Harvard Health Blog
Sometimes it seems like people trying to choose a healthy diet and watch their weight can't catch a break.
Past studies have linked the consumption of sugar-sweetened drinks with cardiovascular disease, high blood pressure, and obesity. So it's easy to understand the appeal of diet soft drinks and other artificially sweetened beverages. If you drink two cans of Coke per day, switching to diet sodas could reduce your calorie intake by 8,400 calories each month. As long as you don't add in new sources of calories, over time that could add up to some serious loss of excess weight.
Can diet beverages really be bad for your brain?
Researchers analyzed health data from nearly 3,000 adults who had filled out diet surveys, and determined their incidence of stroke or dementia over 10 years. The findings were alarming.
Compared with people who said they didn't consume diet drinks, those who had at least one per day suffered three times more strokes, and were three times more likely to develop dementia. Consumption of regular (non-diet) soft drinks was not linked to a higher risk of these brain problems. And the results were unchanged when accounting for other important factors such as gender, diet, smoking, and physical activity.
Of course, there's more to the story
Before you despair or give up your favorite diet beverage forever, keep in mind that a study of this sort has some major limitations that can lead to faulty conclusions. For example:
--It's impossible to account for every factor that could affect the results. For example, maybe people with diabetes or a family history of diabetes chose sugar-free soft drinks more often than people without diabetes would. So it could be their diabetes and family history, not the diet soft drink consumption, that was responsible for their higher rates of stroke and dementia.
--This type of study cannot establish cause and effect. Even if there is a higher rate of brain disease in people who drink more diet soft drinks, we can't be sure that the diet soft drinks were the cause.
--This study did not look at the overall health effects of diet soft drinks; it's possible they are still a healthier choice than sugar-sweetened beverages.
--This study was conducted when most artificially sweetened beverages contained saccharin (Sweet'N Low, Sweet Twin), acesulfame-K (Sunett, Sweet One), or aspartame (NutraSweet, Equal). Newer sweeteners, such as sucralose (as in Splenda) were unlikely to have been included.
--While the risk of stroke or dementia was higher among those consuming diet soft drinks, only about 3 percent of the studied population had strokes and about 5% developed dementia. So, while a higher risk was observed among diet beverage drinkers, the overall risk in those who did or did not drink diet beverages was relatively low.
--This study only looked at artificially sweetened soft drinks. It didn't look at use of artificial sweeteners in foods or beverages other than soft drinks.
To understand how concerned we should be and how artificial sweeteners might cause these health problem (or others), additional research will be needed.
In the meantime...
I have to admit, this study has made me rethink my own habits. Would it be better if I started adding sugar to my coffee rather than my current routine of adding sucralose? I'm not sure. And this study gives me no guidance.
But if you drink a lot of diet soft drinks, this study should give you pause -- maybe moderation is in order. Or maybe drinking plain water wouldn't be such a bad idea.
(Robert H. Shmerling, M.D., is faculty editor of Harvard Health Publications.)
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