Worried about diet soda? Strokes are not likely.

diet cokeLate last week, the popular press began touting a paper by Matthew Pase and coworkers in the journal Stroke on the newfound risks of diet sodas, (artificially sweetened beverages, ASBs) as compared to sugar sweetened beverages (SSBs). Most of the articles have been pretty accurate, NBC, CNN and Arstechnica got it pretty much right. Only Meredith Bland, writing as Scary Mommy went a bit off the deep end.

What the researchers did was examine data on 2888 participants from the Framingham Heart Study Offspring Cohort, looking at their reported consumption of ASBs and SSBs, and the results of their regular examinations, which ended in 2001. Surveillance continued for 10 years, ending in 2011.

They found that “higher recent and cumulative consumption of ASBs were associated with an increased risk of ischemic stroke, all-cause dementia, and Alzheimer’s disease dementia.” Specifically, they found that stroke was 2.96 times as likely and dementia about 2.89 times as likely.

This sounds really worrisome, but bear in mind that this is a single study, and that they found a correlation, not any actual cause. In fact, they didn’t propose any cause, because these results are very difficult to explain medically. They do, of course, note that “future research is needed to replicate our findings and investigate the mechanisms…”

What many writers did not specifically mention, is that there is an accompanying editorial in this same journal by Wersching, Gardener and Sacco, that is quite critical of Pase’s paper. In addition to pointing out that they show correlation and not causation, the editorial notes that while Pase reported that those consuming SSBs did not seem to have strokes or dementia, they suggested that this could be because of selection bias because those consuming sugary beverages may have died earlier. They note that previous studies have indeed found negative outcomes from those consuming SSBs.

As regards those consuming diet beverages (ASBs), the editorial suggests that “reverse causation” cannot be ruled out. What they mean is that those who know they are at risk may have chosen to switch to diet beverages and thus their strokes and dementia were incorrectly being correlated with the diet beverages instead of their already existing risk. They specifically point out that “disentangling these effects” is “challenging” in such studies.

Finally, they note that there is no obvious biological pathway to explain these cardiovascular events in those consuming diet beverages. They suggest that the current body of research, including this paper, is inconclusive and that carefully designed studies, following subjects from childhood would be necessary to establish these effects for certain.

So, for the moment, it would seem that nothing has really been established concerning diet beverages, and you can go ahead and sip yours without new worries.




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