As long as diet soda and other sugar-free products have existed, though, some people have cast suspicion toward the non-nutritive sweeteners that make them possible (this category includes artificial sweeteners like sucralose and aspartame, as well as natural options like stevia). Some of these fears are easy enough to dismiss as urban legends, like a popular chain mail in the 2000s falsely claiming that aspartame was originally developed as ant poison. Yet there have been studies in recent years undercutting the assumption that these products are completely harmless.
Just this month, for instance, researchers in Chile found evidence in mice that sucralose and stevia can potentially alter the gut microbiome and affect genes linked to metabolism and inflammation in negative ways—changes that could even be passed on to later generations. Another study last September found that higher levels of low- or no-calorie sweetener consumption in older adults were associated with a greater rate of cognitive decline, while a May 2025 study found a link between aspartame and worsening atherosclerosis (the build-up of plaque within the arteries), a major risk factor of cardiovascular disease.
While these studies all have their limitations (mice, I’m fond of saying, are not people), it’s reasonable to wonder if these sweeteners could come with a hidden cost to our health. So for this week’s Giz Asks, we reached out to researchers and nutrition experts to get their thoughts on the current science surrounding these products and whether it might be wise to at least cut back on them. Their responses have been edited for clarity and grammar.
Yihai Cao
A cancer researcher and molecular biologist at the Karolinska Institute in Sweden. Cao also co-authored the May 2025 paper on aspartame.
I think from a scientific point of view, we do have evidence that artificial sweeteners may not be as healthy as we thought.
And regarding our discovery last year, we saw that aspartame can elevate insulin levels. Even though we only did this research in animals, not people, I would predict that the same response may exist in humans as well. And this elevation of insulin levels could have actual physiological consequences; it may even trigger the onset of development of certain diseases, like cardiovascular disease, for example, through inflammation.
With this latest paper looking at the gut microbiota, the results don’t surprise me. Anything we eat, or if we’re dosed with something, it can affect the microorganisms in the gut, it can cause changes in the tissue. This isn’t only with artificial sweeteners, but any other food. If you prefer to eat one type of food, then the composition can be changed, since certain bacteria might prefer some types of nutrients and other bacteria prefer the other nutrients. At the end of the day, the ratio between all these microorganisms will be changed. Now, could those changes carry to the next generation? I don’t know. But it could be yes, depending on the next generation. What do they eat? What kind of lifestyle do they have?
Our microbiome can change all the time. And there are good bacteria and bad ones, but there’s no particular type of what makes it healthy. I guess there can be a threshold, though. And if the changes we’re seeing fluctuate within that threshold, that’s okay. But then if they go beyond or below that threshold, then you might get in trouble.
I don’t want to speak with too much authority because I didn’t conduct that experiment. But in general, I believe that our lifestyles matter. Whether we’re exercising or the kinds of physical exercise we’re doing. And also, the foods we eat. I think that matters.
Jotham Suez
A molecular microbiologist at John Hopkins University who focuses on the microbiome. Suez has conducted several animal and human studies on non-nutritive sweeteners.
The cautious answer will be yes—if one can reduce their consumption of artificial sweeteners (and non-nutritive sweeteners more broadly, including natural ones) without replacing them with foods and beverages sweetened with caloric sugars. Excess sugar in the diet is clearly linked to an increased risk of obesity, diabetes, and heart disease, which is why people consume artificial sweeteners instead in the first place. However, there is insufficient evidence that artificial sweeteners promote sustainable weight loss or improve blood glucose control, and they might even contribute to the same conditions they aim to prevent.
There is considerable research on the health impacts of artificial sweeteners in animal models, and most (though not all) studies demonstrate adverse effects. However, it is important to note that evidence in humans for harm from artificial sweeteners is primarily associative—the more artificial sweeteners a person consumes, the greater their risk of diabetes, heart disease, and other related conditions. Whether sweeteners are the cause of the elevated risk is less conclusive. While some human studies show that sweeteners can cause weight gain and disruption of blood glucose control, others find them to be more neutral.
An emerging field of research suggests that this variability between studies can be attributed to how artificial sweeteners interact with the gut microbiome. Individuals who experience worsening of blood glucose control after being exposed to artificial sweeteners have a different makeup of gut bacteria, which is more amenable to disruption by artificial sweeteners—and that disruption has been linked to disrupted glycemic control, a risk factor for diabetes. Therefore, it is possible that there is heterogeneity in the population in how susceptible people are to adverse metabolic impacts of artificial sweeteners.
More causal evidence is needed to fully understand the impact of artificial sweeteners on health, and we still do not know how to predict who will respond poorly to them. However, given that they are not essential for our diet, and the possible risks, it may be prudent to limit their intake.
Christopher Gardner
A dietary researcher at the Stanford Prevention Research Center and lead author of a 2012 scientific advisory statement from the American Heart Association and American Diabetes Association on artificial sweeteners.
Let me just start off by saying that I’m not a fan of sugar substitutes or sugar. I think the whole thing is out of whack in the first place. We eat way too much sugar and the way to get off sugar is not to be on a sugar substitute—it’s to eat real food. But that aside, if you were having a hard time cutting back on sugar, could a sugar substitute help you? Well, there’s very mixed data on that. I actually wrote a report on sugar substitutes for the American Heart Association and we said at the time 14 years ago that the data really sucks. There are not enough studies, and not enough good studies. So it’s very hard to make a conclusion.
As for this new [April 2026] mouse study, here’s my main concern with it. There were three arms in the study: water versus sucralose versus stevia. And I find that problematic. What is the purpose of sucralose and stevia? It’s to replace sugar. So shouldn’t the comparison be sugar, or if you do want to have a water arm in there, shouldn’t there be two comparisons? One water and one sugar.
I do get why they might have used water. Water will not hurt you. So comparing sucralose and stevia to water might be testing whether they are in and of themselves bad for you. But isn’t the more realistic question for the public whether these things are worse for you than sugar, since that’s what you would be displacing if you used it? I find that massively problematic and it’s not the first time. During the 2012 review, I was stunned by how many papers were comparing sugar substitutes with water. And I personally found that the wrong question to be asking.
On the other hand, think about what you can do in a mouse that you can’t do in a human. They looked at two generations. They said here’s the parents, and let’s see if this would carry over to their kids and to their kids’ kids. That’s something you can’t possibly do that with humans.
So what would it take to study this in people? Well, first of all, it’s unethical if you think it might hurt them. I can’t just say, here, have a crap ton of sugar substitutes because I want to see if it hurts you. You can’t recruit people for that. You could recruit people and say, I’m going to have you swap out your sugar for sucralose or stevia or water. I’m going to try to see which one of those works better. So you can do that if you’re displacing the sugar, because most people know that the health professionals think sugar is a bad thing. And you’re helping them avoid a bad thing. And I’m honestly surprised how few studies like that are done.
But there’s also the beverage issue and the food issue. If you’re going to have a coke or a diet coke, that’s pretty straightforward, or a cup of black coffee that you might add in sucralose or stevia. That’s a pretty doable study. But let’s say you’re going to switch to cookies and chips and protein bars and candies. These sugar substitutes can’t replace some of the things that we use sugar in cooking for, like the browning reaction or the smell. So if you’re trying to take advantage of the physical, chemical properties of sugar, you have to add something else to sucralose and stevia, and that makes things harder to study. Because now you’re trying to figure out whether the effects we’re seeing are because of the substitutes or the other things that you added with it.
You would have to run all kinds of studies. With different people for different durations in different doses with different outcomes. And that’s why they do mice. You can do the equivalent of an eight-week study in a week with mice. I tend to do studies in humans, and humans are a pain in the ass. They don’t always eat everything that you give them and they underestimate, overestimate, forget, and lie about what they’re eating and the mice never do that. You have total control over the mice. So while I’m not all that impressed with this study design. I think it may contribute someday.
And personally, I don’t consume things with sucralose or stevia. And I eat too much sugar, but I do try to avoid it as much as I can.
Andrew Kau
An associate professor of medicine (allergy and immunology) at the Washington University School of Medicine in St. Louis.
Artificial sweeteners are incredibly common food additives and are found in a wide variety of everyday foods, beverages and supplements. In principle, they sound like a great idea—these are additives that taste like sugar but have little or no calories. Back in grad school when I was guzzling tons of soda, I reached for the ‘diet’ soda options because I figured that the versions with artificial sweeteners would have less of an impact on my weight.
However, clinical studies showing that artificial sweeteners help with long term weight loss are mixed, at best. And they may even contribute to the development of diabetes and heart disease, though more studies are needed. The long-term consequences of artificial sweetener consumption may be the result of alterations to the gut microbiota, or the collection of bacteria, viruses, fungi, and protists that live in our gut. The microbiota has many roles in gut health, including shaping our metabolism. We also know that the gut microbiota is shaped by our diets: long-term exposure to artificial sweeteners alters the microbiota’s ability to produce beneficial molecules, with the latest study suggesting that the effects of artificial sweeteners can be transferred parent to offspring. Though many of these studies rely on animal models, these findings make me very skeptical of any health benefits of artificial sweeteners. However, I think we should be more concerned about the role of food additives more broadly, and not just artificial sweeteners. Highly processed foods contain a wide range of chemical additives that make them tastier, longer-lasting, and more attractive. Many of these additives also impact the gut microbiota, although the impact of prolonged consumption of these foods requires further work.
At the end of the day, I don’t think a blanket ban on artificial sweeteners is in order, though. Artificial sweeteners, like other chemical additives, have a place in our diets—I just don’t think it should be a big place (I love my sugar-free gum!) Instead, we need to focus more on eating unprocessed, nutritious foods like fruits, vegetables, and lean protein and re-evaluate what is an appropriate amount of food additives we should be consuming. Ultimately, we need to make thoughtful food choices that are guided by high-quality, long-term studies of the health effects of dietary additives.
Laura Bosman
In-house nutrition expert at the European Food Information Council, a non-profit organization billed as providing “accessible, appealing and actionable science-based information on food and health.”
Do we need to get rid of artificial sweeteners? Short answer: no, but studies like this are a useful reminder that the science around non-nutritive sweeteners is still evolving and that how we interpret new findings matters.
Recently, a new mouse study was published that suggested non-nutritive sweeteners, particularly sucralose and stevia, may harm the gut microbiome and affect genes linked to metabolism and inflammation. That raises important scientific questions. But it’s important to understand what this type of research can, and can’t, tell us. This animal study looked at biological markers, not real-world health outcomes in people, such as type 2 diabetes, cardiovascular disease, or weight gain. Results from animal research don’t always translate to humans.
Animal studies are often an early step in the evidence process. They’re valuable for understanding potential mechanisms, but they don’t directly predict what happens in people. Human diets are more complex, exposure patterns vary widely, and the gut microbiome itself is highly individual. A helpful way to think about it is like a jigsaw puzzle: studies like this add pieces, but they don’t complete the full picture. Findings like these help generate hypotheses, but to change public health advice, we would need consistent findings from well-designed human studies showing clear, meaningful effects at typical consumption levels. This study on its own doesn’t justify changing dietary guidance or consumer behavior.
When we look at that broader human evidence, regulatory authorities such as the European Food Safety Authority (EFSA) have repeatedly concluded that approved sweeteners are safe within established acceptable daily intake (ADI) levels. These limits are set with large safety margins. Within these safe limits, the evidence base suggests that sweeteners do not cause sugar-taste habituation nor diseases like cancer or diabetes in humans.
At the same time, the World Health Organization (WHO) has issued guidance suggesting that non-sugar sweeteners should not be relied upon for weight control or reducing the risk of non-communicable diseases (in people without type 2 diabetes). This recommendation is not about safety, but about effectiveness for long-term weight management, and it remains a topic of scientific debate. Evidence from short-term randomized controlled trials shows that higher consumption of non-sugar sweeteners is linked with lower body weight and body mass index. In contrast, longer-term observational studies have associated higher intakes with increased body weight and higher risks of type 2 diabetes and cardiovascular disease. However, these types of studies cannot establish cause and effect and are more difficult to interpret.
Because sweeteners are food additives, there are no recommended intake targets in the same way as for nutrients like carbohydrates, proteins, or fats. Their potential benefits also depend strongly on context, for example, an individual’s body weight, whether sweeteners replace sugar in foods or drinks, how long the substitution is maintained, and the type of sweetener used.
Based on the current evidence, expert panels advising public health authorities generally agree that sweeteners can support weight loss and weight management in some situations and may be useful for people with diabetes to help manage blood glucose. However, there is insufficient evidence to support a widespread, long-term replacement of sugars across all sweet products, and non-sugar sweetened drinks should not be seen as a substitute for water. Gradually adjusting your taste preferences to less sweet tastes may be a useful strategy to support reducing sugar intake in the diet, with low-calorie sweeteners acting as one possible supportive tool in that transition.
Ultimately, the strongest evidence still points to overall diet quality as the key driver of health. Sweeteners can have a place within that, but in moderation and in context.
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