Diet soda may raise odds of vascular events; salt linked to stroke risk


Drinking diet soda could have much higher risk of vascular events compared to those who do not consume soda at all, according to research presented at the American Stroke Association’s International Stroke Conference 2011.


In findings involving 2,564 people in the large, multi-ethnic Northern Manhattan Study (NOMAS), scientists said people who drank diet soda every day had a 61% higher risk of vascular events than those who reported no soda drinking. 


“If our results are confirmed with future studies, then it would suggest that diet soda may not be the optimal substitute for sugar-sweetened beverages for protection against vascular outcomes,” said Hannah Gardener, lead author and epidemiologist at the University of Miami, Miller School of Medicine, Miami, USA.


In a separate research using 2,657 participants also in the NOMAS study, scientists found that high salt intake, independent of the hypertension it causes, was linked to a dramatically increased risk of ischaemic strokes. The results showed that people who consumed more than 4,000mg of sodium per day had more than double the risk of stroke compared to those consuming less than 1,500mg per day.


In the soda study, 559 vascular events occurred, including ischaemic and hemorrhagic stroke, during an average follow-up of 9.3 years. Researchers accounted for participants’ age, sex, race or ethnicity, smoking status, exercise, alcohol consumption and daily caloric intake. And even after researchers also accounted for patients’ metabolic syndrome, peripheral vascular disease and heart disease history, the increased risk persisted at a rate 48% higher.


In the sodium research, 187 ischaemic strokes were reported during 9.7 years of follow-up. Stroke risk, independent of hypertension, increased 16% for every 500mg of sodium consumed a day, the scientists calculated. Those figures included adjustment for age, sex, race/ethnicity, education, alcohol use, exercise, daily caloric intake, smoking status, diabetes, high cholesterol, high blood pressure and previous heart disease.


Only a third of participants met the current US Dietary Guidelines for Americans that recommend daily sodium intake fall below 2,300mg, or about a teaspoon of salt, Gardener said. Only 12% of subjects met the American Heart Association’s recommendations to consume less than 1,500mg a day. Average intake was 3,031 milligrams.


“The take-home message is that high sodium intake is a risk factor for ischaemic stroke among people with hypertension as well as among those without hypertension, underscoring the importance of limiting consumption of high sodium foods for stroke prevention,” Gardener said.

Participants’ reporting their dietary behavior is a key limitation of both studies, Gardener added.


In the soda study, investigators also lacked data on types of diet and regular drinks consumed, preventing analysis of whether variations among brands or changes over time in coloring and sweeteners might have played a role.


NOMAS  is a collaboration of investigators at Columbia University in New York and Miami’s Miller School of Medicine, launched in 1993 to examine stroke incidence and risk factors in a multi-ethnic urban population. A total of 3,298 participants over 40 years old (average age 69) were enrolled through 2001 and continue to be followed. Sixty-three per cent were women, 21% were white, 24% black and 53% Hispanic.


Funding for both studies was provided by a Javits award from The National Institute of Neurological Disorders and Stroke and the Evelyn F. McKnight Brain Institute.