"Sugar-free" might sound healthy, but a new study hints that people who consume a lot of artificial sweeteners may face a slightly higher cancer risk.
Experts stressed that the findings do not prove sugar substitutes are the culprit. But they said it is wise for people to limit not only added sugars, but also the processed foods that carry sugar-free boasts.
The study, of more than 100,000 French adults, found that the roughly one-fifth with the highest intake of artificial sweeteners were 13% more likely than non-consumers to be diagnosed with cancer. The risks were specifically seen with cancers where obesity is thought to play a role - including breast, colon and ovarian cancers.
Over the years, lab research has suggested that artificial sweeteners are capable of promoting cancer - possibly by feeding chronic inflammation in the body, contributing to DNA damage, or affecting the composition of bacteria in the gut.
Meanwhile, some studies have found relatively higher cancer risks among people who regularly consume diet drinks.
The new study appears to be the first to quantify people's intakes of various artificial sweeteners (not just diet drinks) and look at the relationship to cancer risk, according to researchers Charlotte Debras and Mathilde Touvier.
They are both with the French National Institute for Health and Medical Research.
"In this large (study population), artificial sweeteners - especially aspartame and acesulfame-K, which are used in many food and beverage brands worldwide - were associated with increased cancer risk," Debras said.
She noted that the connection to aspartame and acesulfame-K, specifically, may simply reflect the fact that they were the most commonly consumed sweeteners. And the study cannot prove that any sugar substitute directly contributes to cancer.
But the researchers did dig into many possible alternative explanations: People who consume a lot of artificial sweeteners may weigh more, be more likely to have diabetes, or eat fewer fruits and vegetables, for instance.
After those differences were accounted for, high intake of artificial sweeteners was still tied to a modest increase in cancer risk, the investigators found.
In a written statement, a group representing the sweetener industry said there is "no credible evidence" to suggest that sweeteners cause cancer.
The Calorie Control Council said the new findings contradict "numerous global health organizations who have regarded each of the named sweeteners as safe, following rigorous assessments." Its statement added: "Low- and no-calorie sweeteners are safe and serve as effective tools in weight management, sugar reduction and blood glucose management."
Meanwhile, Marji McCullough, senior scientific director of the American Cancer Society, called the research important.
"It addresses an area of public health interest," she said, praising the study for its "thorough assessment" of the types and amounts of sugar substitutes that people consumed.
It's still possible that other factors, like weight gain, at least partly account for the findings, McCullough noted. But from a health standpoint, she said, it's best for people to strive for plenty of whole foods - including fruits, vegetables and fiber-rich grains - while limiting processed foods, sugar-free or not.
"Some highly processed foods advertised as 'sugar-free' can have very little nutritional value," McCullough said.
Amy Bragagnini is an oncology dietitian with Mercy Health Lacks Cancer Center in Grand Rapids, Mich.
She cautioned that it is challenging to tie something as complex as cancer to one diet component. And she agreed that overall diet quality is key.
Specifically, Bragagnini said, it's helpful for people to think about the healthy foods they can add to their daily life rather than what they will ban. That's what she encourages when working with cancer patients.
"I'll ask, how many fruits and vegetables are you eating every day?" she said. "Let's start there."
Artificial sweeteners can fit into a healthy diet, according to Bragagnini - if, for instance, that one sugar-free cookie satisfies your sweet tooth, or you are replacing a daily sugary drink with a diet version.
Problems can arise, she said, if people overindulge because of the sugar-free label.
The study - published March 24 in the journal PLOS Medicine - included nearly 103,000 French adults who were 42 years old, on average, at the start. Every six months, they answered detailed questions about what they'd eaten over the past 24 hours, for three consecutive days.
Almost 38,000 participants consumed artificial sweeteners. Half were considered "higher consumers" - typically downing 17 to 19 milligrams or more per day.
Over eight years, 3,358 study participants were diagnosed with cancer. And after the researchers accounted for other factors, the group with a higher intake of artificial sweeteners had a 13% greater risk of cancer compared to non-consumers.
Bragagnini encouraged people to be more "intentional" about what they eat - including thinking about what they actually enjoy, and the serving size that will hit the spot.
If a small portion of regular ice cream is satisfying, she said, that's probably a better choice than half a box of sugar-free cookies.
The American Cancer Society has advice on diet and exercise.
Mathilde Touvier, PhD, director, nutritional epidemiology research team, French National Institute for Health and Medical Research and Sorbonne Paris Nord University, Bobigny, France; Charlotte Debras, PhD candidate, French National Institute for Health and Medical Research and Sorbonne Paris Nord University; Amy Bragagnini, MS, RD, oncology dietitian, Mercy Health Saint Mary's Campus, Lacks Cancer Center, Grand Rapids, Mich.; Marji McCullough, ScD, RD, senior scientific director, epidemiology research, American Cancer Society, Atlanta; Calorie Control Council, written statement, March 23, 2022; PLOS Medicine, March 24, 2022, online