Diet soda may benefit the waistline, but a new study suggests that people who drink it every day have a heightened risk of heart attack and stroke.
The study, which followed almost 2,600 older adults for a decade, found that those who drank diet soda every day were 44% more likely than non-drinkers to suffer a heart attack or stroke.
Of course, the findings, reported online in the Journal of General Internal Medicine, don't prove that the sugar-free drinks are actually to blame.
There may be other things about diet-soda lovers that explain the connection, researchers say.
Diet soda drinkers tend to be heavier
"What we saw was an association," said lead researcher Dr Hannah Gardener, of the University Of Miami Miller School Of Medicine. "These people may tend to have more unhealthy habits."
She and her colleagues tried to account for that, Gardener told Reuters Health.
Daily diet-soda drinkers did tend to be heavier and more often have heart risk factors such as high blood pressure, diabetes and unhealthy cholesterol levels.
That all suggests that people who were trying to shed pounds or manage existing health problems often opted for a diet soda over the sugar-laden variety.
Soda drinkers have cardiovascular risk factors
But even after the researchers factored in those differences – along with people's reported diet and exercise habits – they found that daily diet soda was linked to a 44% higher chance of heart attack or stroke.
Nevertheless, Dr Gardener said, it's impossible for a study to capture all the variables that could be at work.
The findings do build on a few recent studies that also found diet-soda drinkers are more likely to have certain cardiovascular risk factors, like high blood pressure or high blood sugar.
This is the first study, Dr Gardener said, to look at actual vascular events.
Not clear if diet soda contributes to health risk
The findings are based on 2,564 New York City adults who were 69 years old, on average, at the outset. Over the next decade, 591 men and women had a heart attack, stroke or died of cardiovascular causes.
That included 31% of the 163 people who were daily diet-soda drinkers at the study's start. In contrast, 22% of people who rarely or never drank diet soda went on to have a heart attack or stroke.
There was no increased risk linked to less-than-daily consumption. Nor was regular soda tied to heart attacks and strokes.
If diet soda itself somehow contributes to health risks, it's not clear how, Dr Gardener said.
Swop regular soda with diet version
There's research in rats suggesting that artificial sweeteners can end up boosting food intake and weight. But whether results in rodents translate to humans is unknown.
"I don't think people should change their behaviour based on this study," Dr Gardener said. "And I wouldn't advocate drinking regular soda instead."
Regular soda is high in kilojoules, and for people who need to shed kg, experts often suggest swapping regular soda for the diet version.
A study found that the advice may be sound. Obese people who were randomly assigned to drink water or diet drinks in place of sugary ones lost about five kg over six months.
Dr Gardener said that further studies such as hers are still needed to confirm a connection between diet soda and cardiovascular trouble.
(Amy Norton, Reuters Health, February 2012)