Reality intrudes on diet soda health scare hype

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People who drink diet sodas may think that skipping the extra calories from regular sodas gives them leeway to eat some extra dessert or a big steak dinner. Not so, says a new study published in the American Journal of Clinical Nutrition. People who drink diet sodas but eat a less healthful overall diet are more likely to develop metabolic syndrome, researchers find. However, those who eat a more healthful diet and drink diet sodas do not have a notably higher level of this risk factor than those who drink no soda whatsoever.

Metabolic syndrome takes into account factors such as abdominal fat, elevated blood sugar, low HDL (good) cholesterol, and high blood pressure. In an effort to study the relationship between this syndrome and dietary factors, researchers from the University of North Carolina at Chapel Hill analyzed two groups of young adults with qualitatively different diets. About 1,700 participants fell into the prudent diet category, eating more fruits, vegetables, fish, whole grains, milk, and nuts, while approximately 2,300 fit in the Western diet category, eating meats, sugars, and fried foods. Looking at the participants diet soda consumption, the researchers found that about 32 percent of the diet soda drinkers eating a Western diet developed metabolic condition, whereas only 20 percent of diet soda drinkers who consumed a so-called prudent diet had this condition. The participants who did not drink any soda at all and had a more healthful diet were slightly less likely to have metabolic condition; within this group the rate was about 18 percent.

While some researchers have conjectured that diet sodas might increase health risk factors, one study author, Dr. Kiyah Duffey, points out that this new research suggests that it s really the dietary pattern that s driving this association with health. She adds that it s not necessarily the diet beverage that is the problem.

The study results came as no surprise to ACSH's Dr. Ruth Kava. These researchers have finally shown that the whole diet, not just what kind of soda a person drinks, is important, she observes. People who drink diet sodas but eat a Western diet may overindulge, and then drink diet soda to make up for dietary indiscretions. Clearly, that s not a way to maintain a healthy weight.

ACSH's Dr. Gilbert Ross couldn t agree more. When researchers see that people who drink diet sodas are more likely to be overweight, and then decide that drinking diet sodas makes them heavy, they are committing a classic epidemiological error, he says. What they are ignoring is the fact that people who drink diet sodas are making an effort to restrict their calories, meaning that they very likely have other risk factors, such as an otherwise high-calorie diet, that disposes them to a heavier weight.