Study linking diet soda, stroke 'flawed'

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A study linking diet soda to an increased risk for stroke presented at the American Stroke Association's 2011 International Stroke Conference earlier this week has attracted public outcry from health officials across the nation who feel the study findings are critically flawed.

“The findings are so speculative and preliminary at this point that they should be considered with extreme caution,” Beth Hubrich, MS, RD, of the Calorie Control Council, said in a press release.

Hubrich joins a chorus of criticism from the likes of Richard Besser, MD, chief health and medical editor at ABC News, and Walter Willett, MD, chair of the department of nutrition at Harvard School of Public Health. During a Feb. 10 segment that aired on Good Morning America, Besser and Willett voiced concerns about public fear that may arise in reaction to the findings.

“I think we have to interpret the findings about diet soda very carefully, in almost any first report, we shouldn't really change our behavior, because it could easily have occurred by chance,” Willett said.

Health officials are wary to endorse the study's conclusion that diet soda “may be associated with a greater risk of stroke, MI or vascular death than regular soda,” noting that the data have not been published in a scientific journal and therefore have not been subjected to typically rigorous peer review processes.

“There are a lot of factors that were not taken into consideration, so we can't really assume that there is a causal relationship between diet soda and stroke,” Jennifer K. Cleary, APN, C-NP, of the Lipid Disorders and Metabolic Syndrome Clinic at Northwestern Memorial Hospital in Chicago, told Clinical Advisor.

Although the researchers surveyed study participants about soda consumption at the beginning of the study, it does not appear that additional surveys were conducted during the nine-year follow-up period, Cleary pointed out. Also, the study did not take into account the type or brand of diet soda. This may be relevant as the chemical additives used for dyes and sweeteners may vary.

Other critics have pointed out that studies participants were older (69 years old on average); stroke is more common among men 55 years and older, as well as women aged 65 years and older.

Additional aspects of the study that raise concerns include the self-reported nature of soda intake data, the broad terms used to categorize soda consumption and the small sample size of participants who reported drinking soda daily (4.5%) — imprecision that makes it difficult to draw meaningful conclusions.

“[The researchers] didn't look at how much salt [participants] took in, they didn't look at what other foods they ate. Those things we know are associated with stroke and heart attack,” Besser said.

Cleary echoed these concerns, stating that people who choose to drink diet soda on a daily basis are probably not making the best diet choices. “They might also be consuming fast food and making other unhealthy lifestyle choices.”

Currently, the American Heart Association recommends using low calorie sweeteners in moderation, and regulatory agencies including the FDA vouch that products made with aspartame, sucrolose or saccharine are safe.

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