Other studies have linked sugar-sweetened soft drinks with heart disease — and not surprisingly, given that the drinks may promote diabetes and obesity. But the causal link between stroke risk and sugar-free beverages is puzzling, says lead author Adam Bernstein, M.D., research director of the Cleveland Clinic's Wellness Institute.

One possibility, he notes, may be that the additives in sodas are not as safe as have been assumed. While more research needs to be done, Bernstein says, "there has been some suggestion that caramel coloring could lead to inflammation, which perhaps then could trigger some type of disease."



The average American drinks massive amounts of sugary beverages, Bernstein says, with sugar-sweetened sodas accounting for most of it. "The numbers are staggering — upwards of 45 gallons per person per year," he says. "That's nearly a gallon per week per person."

Bernstein said his team used complex statistical models to estimate what would happen if people replaced their soda intake with coffee, and found that coffee drinking conferred a lower stroke risk, especially when compared with diet soda. Coffee contains chlorogenic acids, lignans and magnesium, which act as antioxidants and help regulate blood sugar.

Hannah Gardner, an epidemiologist at the University of Miami's Miller School of Medicine who has also found a link between diet soda consumption and stroke, said Bernstein's study was "very strong" due to its design and the large number of people it included.

But because studies so far have merely found associations between soda consumption and stroke, there is no way to show conclusively that drinking soda causes stroke, she cautioned.

"I think more studies on this need to be conducted," she says. "We need to figure out both in humans and in basic science models what may be going on."



Also of interest: AARP Health Record: A safe place to manage your family's health information. »



Michael Haederle is a freelance writer whose work has appeared in People, the New York Times and the Los Angeles Times.