Two new studies linking soft drinks - both regular and diet - to brain changes, stroke and dementia could make those who love the drinks to rethink their hydration choices.
The researchers found no association between the intake of sugar-sweetened drinks and the risk of stroke and dementia, although they caution that sugary beverages pose other harms to health.
Matthew Pase, Ph.D., a study co-author from the Department of Neurology at the Boston University School of Medicine in MA, and his colleagues published their findings today in the journal Stroke.
Exactly why diet drinks might be linked to these conditions isn't known, Pase added.
Still, even when the researchers excluded diabetics from the study, they found a link between drinking diet soda and the risk of dementia.
The results showed that adults who had one or more diet drink a day were 2.9 times more likely to develop dementia and 3 times more at risk of strokes compared to those who virtually none at all.
"When the authors controlled for hypertension and diabetes and obesity the effects diminish, which implies that some of the effects of artificially sweetened beverages could still be going through a vascular pathway", he said about the new study. Now just 38% of all soft drinks consumed are fully sugared, it said. "We recommend that people drink water on a regular basis instead of sugary or artificially sweetened beverages".
One stroke expert said the findings are far from definitive.
Pase and other researchers say the work points clearly to the need to investigate the possible biological reasons artificial sweeteners might affect the brain and the need for more experimental and clinical trials. She's an assistant scientist in the department of neurology at the University of Miami Miller School of Medicine.
Is there a healthy option? 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.
Both relied on data from the Framingham Heart Study, which began in MA in 1948 to identify the risk factors for heart disease and has been extended several times since.
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4,000 Framingham residents 30 or older were monitored for the study.
Three times over seven years, the researchers reviewed what people were drinking.
The researchers acknowledged several study limitations, including the observational nature of the data, the absence of ethnic minorities, and the use of a self-reported questionnaire to obtain dietary intake data, which may be subject to recall bias. The study examined beverage intake of 2,888 people over the age of 45 for its stroke analysis and 1,484 people over the age of 60 for the studys dementia analyses.
These findings appear separately in the journals Alzheimer's & Dementia and the journal Stroke.
The investigators adjusted their findings for risk factors such as age, sex, how much participants ate, education, diabetes and a genetic risk for Alzheimer's disease.
"In fact, based on the evidence, Public Health England is actively encouraging food and drink companies to use low-calorie sweeteners as an alternative to sugar and help people manage their weight".
"Beverages are an important consideration, and diet beverages provide safe, reduced calorie options that people can enjoy while working towards achieving their healthy lifestyle goals", Rankin added.
We need to be cautious in the interpretation of these results, said Rachel K. Johnson, Ph.D., past chair of the American Heart Associations Nutrition Committee and professor of nutrition at the University of Vermont.
In response, Lauren Kane, a spokeswoman for the American Beverage Association, issued a statement from the group that said low-calorie sweeteners found in beverages have been proven safe by worldwide government safety authorities. But they found other troubling signs.
A new study, however, suggests that this may not be the case.
However, they admitted that they can not prove a causal link between intake of diet drinks and development of either medical condition because their study was merely observational and based on details people provided in questionnaires logging their food and drink habits.