What is “worse” for you, Coke or Diet Coke?. Photo / Getty Images
From aspartame to sucralose, here’s how five popular sweeteners could be impacting your health.
What is “worse” for you, Coke or Diet Coke? Of all the areas of health confusion, few are as baffling as the question of whether to consume the “fat” version of a product, or sugar-free one, without any calories.
While it has long been established that consuming too much sugar can lead to obesity, Type 2 diabetes and heart problems, there is a growing body of evidence that sweeteners aren’t necessarily the healthy alternative we’re led to believe.
Last week, a new study found that people who consumed the largest amount of sweeteners (more than 190mg per day) such as aspartame and saccharin saw a 62% faster decline in their cognitive function than those who consumed 20mg per day. A can of diet fizzy drink contains around 200mg. This is just one of many studies linking sweeteners to a range of health problems, from cardiovascular disease and inflammation to disrupted gut health and even cancer.
Let’s take a closer look at what we know so far about the five most common sweeteners and their potential health effects.
Perhaps the most widely used sweetener, found in products ranging from Diet Coke to breakfast cereals, ice cream, low-sugar yoghurts, and sugar-free chewing gum. At 180 to 200 times sweeter than sugar, aspartame’s main disadvantage is that it falls apart and loses sweetness when heated, limiting its usability in desserts.
However, ever since aspartame was first approved by regulators in the 1970s, it has been dogged by suggestions it might be linked to health concerns. In the mid-2000s, studies of lab rats suggested that high doses of the sweetener consumed over a long period of time may be associated with lymphoma and leukaemia. While the result was ultimately dismissed, the findings of various epidemiological investigations have continued to raise concerns.
In 2022, an analysis of more than a decade’s worth of dietary records from 102,865 adults in France linked higher consumption of aspartame and another sweetener called acesulfame-K, to various cancers. Subsequent investigations last year also linked high consumption of foods flavoured with aspartame and other artificial sweeteners to cardiovascular disease and Type 2 diabetes.
A small minority of people may even develop acute neurological symptoms from consuming aspartame. Erik Millstone, a professor of science policy at the University of Sussex, has spent decades researching aspartame, and says this is thought to be an adverse reaction to phenylalanine, an amino acid produced when aspartame is metabolised. “From the evidence I’ve seen, I think it’s probably no fewer than 3% of consumers, but no more than 10%,” he says. “The problems that emerge are things like headaches, blurred vision, and in a small proportion of cases, quite severe epileptic like seizures. These people probably have difficulty coping with what is in effect quite a large pulse of phenylalanine into their body.”
Sucralose is also often used in combination with acesulfame potassium in foods ranging from condiments to sugar-free jams, fruit spreads, salad dressing, diet sodas and chewing gum.
But while one of the purported aims of sweeteners has been to try to reduce the problem of excessive sugar consumption leading to weight gain, it seems that they themselves may actually alter our metabolism, particularly when combined with our food ingredients.
A study released in late March from the University of Southern California’s (USC) Keck School of Medicine revealed that the appetites of people who drank water containing the artificial sweetener, sucralose, increased by nearly 20%, compared with those who drank water with “regular” table sugar.
Professor Dana Small, a neuroscientist at McGill University in Canada and one of the world’s leading experts in sucralose, also conducted a pioneering experiment in 2020 which found that drinks in which sucralose is combined with carbohydrates, altered brain and metabolic responses to that carbohydrate, making them more vulnerable to weight gain.
“Our paper showed that sucralose combined with the carbohydrate maltodextrin changes quite rapidly the brain’s physiological response to sugars,” says Small.
Meanwhile in 2023, a study raised concerns about the sweetener with researchers from universities in North Carolina conducting experiments with human gut cells which suggested that sucralose-6-acetate, a chemical within sucralose, can damage DNA, something which could increase levels of harmful oxidative stress and inflammatory molecules in the gut.
Neotame, or E961, has been subtly introduced in various products ranging from canned fruit, jelly, with some carbonated drinks, dairy products, and industrially manufactured cakes. The European Food Safety Authority (EFSA) announced it was safe to use in foods and soft drinks in 2007, an alternative to aspartame that was more than 8000 times sweeter than sugar. It has gained popularity with manufacturers as it lacks the problematic aftertastes which can be an issue with some sweeteners, while remaining stable even when exposed to production temperatures of up to 450C.
“Neotame was developed with the aim of being a more stable and sweet version of the traditional sweetener,” says Dr Havovi Chichger, a researcher at Anglia Ruskin University who has been studying neotame. “We became interested in neotame because it is very unusual – it is chemically similar to traditional sweeteners but it is so intensely sweet in comparison, over 100 times sweeter than sweeteners such as sucralose.”
However, Chichger published a study in the journal Frontiers of Nutrition which suggested that it may be capable of damaging cells in the lining of the intestine. These cells play important roles in digesting food, absorbing nutrients, and shielding the body from microbial infections.
While the average human would still be unlikely to consume this much neotame in a day through food and drinks, it seems that relatively low concentrations of the sweetener can still disrupt the microbiome in a variety of ways which could make consumers more prone to bowel disease and even blood poisoning.
“At concentrations which a person could very easily consume on a daily basis, our studies show a breakdown of the gut barrier and a shift in bacteria to a more damaging behaviour, including increased invasion of healthy gut cells leading to cell death,” says Chichger.
First approved in the late 1980s, acesulfame potassium has been used in combination with aspartame in Diet Coke since the mid-2000s, while it is also found in salad dressings and sauces, jam, jelly, and marmalade, ice cream and other dairy products and even toothpaste and mouthwash.
Like aspartame and other sweeteners, it has been speculated that acesulfame potassium’s intense flavour could disrupt the body’s naturally hormonal processes which govern blood sugar control, causing excessive amounts of the hormone insulin to be released, one of the causative factors in the progression towards Type 2 diabetes. One study suggested that it might even increase the amount of sugar absorbed by cells in the gut, a possible mechanism for driving gut inflammation.
However, acesulfame potassium tends to be combined with other sweeteners to mask its bitter aftertaste, and according to Dr Jotham Suez, an assistant professor at Johns Hopkins Bloomberg School of Public Health, right now it is difficult to pin some of these health concerns on individual sweetener because many foods and drinks contain a blend of them.
“At the moment you cannot say that one sweetener is more associated with harm than others,” he says. “But there is evidence, which is not negligible, showing a potential causal link between consumption of foods and beverages that contain these sweeteners, and increased weight gain and disrupted glucose homeostasis, so potentially elevated blood glucose.”
This is the original sweetener, having been discovered way back in 1879. Like aspartame, saccharin has faced controversy over the years regarding accusations that it may be carcinogenic, following a Canadian study in the 1970s which linked the sweetener to bladder cancer in rats.
However, no clear evidence has ever connected saccharin consumption with bladder cancer in humans, and saccharin is currently found in many processed foods branded as being low-calorie, such as fruit juices, sweets, jams, jellies, and cookies.
But like other sweeteners, concerns still abound that saccharin may disrupt the gut in various ways with potentially wider consequences for our health.
At the same time, Suez predicts that there are some people who are more vulnerable to the negative effects of sweeteners than others. With personalised nutrition technologies such as microbiome sequencing becoming more popular with consumers around the world, he feels that the future could involve looking for signals within the gut microbiome which can indicate how sweeteners might affect that person.
“As we try to think about the next step, it’s potentially to try and really develop some algorithms to be able to predict who might benefit from sweeteners because that person is not negatively impacted by their consumption, versus those that are,” he says.
What are the safest sweeteners?
Technically, all approved sweeteners are considered safe, and come with an acceptable daily intake (ADI) set by governments. Some people prefer to use stevia, a natural sweetener made from the leaves of the Stevia rebaudiana plant, as it’s less processed, but there currently isn’t a lot of evidence to say one sweetener is “safer” than another.
Are artificial sweeteners linked to blood clots?
One 2024 study linked a 30g serving of the sweetener erythritol to an increased risk of blood clots. However, the study was small (it involved 20 volunteers), though researchers did suggest limiting your intake of this sweetener if you’re at an increased risk of thrombosis. Erythritol is found in a range of products including sweets, baked goods and protein bars.