Are artificial sweeteners safe? It's a bit complicated.

For years, artificial sweeteners were promoted as a healthier alternative to table sugar. But several studies over the past few years have suggested that the sweeteners may not necessarily be good for your health.

On Thursday, after assessing the popular artificial sweetener aspartame, the World Health Organization (WHO) found that it's "possibly carcinogenic to humans," meaning it could cause cancer, while also reaffirming that the current acceptable daily intake of aspartame — 40 mg per kilograms of body weight per day (roughly 12 cans of Diet Coke for a 130-pound person) — is still safe to consume. The FDA reportedly disagrees with WHO's assessment of the sweetener, however, saying in a statement that "'possibly carcinogenic to humans' does not mean that aspartame is actually linked to cancer."

Aspartame isn't the only controversial artificial sweetener. In a May 2023 study published in the Journal of Toxicology and Environmental Health, Part B, researchers conducted lab-based experiments on the impact of sucralose (an artificial sweetener marketed as Splenda) and sucralose-6-acetate (a form of sucralose that occurs after your body breaks down the sweetener) on human tissue and made several concerning findings.

The researchers discovered that sucralose-6-acetate is genotoxic, which means that it can damage DNA. The chemical also caused intestinal cells to activate genes linked with inflammation and cancer.

The researchers noted that sucralose can damage the cells that line the wall of the gut, leading to leaky gut. Leaky gut syndrome, in case you're not familiar with it, is a theory that when your gut "leaks," it releases elements that would normally be removed in feces into the bloodstream, where they can cause inflammation.

"Overall, the toxicological and pharmacokinetic findings for sucralose-6-acetate raise significant health concerns regarding the safety and regulatory status of sucralose itself," the researchers wrote.

The study comes shortly after the WHO warned that using artificial sweeteners for weight control could potentially contribute to health issues.

Given how popular sucralose and other artificial sweeteners are, it's understandable to have questions about their safety. Here's what you need to know.

What does other research say about artificial sweeteners?

There have been a few recent studies on artificial sweeteners (also known as non-sugar sweeteners) that suggest some people should be cautious about using them. While the WHO's recent assessment calls for more research into aspartame, their recommendation from May was based on findings of a systematic review that found artificial sweeteners don't have any long-term benefit in reducing body fat in adults or children. But the WHO also noted the review suggested that long-term use of artificial sweeteners could cause an increased risk of type 2 diabetes, cardiovascular disease and even death in adults.

A 2022 study of more than 102,000 French adults and their dietary habits found that after about eight years, those who consumed artificial sweeteners, including aspartame, were slightly more likely (1.13 times) to develop cancer than those who didn't.

Artificial sweeteners have also been linked to some weight gain. A 2020 study published in the Journal of the American Heart Association followed 203 adults who had at least one sugary beverage a day and followed them for a year. One group was given artificially sweetened drinks such as Diet Coke and Diet Pepsi and was asked to substitute them for their usual soft drinks. Another group was given shipments of plain and sparkling water, and a third group was asked to keep up their usual pattern of drinking sugary beverages. The researchers found that people who drank artificially sweetened diet drinks gained a pound during the study period, while those who kept drinking sugary beverages gained about 10 pounds and those who drank water and sparkling water lost weight.

A study published in the American Journal of Clinical Nutrition in 2019 compared the effects of sugar and four different low-calorie sweeteners on weight gain in adults who were overweight and obese, and found that people who drank beverages that contained saccharin had "significantly increased body weight" after three months.

A 2018 study published in the journal Molecules found that artificial sweeteners aspartame, sucralose and saccharin may disrupt microbial gut balance (the balance of good and bad bacteria in your gut).

But the data has been mixed. Lab studies on rats have linked high doses of saccharin to the development of bladder cancer in rats, but later studies showed that the way saccharin can cause cancer in rats doesn't apply to humans. As a result, saccharin was originally listed in the U.S. National Toxicology Program’s Report on Carcinogens as a substance reasonably anticipated to be a carcinogen — and later delisted.

A 2019 review of 35 observational studies and 21 controlled trials of the use of artificial sweeteners in children and adults published in BMJ found that there was no evidence that these products impacted adults' eating behaviors, mood or cognition or their likelihood of developing cancer, cardiovascular disease and kidney disease.

Is it safe to use artificial sweeteners?

While the latest study findings are concerning, experts say you shouldn't stress about using artificial sweeteners just yet. "'Genotoxic' means that a substance can potentially damage your DNA," Jamie Alan, an associate professor of pharmacology and toxicology at Michigan State University, tells Yahoo Life. "Keep in mind that we are always receiving DNA insults from the environment. It's the cumulative effect that is concerning."

Registered dietitian Scott Keatley, co-owner of Keatley Medical Nutrition Therapy, tells Yahoo Life that it's tough to draw too many conclusions from the latest study. "The real difficulty is telling how these substances will interact with a complete system like the human body and not cells in a beaker, which is what this new research did, more or less," he says.

However, Deborah Cohen, an associate professor in the Department of Clinical and Preventive Nutritional Sciences at Rutgers University, tells Yahoo Life that for now, "the evidence is compelling," adding: "I would recommend that people significantly limit their consumption of artificial sweeteners and sugar substitutes or avoid them entirely."

She has concerns about the link between artificial sweeteners and gut issues, something that other experts echo. "So much of our body processes happen in the gut, and as our gut microbiome changes, it affects other functions happening in the body," registered dietitian Jessica Cording, author of The Little Book of Game Changers, tells Yahoo Life.

Cording recommends that her patients keep artificial sweetener use "to a minimum." Among other things, she notes that these products taste incredibly sweet — sucralose is about 600 times sweeter than table sugar, for example — and says that can cause people to crave sweet things more than they would if they hadn't used artificial sweeteners.

But Colleen Rauchut Tewksbury, a registered dietitian and adjunct associate professor at Penn Medicine, tells Yahoo Life that there's still a lot we don't know about how artificial sweeteners impact the body. "For now, the science is too early and not much in humans yet to answer whether or not these are safe and in what amount," she says. "These types of sweeteners are generally recognized as safe, so if someone enjoys them and they help them achieve their health goals, they can be a great option. If someone is concerned specifically about gut health, it may be a good idea to limit consuming nonnutritive sweeteners."

Keatley agrees, saying you don't need to avoid artificial sweeteners entirely, but that it's a good idea to pay attention to how much you're consuming. "Just like anything else, these substances should be used in moderation," he says.

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