Ask the Doctors

Dear Doctor: A recent news report said that diet sodas may be tied to stroke or dementia risk, but it didn't provide a possible cause. What's your take?

Dear Reader: You're referring to a 2017 study published in the journal Stroke. The study followed two groups of people: one over age 45 (2,888 people) and one over age 60 (1,484 people). The participants filled out food questionnaires three times: between 1991 and 1995, between 1995 and 1998, and between 1998 and 2001. Participants were asked about the type and frequency of their beverage intake. The groups of beverages included sugar-sweetened soft drinks, fruit juice, sugar-sweetened fruit drinks and artificially sweetened soft drinks. After the last questionnaire, researchers assessed the rates of stroke and dementia in the subsequent 10-year period.

People who drank artificially sweetened soft drinks one to six times per week had a 59 percent increased risk of stroke compared to those who did not drink artificially sweetened soft drinks. This rate increased to 79 percent among people who drank one or more of these drinks per day. The rate was even higher among people who reported this higher use most recently (between the years 1998 and 2001).

In regards to dementia, people who drank artificially sweetened soft drinks one to six times per week had a 30 percent increased risk of dementia compared to those who drank no artificially sweetened soft drinks, while people who drank one or more per day had a 70 percent increased risk.

These numbers seem significant, but the study's many confounding factors decrease their strength. For one, the number of people suffering strokes or developing dementia was limited, making it difficult to draw overarching conclusions.

Also, consider that -- according to the data -- people who drank sugar-sweetened soft drinks more than three times per week actually had a 20 percent reduction in the risk of strokes compared with those who drank none -- and a 23 percent decreased risk of dementia. My kids might disagree, but I really don't think that a greater number of sugar-sweetened soft drinks would be good for you.

Further, even before the study began, 22 percent of those who drank artificially sweetened sodas had diabetes, while 7 percent who didn't drink them had diabetes. Diabetes itself is a risk factor for both stroke and dementia, so the increased risk found in the study may have nothing to do with the sodas. The authors said they adjusted for this, but with such small numbers, that's difficult to do.

Don't get me wrong: Artificially sweetened sodas are certainly not healthy. They trick the brain and the body into believing it has had something sweet and thus may cause a greater overall craving for sweet foods or drinks. A 2012 evaluation of two large studies with 127,456 people found a 12 percent increased risk of stroke among people who drank one or more sugar drinks per day -- and a 9 percent increased risk of stroke among people who drank one or more artificially sweetened drinks per day. These results were more significant than the current study due to the large population of people involved.

So while there may be a link between diet sodas and stroke, it doesn't seem to be to the degree that this news report suggested.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)

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