At the European Society of Cardiology congress in Munich held in late August, there was chatter among the attendees about one particular presentation.
The presentation was by Dr Marco Witkowski from the Charité University Hospital in Berlin, whose previous work had suggested that sugar substitutes, such as the sugar alcohol xylitol, may increase the body’s tendency to form blood clots. In a small study, he had also found high levels of xylitol in the blood was associated with higher risk of cardiovascular events.
Now, Witkowski shared the findings based on a much larger group – 17,710 adults over a period of up to 30 years.
After six years, the risk of a heart attack or stroke was 57 per cent greater among those with the highest xylitol levels in their blood. After 30 years, it was 18 per cent more likely. This was after controlling for age, sex, smoking status, lipid levels, diabetes and hypertension.
The results, Witkowski said, indicated that the higher the xylitol blood levels, the higher the cardiovascular event rate.
“Artificial sweeteners are consumed by people who think they are healthier than sugar, and they are generally regarded as safe by regulatory agencies,” he said in a statement.
“Our long-term findings in the general population highlight how little we know about the cardiovascular safety of xylitol and indicate that further studies are warranted, especially as the amount of xylitol in products continues to increase.”
‘There has always been suspicion about artificial sweeteners’
Alongside the rise of diet culture in the 1960s, increasing knowledge about the deleterious effects of high sugar consumption on metabolic health and, later, the anti-sugar movement, sugar substitutes became ubiquitous.
They are in everything from toothpaste, medicine and chewing gum to jams and spreads, yoghurt, drinks, pastries and sugar-free cakes.
They have often been recommended to those with diabetes, obesity or heart health issues as a way to avoid the weight gain, liver and metabolic issues caused from excess sugar.
But, some experts have wondered if we have substituted one problem for another.
Animal studies, for instance, have suggested that artificial sweeteners may negatively affect the gut microbiome, inflammation and metabolic regulation.
“There’s always been a little bit of suspicion over artificial sweeteners,” says Professor Garry Jennings, the Heart Foundation’s chief medical adviser. “But nobody’s ever been able to nail it down clearly one way or the other.”
Does this new research finally nail it down?
No, says Professor Tom Marwick of The Baker Heart and Diabetes Institute.
Beyond the reality that the research is observational and cannot prove causation, there are several issues.
Firstly, we don’t eat sweeteners like xylitol on their own. We consume them in packaged foods and fizzy drinks. Is it the xylitol causing the issue or the ultra-processed food it’s a part of?
Secondly, people consuming artificial sweeteners are likely to be doing so because they have another illness, such as obesity or diabetes.
“They may well have other issues that lead to high cardiovascular risk, of which the xylitol in the blood is just a marker,” says Jennings.
The third factor is that we can consume xylitol in foods and beverages, but our bodies also produce it as a byproduct of glucose metabolism.
So, we can’t be sure that high levels of xylitol in the blood are because of xylitol intake.
“The half-life of xylitol is about 13 minutes, meaning that maintaining high levels requires significant and recurrent intake,” explains Marwick. “It’s more plausible that the high xylitol levels arose as a byproduct of glucose metabolism. It’s likely that insulin resistance is driving the xylitol levels and events.”
Insulin resistance has been rising in Australia, a trend largely driven by the growing consumption of processed foods.
Sugar substitutes ‘are not the solution’
“Swapping out sugar and swapping in sweeteners is not the solution,” says dietitian and Foodwatch chief executive, Jemma O’Hanlon.
“Wherever possible we should be reducing foods containing sweeteners.”
In 2023, The World Health Organisation released a new guideline recommending against the use of non-sugar sweeteners for weight management and chronic disease reduction.
“It also suggests there may be undesirable effects from long-term use, including an increased risk of type 2 diabetes, cardiovascular disease and early death,” says O’Hanlon, noting that xylitol wasn’t included under the scope of their review.
Cardiovascular events do appear to be more common among people with high levels of xylitol in their blood, but why they have high levels is still unclear.
If your diet is well-balanced, consists mostly of whole foods and not too much of anything, then it is probably irrelevant whether your favourite treat contains sugar, xylitol or another sweetener.
Says Jennings, “This study is something to take note of, to try and confirm with more direct studies which can look at cause and effect.”
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Sarah Berry is a lifestyle and health writer at The Sydney Morning Herald and The Age.Connect via X or email.
