Study ties gum sweetener xylitol to heart attacks - critical summary review

What xylitol is, and where it hides

Xylitol is a sugar alcohol: a substance that sweetens like sugar without being sugar, used as a low-calorie sugar substitute. It exists naturally in some foods, but only in very small amounts. What ends up in manufactured products is added — often in quantities around a thousand times higher than what nature puts there.

The list of places it turns up is longer than most shoppers would guess. According to the reporting on the new research, xylitol is used to sweeten chewing gum, toothpaste and other oral care products, jam, yoghurt, ice cream, and a range of foods and drinks. Much of that reaches people through items bought precisely because they look like the healthier option: the sugar-free gum, the diet version, the low-calorie dessert.

That perception has had official backing. As the researchers themselves put it, sweeteners of this type "are generally regarded as safe by regulatory agencies", and Professor Dan Atar, an expert member of the European Society of Cardiology's communication committee, noted that "the safety ratings had been good and granted by regulatory authorities".

What has not existed, despite the ingredient's growing use, is much long-term evidence either way: the Guardian reports that the long-term health impacts of xylitol have never been widely studied. That is the gap the new work tries to fill.

What the study found: risk that rises with the dose

At the European Society of Cardiology's annual congress in Munich — the world's largest heart conference — researchers presented what the Guardian describes as the largest study of its kind on xylitol.

The team followed two large groups of people, more than 17,700 participants in total, drawn from the Canadian Longitudinal Study on Aging and from EPIC-Norfolk, a long-running British health study. Instead of asking people what they ate, the researchers measured how much xylitol was circulating in their blood, then compared the quarter of participants with the highest levels against the quarter with the lowest.

In the Canadian group, those with the most xylitol in their blood were 57% more likely to die or to suffer a heart attack or stroke within six years than those with the least. In the British group, followed for up to 30 years, the same comparison showed an 18% higher risk of those events.

Two details matter more than the headline percentages. First, the middle groups fitted the pattern: the more xylitol in the blood, the higher the rate of cardiovascular events — what researchers call a dose-dependent relationship, and one of the signs that an association may not be accidental. Second, the increase held regardless of who the participants were. The researchers reported it was consistent across age and sex, and independent of body mass index, high blood pressure, diabetes and blood fat levels — the very factors that might otherwise explain why someone reaches for low-calorie products in the first place.

The platelet clue

An association only becomes interesting when there is a plausible way for it to work. Here there is one, and it comes from the same team's earlier laboratory research.

"In previous studies, we showed that xylitol can enhance the ability of platelets to form clots," said Dr Marco Witkowski, of the Charité university hospital in Berlin, who presented the findings. Platelets are the blood cells that clump together to stop bleeding; when they clump where they should not, the result can be the blockage behind a heart attack or a stroke. Witkowski and colleagues had also previously found that high blood levels of xylitol were linked to adverse heart events in high-risk patients over a three-year period.

That is why cardiologists are treating this as more than a statistical curiosity. Dr Aseem Malhotra, a London-based cardiologist and public health campaigner who was not involved in the research, told Fox News Digital that "these disturbing findings with plausible mechanism of xylitol increasing cardiovascular risk should be taken very seriously".

What the study cannot say

The research is observational. It watched what happened to people; it did not assign anyone to consume xylitol or avoid it. That means it can show that high blood levels and cardiovascular events travel together, not that one caused the other.

There is a second, less obvious limit. The report does not establish whether a high blood level of xylitol reflects what someone ate: the body also produces this sugar alcohol on its own, as part of glucose metabolism. So the measurement at the centre of the study is not a straightforward readout of diet.

Atar put the caveat this way: "As with all observational studies, causalities are difficult to infer, but this work shows that further studies are mandated into this societally important topic." Witkowski's own framing was about the size of the blind spot rather than the size of the danger: the findings, he said, "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".

What doctors and heart charities are saying

The reaction has been consistent in shape: take it seriously, do not over-read it, and do not respond by going back to sugar.

Dell Stanford, a senior dietitian at the British Heart Foundation, a charity, said risks to heart health build up over time, and that it is vital to make sure what is added to foods does not contribute. "Artificial sweeteners such as xylitol are found in many foods and drinks, and people may assume they are the healthier choice, so consume more than they realise," she said. "This study adds to growing evidence that artificial sweeteners could have an impact on our health."

She also drew the line the study does not cross: it "can only show an association between higher xylitol levels and cardiovascular events, rather than proving that xylitol directly caused them", and "it is not a green light to have more sugar instead, as we still need to reduce our free sugar intake".

Malhotra goes further in his own practice. He said he sees patients whose anxiety and palpitations resolve once they stop taking artificial sweeteners, and that he advises all of them to avoid processed sugars and artificial sweeteners for six weeks. Fox News Digital, the US news outlet, said it had contacted several food and beverage trade groups for comment; no industry response appears in its report.

What to do with this information

The concrete step available today is a small one: know where xylitol actually is. It is not only in obviously sweet products. The reporting on this study names chewing gum, jam, yoghurt, ice cream, drinks, toothpaste and other dental care products — which means the ingredients list, not the front of the pack, is where it shows up. Stanford's point is precisely that people consume more than they realise, because the products carrying it read as the careful choice.

The second step is what the sources are unanimous about: none of them suggests swapping sweetener back for sugar. Stanford's advice is to cut free sugar intake as well, and to reduce processed foods and drinks that tend to be high in sugar, salt or sweeteners, in favour of a balanced diet. That is the recommendation that survives whichever way the causal question is eventually settled.

And that question is open. What is established so far is an association, measured in two large populations, that grows with the amount of xylitol in the blood, holds across age, sex and the usual cardiac risk factors, and comes with a laboratory mechanism involving clot-forming platelets. What is not established is whether xylitol causes those events, whether blood levels reflect how much people eat, and what quantity — if any — would count as too much. Regulators currently treat these sweeteners as safe, and no source in this reporting says that has changed. What the researchers are asking for is the studies that would answer the question, at a moment when, as Witkowski noted, the amount of xylitol going into products keeps rising.