Soda drinkers beware?

Study links soft drinks to esophageal cancer

By S. Jhoanna Robledo
Special to MSN

Fran Bozdech, a 59-year-old high-school counselor in Larkspur, Calif., counts soda as one of her favorite beverages. Everyday, she pops a can of Diet Coke at lunch, and later in the evening, usually has another one during dinner. "I've probably been drinking Diet Coke as long as it's been available," she says.

Bozdech says she considers the soda routine a far-from-harmful habit. But is it?

For years, carbonated soft drinks have gotten a bad rap from dentists who say most of them are sugar-laden and encourage the growth of cavities. Nutritionists have blamed sodas in part for the obesity problem in America, saying they're full of empty calories. Now a team of digestive-disease doctors at a hospital in India are once again taking the fizz out of the popular drinks, declaring in a recent study that sodas may also be linked to esophageal cancer. Given this recent finding, should you skip sodas for good?

No definitive conclusion
Not necessarily, says Dr. Philip Jaffe, a gastroenterologist who teaches at the University of Connecticut Health Center. "The study is intriguing, but like all epidemiological studies, it has its limitations," he says. The problem is one of association. In the study, researchers cited U.S. data that showed per capita consumption of carbonated drinks rose by more than 450 percent from 1974 to 2000, from 10.8 gallons on average to 49.2 gallons in 2000. During that same period, the incidence rates of esophageal cancer rose by more than 570 percent in white American men. While the two trends may be associated with each other, however, some outside experts say the connection is tenuous.

Some of the harshest criticism comes from the soft-drink industry.

"I don't think this study has any scientific merit," says Dr. Richard Adamson, vice president of scientific and technical affairs for the National Soft Drink Association, a trade group that promotes the industry. "They looked at numbers and didn't establish a causal link."

Adamson says that because study authors didn't dig further to see if those diagnosed with the cancer also drank the beverage, asserting that sodas may cause esophageal cancer is a considerable reach. According to Adamson, people also ate more pizzas over that time span; cell phone and computer use skyrocketed as well. And yet, he points out, researchers didn't correlate those behaviors with esophageal cancer.

Link between GERD and esophageal cancer
On the other hand, GI doctors are aware that carbonated beverages like sodas can exacerbate gastroesophageal reflux disease (better known by its acronym GERD), which has been linked to esophageal cancer. The drinks can distend the top part of the stomach, which in turn relaxes the lower esophageal sphincter, a band of muscles that acts as a gatekeeper between the esophagus and the stomach. The LES normally remains shut; when left open, stomach acid can back up the swallowing tube, causing the burning sensation we call heartburn. In severe cases, the acid reflux can cause damage to the lining of the esophagus in a condition known as Barrett's esophagus; in a small number of these patients, Barrett's esophagus progresses to become a cancer.

In spite of the link between acid reflux and esophageal cancer, though, gastroenterologists say there's really no reason to go cold turkey and ditch sodas. After all, esophageal cancer, while deadly, is extremely rare; it affects approximately 15,000 Americans each year, accounting for just a small fraction of the more than 1.3 million cancer cases diagnosed annually. Plus, many other factors determine whether you'll suffer from GERD, including diet, the structure of the LES and genetics. "If you have serious acid-reflux disease and soda bothers you, then by all means avoid it," says Jaffe. But if you find that you tolerate it well, however, he says he sees no need to forgo it.

The bottom line? "Don't take the news about soda and esophageal cancer to heart," says Jaffe, who gave precisely that advice to a patient who swore he was going to give up the fizzy brew after hearing about the research from India. "If part of what makes life enjoyable for you is having a couple of Diet Cokes, then go ahead. Life is short and there are worse habits to have. You have to put everything into perspective."

That's just fine for Bozdech, who also suffers reflux symptoms now and then. "I wouldn't cut it from my diet unless there's more evidence," she says.

S. Jhoanna Robledo is a freelance health writer based in New York