The billboard looming over the San Diego (405) Freeway declares that Diet Coke should be “the first drink of the rest of your day.”

Maybe not.

If diet soda is your favorite daily quaff, you may want to consider cutting back. A study published in the January issue of the Journal of General Internal Medicine describes a possible link between daily consumption of diet soda and heightened risk of heart attack, stroke, and vascular death. These findings created a stir when presented as preliminary results last year, and now the researchers have provided the full analysis of the possible relationship.

This isn’t the first time diet soda has come under suspicion for being less than healthy—previous studies have looked at the link between diet soda and obesity, diabetes, and metabolic syndrome. But this is the first research that suggests an association between daily diet soda consumption and vascular events.

Researchers looked at data involving a multiethnic population of more than 2,500 participants in a National Institutes of Health-funded study on stroke incidence, risk, and prognosis. They used a food questionnaire to track patterns of diet and regular soft drink consumption.

Scientists from the University of Miami Miller School of Medicine and Columbia University Medical Center found that among those who drank diet soda daily, there was a significantly higher incidence of vascular events over a 10-year period. Daily diet soda drinkers had 43 percent more vascular events than those who drank regular soda, or who drank between one diet soda a month and six per week. In contrast, those who drank regular soda or who were categorized as light diet soda drinkers did not have increased risk of these health consequences.

In the analysis, the researchers controlled for age, gender, ethnicity, and education as well as eating patterns, body mass index, physical activity, and alcohol consumption. The study also took into account high blood pressure, diabetes, and metabolic syndrome, which includes other risk factors such as large waistline, high triglycerides, and high cholesterol. This rules out the possibility that the people who drank diet soda daily were already at higher risk due to other reasons.

With obesity a growing problem in the U.S., diet soda is often identified as a healthier alternative for people who need to control their intake of sugar and calories. In what could be perceived as irony or a pre-emptive strike, this week Diet Coke will donate to “The Heart Truth” campaign sponsored by the National Heart, Lung, and Blood Institute as part of its observance of Heart Month.
Hannah Gardener, Sc.D., epidemiologist at the University of Miami Miller School of Medicine and lead author of the study notes that more research is warranted before concluding that diet soft drink consumption has potential health consequences.

While it’s too soon to draw a straight line between diet soda and the serious health events described in Gardener’s study, easing up on daily diet soda can’t hurt in the meantime.

“It is a good idea to encourage water over all beverages and diet drinks of any kind in moderation,” says Michelle Fino, public health nutritionist for the City of Long Beach.

If you’d crave the sparkle and fizz of diet soda, try drinking sparkling water with a fillip of juice for color and flavor.