EXPERT REACTION: Artificially sweetened soft drinks linked to higher risk of stroke and dementia
Organisation/s: Swinburne University of Technology
These comments have been collated by the Science Media Centre to provide a variety of expert perspectives on this issue. Feel free to use these quotes in your stories. Views expressed are the personal opinions of the experts named. They do not represent the views of the SMC or any other organisation unless specifically stated.
Dr Mary Hannon-Fletcher is Head of Health Sciences at Ulster University, UK
This is good quality research on the one hand. Using Food Frequency Questionnaires has its limitations, especially when the participants are asked to report on their eating/drinking habits over the last year. How accurate could you be?? So this approach is easy but will not provide definitive answers. On average those who drink more will show up against those who drink far fewer sugary drinks. On the other hand, participants will sometimes say what you want to hear and even lie; this population is very well researched and as such are biased, in my view.
These data are sound as far as they go. However it is important to note ‘the associations between recent and higher cumulative intake of artificially sweetened soft drinks and dementia were no longer significant after additional adjustment for vascular risk factors and diabetes mellitus’ – as the editor also pointed out. So are the conclusions sound? Perhaps not!
There is little conclusive existing evidence on this subject, however others have reported a link between SSB consumption and stroke and the direct causal pathways linking SSB and vascular outcome which is why both the World Health Organisation and American Heart Association / American Stroke Association are actively engaged in campaigns to reduce the intakes of SSBs.
The authors cannot say that the effect they report is causal, as the tool they have used cannot draw a causal link. It will need further investigation, perhaps starting in childhood.
The authors tried to account for confounders, but I agree with the editor: the intake of SSBs was not associated with stroke or dementia. This finding could be attributed to selection bias, such that particularly vulnerable participants - long-term SSB consumers with a very high cardiovascular risk - died earlier. This could also explain the lower-risk profile of high SSB consumers compared with high ASB consumers, the data of which were collected in 1998 to 2001.
We should not drink too many sweet drinks no matter how they are sweetened. Both are bad for our health in the long run.
Prof Naveed Sattar is Professor of Metabolic Medicine at the University of Glasgow, UK
This is an interesting paper but I would strongly caution against the conclusion that artificially sweetened drinks may increase the risk of stroke and Alzheimer’s.
It is only one study and relatively small at that - there is little other strong evidence to support a link between artificially sweetened drinks and adverse health outcomes.
It’s an observational study, so the authors of this study could not be certain that people who are developing ill health switch to artificially sweetened drinks in preference to sugary ones. This is a phenomenon called reverse causality whereby some apparent health behaviours are the result of ill health rather than the cause. The same sort of finding is true for alcohol; when folk become sick, they tend to stop or cut alcohol beverages. The study could also be subject to residual confounding so unmeasured factors and not the different drink types are the true reasons for associations.
Hence, on a personal note, I remain very happy to drink diet drinks rather than sugar-rich drinks since the latter clearly both harm teeth and are a source of lots of refined sugar. Those are facts.
We already know that sugar-sweetened drinks are associated with increased risk of diabetes, hypertension, stroke and coronary artery disease. However, there is still uncertainty about any link between artificially sweetened drinks, which are often used as an alternative to sugar-sweetened drinks, and cardiovascular disease or dementia. The research claims to show an association between artificially sweetened drinks and stroke and dementia, whereas no similar association was seen for sugar-sweetened drinks.
This is an observational study, where it is very hard to control for all the possible confounders. Moreover, this population is neither ethnically diverse nor necessarily representative of the USA or other countries. The researchers relied upon self-reported data about drinks and diet which may be biased.
Crucially, the association with stroke and dementia disappeared after adjusting for diabetes and vascular risk factors, such as high blood pressure and prior heart attack. In other words, individuals who drank a lot of artificially sweetened beverages already had cardiovascular risk factors which explained their risk of dementia or stroke, rather than the drinks per se.
There is no evidence that artificially sweetened drinks cause stroke or dementia on the basis of this analysis. However, we also cannot assume that they are good for your health as a substitute for sugar-sweetened drinks, and so they should be used in moderation.
Although interesting, this paper does not tell us that artificially sweetened drinks cause stroke or dementia. The statistical relationship between artificially sweetened drinks and dementia disappears when the analysis controls for diabetes. This makes it more likely that there is a group of people who both use artificially sweetened drinks and are at higher risk of dementia, presumably because they have a risk factor, such as diabetes, for which a low sugar diet has been recommended.
While the stroke effect remains even after diabetes has been taken into account, we should bear in mind that this is just one study with relatively small subgroups of participants. There is still strong evidence that high sugar intake is bad for general health. Nevertheless, it is good to question our assumptions about replacing sugar and future research could clarify the relationship between artificially sweetened drinks and neurological disease.
As people are becoming more aware of the consequences of a high-sugar diet, many are turning to artificially-sweetened diet fizzy drinks as an alternative to those with lots of sugar. This interesting new study has pointed to higher rates of dementia in people who drink more artificially-sweetened drinks, but it doesn’t show that these drinks are the cause of this altered risk. When the researchers accounted for other risk factors for Alzheimer’s, such as risk genes, diabetes, heart disease, cholesterol levels and weight, this significant association was lost suggesting that these drinks are not the whole story.
Future studies will need to confirm these findings in other groups of people, and explore what might be underlying any link between artificially-sweetened soft drinks and dementia. The best current evidence suggests that when it comes to reducing your risk of dementia, what is good for your heart is also good for your head. Eating a healthy balanced diet, keeping physically and mentally active, not smoking, drinking in moderation, maintaining a healthy weight and keeping cholesterol and blood pressure in check are all good ways to support healthy brain ageing.
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