long-term observational study has shown that drinking one or more artificially sweetened beverages on a daily basis is linked to almost three times the risk of developing stroke or dementia compared to those who drank them less than once a week. However, claims that the observational study includes a number of limitations have come to light, with the ISA stating the study “provides no convincing evidence and no plausible mechanism for a causal relationship between diet drinks’ consumption and health indices, in this case stroke and dementia.”

The research was based on data from the Framingham Heart Study Offspring Cohort and looked at 2,888 primarily Caucasian people over the age of 45 for the stroke study and 1,484 people over the age of 60 for the dementia part of the study. 

Researchers reviewed what people were drinking at different times over a period of seven years, based on food frequency questionnaires filled in by the study subjects. They then tracked the study subjects for ten years to establish who developed stroke or dementia, and compared the data on eating and drinking habits to the risk of developing stroke and dementia over the course of the study.

Among the study participants tracked during the study, there were 97 cases (3 percent) of stroke, 82 of which were ischemic (caused by blockage of blood vessels), and 81 (5 percent) cases of dementia, 63 of which were diagnosed as Alzheimer’s disease.

Used statistical models adjusted for various risk factors, researchers found that people who drank at least one artificially-sweetened beverage a day were three times as likely to develop ischemic stroke and 2.9 times as likely to develop Alzheimers disease dementia. The data collected did not distinguish between the types of artificial sweeteners used in the beverages.

However, a release from the ISA has stated that the research is “yet another observational study providing no convincing evidence and no plausible mechanism for a causal relationship between diet drinks’ consumption and health indices, in this case stroke and dementia.”

“The findings of that study, in fact, are based only on a small group of 97 cases of incident stroke and 81 cases of dementia out of a total of 2888 participants aged over 45 and 1484 participants over 60 who were included in the analysis for incident stroke and dementia, respectively.”

“Given such small numbers, consumption of low-calorie sweetened beverages could be divided into 3 levels only, i.e. non users, occasional (less than daily) and regular users (one or more beverage per day).”

“The latter category included 519 subjects only. This translates into less than two-dozen cases of stroke or dementia among regular low-calorie sweetened beverage users. In addition, there was no convincing trend in risk, i.e. the hazard ratio of ischemic stroke was already about 2-fold elevated among occasional low-calorie sweetened beverage users.”

Professor Carlo La Vecchia from the University of Milan, Italy, also noted the limitations of the study, saying, “The association between diet drinks and stroke is less strong in the third statistical model, which adjusted for additional cardiometabolic variables that may be associated with an increased risk of stroke.”

“Thus, under-adjustment is possible, i.e. more accurate and/or valid measurement of blood pressure and other covariates may lead to less strong association. With regard to dementia, in the more complete model 3, there is no significant association with diet drinks’ consumption.”

The study’s authors noted that the main limitation of the research was that it only shows a trend among one group of people and was not designed, or able, to prove cause and effect.

Rachel K. Johnson, PhD, MPH, RD, past chair of the American Heart Association’s Nutrition Committee and professor of nutrition at the University of Vermont said that limiting added sugars is an important strategy to support good nutrition and healthy body weights, but warned that until more is known, people should use artificially sweetened drinks cautiously.

“They may have a role for people with diabetes and in weight loss, but we encourage people to drink water, low-fat milk or other beverages without added sweeteners,” she said.

Within its statement, the ISA added that there is an established and strong bank of scientific evidence from clinical studies demonstrating that low calorie sweeteners and diet drinks containing them can be a useful tool in sugar and energy reduction, when used in place of sugar.

“At a time when obesity (a major risk factor for cardiovascular diseases including stroke) and diabetes rates (a known risk factor for dementia) continue to increase worldwide, it would be unfortunate and dangerous from a public health perspective if people were to be discouraged from using low calorie sweeteners as a safe and effective means of reducing and maintaining their weight, as well as of managing blood glucose levels,” they stated.