gastroesophageal reflux disease (GERD) is a risk factor for this cancer and Barrett's esophagus, and sodas can contribute to heartburn symptoms and GERD.
In one of the first scientific studies to examine the theory, the Yale researchers compared soda drinking patterns among 1,095 patients with esophageal and related stomach cancers and 687 people without cancer.
They found that the people without cancer drank more soft drinks on average than people who developed cancer. Those who drank the most fizzy beverages were no more likely to have developed esophageal cancer than those who drank the least.
High consumption of diet, but not regular, carbonated soft drinks was associated with a significant reduction in esophageal adenocarcinoma, the cancer type that is on the rise.
"The theory that soft drinks could be causing this cancer was picked up by the media and widely disseminated," Mayne says. "However, there was no direct evidence to bear on this hypothesis until we initiated our analysis."
What's Causing the Increase
So what is to blame for the dramatic rise in esophageal adenocarcinomas? Mayne and colleagues are part of a larger, government-funded study seeking to answer the question.
The research suggests that the biggest contributing factor may be the rise in obesity, which, in turn, may be leading to a rise in gastroesophageal reflux disease, also known as GERD. Acid reflux disease is a recognized risk factor for esophageal cancer.
"The current thinking is that the most likely culprit is obesity and gastroesophageal reflux," says American Cancer Society spokesman Len Lichtenfeld, MD.
He points out that there has actually been a decline in the incidence in another type of esophageal cancer -- esophageal squamous cell disease -- within the past few years. Major risk factors for this cancer include smoking and heavy alcohol consumption.
"Fewer people are smoking and more are obese," he says. "This could certainly explain why one cancer is on the decline and the other is on the rise."
Lichtenfeld says the Yale study "reliably answers the question" about whether carbonated beverages increase the risk of esophageal cancer.
"The answer is no," he says. "And the findings also raise the intriguing possibility that there may be some protective benefit, at least for diet soft drinks."