Just a few cans of diet soda a day could increase your risk of suffering a potentially fatal heart attack or stroke, a Swedish study suggests.
Scientists found aspartame, a commonly-used artificial sweetener added to Diet Coke, candy and ketchup, contributed to a worrying build up of fat in the arteries.
This collection of fat deposits, called atherosclerosis, leads to the arteries narrowing, restricting the flow of blood to and from the heart — damaging the organ over time.
Parts of the fatty plaque can break off triggering dangerous blockages in blood vessels, risking heart attack and stroke.
While the study was conducted on mice, the authors said their findings had worrying implications considering how widespread artificial sweeteners are.
However, independent experts have warned that while the findings are worrying, the study may not be wholly reliable.
In the experiment, scientists from the Karolinska Institute, alongside colleagues in China and the US, fed groups of rodents a daily diet containing small amounts of aspartame for 12 weeks.
They described this as being equivalent to human having three cans of diet soda containing the sweetener per day.
Just a few cans of diet soda a day could increase your risk of suffering a potentially fatal heart attack or stroke, a Swedish study suggests
Experts then compared the mice’s tissues to a control group not fed aspartame.
They found aspartame-fed mice had developed more fatty plaques in their arteries and had higher levels of inflammation — both signs of cardiovascular disease.
Further tests of the mice’s blood suggested aspartame was leading to a blood sugar spike similar to that seen with real sugar.
Writing in the journal Cell Metabolism, the authors said this spike led to increased production of a protein called CX3CL1.
Senior author Professor Yihai Cao, an expert in chronic disease, said this protein acted like a glue to the inner lining of the blood vessels, helping plaque to build-up.
‘Because blood flow through the artery is strong and robust, most chemicals would be quickly washed away as the heart pumps,’ he said.
‘Surprisingly, not CX3CL1. It stays glued to the surface of the inner lining of blood vessels. There, it acts like a bait, catching cells as they pass by’.
While acknowledging the study has limited implications for people, Professor Cao said the team now plans to verify the findings in humans.
The above graphic shows some of the favorite snacks in the US that contain the sugar sweetener aspartame. Smint is a breath freshener sold in parts of the US
‘Artificial sweeteners have penetrated almost all kinds of food, so we have to know the long-term health impact,’ he said.
Some independent experts have welcomed the findings, even claiming it should prompt us to reduce our intake of artificial sweeteners.
Professor Mark Wahlqvist, an expert in medicine at Monash University in Melbourne Australia and past president of the International Union of Nutritional Sciences, called the results ‘disturbing’.
‘We should stop the inappropriate use of sugar substitutes,’ he said.
Dr Yutang Wang, an expert in biomedical sciences at Federation University Australia, added: ‘It may be time to reconsider our consumption of artificially sweetened products.’
‘Reducing their intake could be a simple yet powerful step to protect ourselves from heart attacks and strokes.’
Other experts however have urged caution.
Professor Oliver Jones, an expert in chemistry at RMIT University in Melbourne, said the structure of the experiment on mice needed to be considered.
‘The authors used a particular type of lab mouse called an ApoE mouse, which is bred to be prone to heart disease,’ he said.
‘They also fed it a high-fat, high-cholesterol diet, which itself increases the risk of heart disease.
‘They also don’t seem to have measured how much of the aspartame water the mice drank, or the aspartame level in the blood, so it is unknown what the mice actually received.’
He also said opting for full sugar sodas and sweets is not necassarily better for your health than choosing products with artificial sweeteners.
‘Even if aspartame did cause some increase in cardiovascular risk… then that risk would likely be very small compared to things like high fat/high sugar diets and lack of exercise,’ he said.
British experts have largely echoed these concerns.
Professor Naveed Sattar, an expert in cardiometabolic medicine at the University of Glasgow, said further research in humans is now needed.
‘This seems like worrying findings but of course, before it can taken seriously, the findings have to be replicated in man,’ he said.
‘For now, I remain happy to take sweeteners and related diet beverages instead of sugar filled drinks as the former limits excess calorie intake.’
Professor James Leiper, director of research at the British Heart Foundation, added: ‘These sweeteners are now found in many foods and drinks, and people are probably consuming more than they realise.’
‘But this research is not a green light to have more sugar instead. We all need to reduce our intake of the processed foods and beverages that contain high levels of fat, sugars, sweeteners and salt.
‘This is the best way of ensuring a healthy diet and a lowered risk of heart and circulatory disease.’
Concerns about the impact artificial sweeteners, which are also added to yoghurt and some cereals, could be having on heart health have circulated for years.
In 2022 French experts found people who consume just 78mg/day, similar to what is found in half a can of diet soda, were up to a tenth more likely to suffer a heart attack and fifth more likely to suffer a stroke.
Another last year suggested people who drank about seven cans of artificially sweetened beverages like diet soda per week had a 20 percent higher risk of developing an irregular heartbeat.
They found that those who drank roughly seven cans of artificially sweetened beverages per week had a 20 percent higher risk of developing atrial fibrillation than those who didn’t drink them.
However, critics claim such studies are only observational, unable to prove artificial sweeteners are the culprit and cannot rule out external factors, like exercise levels, could be to blame.
Concerns have also been raised about links between artificial sweeteners and cancer.
These fears were heightened in 2023 after the World Health Organisation controversially classified the artificial sweetener aspartame, found in drinks like Diet Coke, as ‘possibly carcinogenic to humans’.
However, the UN agency ruled it only posed a risk to those who consumed massive amounts and that an 11 stone (70kg) adult could safely drink about 14 cans a day.
And like the most recent study, experts are keen to point out that the potential risks of artificial sweeteners are being overblown compared to the sugar they have replaced.
