Coke Zero probably isn’t great for your heart, but the picture is more nuanced than a simple yes or no. Several large studies have linked the artificial sweeteners in Coke Zero, specifically aspartame and acesulfame potassium, to modest increases in cardiovascular risk. The effects are not dramatic, and they’re smaller than the well-established damage caused by sugary sodas. But they’re consistent enough that major health organizations now recommend against relying on these drinks as a “healthy” alternative.
What the Largest Studies Found
The most detailed evidence comes from the NutriNet-Santé cohort, a long-running French study that tracked over 100,000 adults and their dietary habits. Published in The BMJ, the results showed that aspartame (the primary sweetener in Coke Zero) was linked to a 17% higher risk of cerebrovascular events like stroke. Acesulfame potassium, the other sweetener in Coke Zero, was associated with a 40% higher risk of coronary heart disease. These associations held up after researchers adjusted for other dietary and lifestyle factors.
The link was specifically stronger when the sweeteners came from beverages rather than solid food. In other words, drinking your artificial sweeteners appears to carry more risk than eating them in, say, a sugar-free yogurt. This matters because Coke Zero is one of the most popular artificially sweetened beverages worldwide.
A separate study published in an American Heart Association journal found that people who drank more than 2 liters per week of artificially sweetened beverages had a 20% higher risk of atrial fibrillation, an irregular heart rhythm that raises the chances of stroke and heart failure. That risk was actually higher than the 10% increase seen with the same volume of regular sugary drinks, a finding the researchers themselves described as unexpected.
How Aspartame May Affect Your Arteries
For years, the concern about artificial sweeteners was mostly statistical: population studies showed associations, but nobody could explain how a zero-calorie sweetener would damage blood vessels. A 2025 study published in Cell Metabolism identified a plausible mechanism. Aspartame consumption triggers an increase in insulin, which in turn causes cells lining your arteries to release an inflammatory signaling molecule. That molecule attracts immune cells to the artery wall, where they promote the buildup of plaques, the hallmark of atherosclerosis.
This is significant because it provides a biological explanation for what population studies have been observing. It suggests the cardiovascular risk isn’t just a coincidence or the result of unhealthy lifestyle habits that happen to overlap with diet soda consumption.
How It Compares to Regular Coke
This is where context matters. Sugar-sweetened beverages are strongly linked to insulin resistance, weight gain, type 2 diabetes, and heart disease. Those connections are backed by decades of evidence and are not in serious dispute. One study tracking middle-aged adults found that regular soda intake was associated with greater increases in insulin resistance and a higher risk of developing prediabetes, while diet soda intake showed no such association.
So if you’re choosing between a regular Coke and a Coke Zero, the zero-sugar version is almost certainly the lesser risk for metabolic health. The problem is that many people treat diet soda as if it were equivalent to water, drinking multiple cans a day without a second thought. The research suggests that level of consumption carries its own set of cardiovascular concerns, just different ones than sugar does.
What the WHO Recommends
In 2023, the World Health Organization released a guideline explicitly recommending against using non-sugar sweeteners to control body weight or reduce the risk of chronic diseases like heart disease. The WHO’s review found potential undesirable effects from long-term use, including increased risk of type 2 diabetes, cardiovascular disease, and mortality in adults.
The WHO classified this as a “conditional” recommendation, meaning the evidence is suggestive but not airtight. The studies are observational, not randomized trials, so it’s possible that people who drink a lot of diet soda share other traits or habits that contribute to their higher risk. But the pattern has appeared across enough large studies, in enough different populations, that the WHO felt it warranted a formal recommendation.
What This Means for Your Coke Zero Habit
An occasional Coke Zero is unlikely to meaningfully affect your cardiovascular risk. The concerning data involves regular, sustained consumption, particularly at levels above roughly 2 liters per week. At that point, the associations with atrial fibrillation, stroke, and coronary heart disease become statistically significant.
If you’re drinking Coke Zero as a stepping stone away from regular soda, that swap is reasonable and likely net positive for your health. If you’re drinking several cans a day as your default beverage, the accumulating evidence suggests dialing back. Water, sparkling water, and unsweetened tea or coffee remain the options with no cardiovascular red flags attached.