The long-running argument over the harms and benefits of artificial sweeteners will be further complicated by new research out this week. The results of a large observational study suggest that higher consumption of artificial sweeteners is linked to a higher risk of cancer. Importantly, though, this sort of data cannot show a direct cause-and-effect relationship between the two, only a correlation.
The study was conducted by researchers in France, primarily from the nutritional epidemiology research team based at Sobonne Paris Nord University. They analyzed data from the NuriNet-Santé project, a population study that has been following the health and lifestyle habits of French adults since 2009, largely through questionnaires filled out online. They focused on over 100,000 volunteers who had regularly completed 24-hour dietary diaries, using them as a proxy for their typical level of artificial sweetener consumption. They were then able to track the later health outcomes of these volunteers over a median length of eight years through linked electronic health records.
Overall, people estimated to consume the highest amount of sweeteners had a modest but noticeably higher risk of developing any cancer when compared to non-consumers—13% higher. This associated risk was greatest for those who consumed aspartame and acesulfame-K. And among specific cancers, the risk was highest for breast cancer and other cancers thought to be related to obesity, such as colorectal, stomach, and liver cancer.
“These results suggest that artificial sweeteners, used in many food and beverage brands worldwide, may represent a modifiable risk factor for cancer prevention,” the authors wrote in their paper, published Thursday in PLOS Medicine.
There has been a long, complicated debate over the health impacts of artificial sweeteners, which are meant to be no or low-calorie alternatives to sugar. Most famously, a study in rats by a team of researchers in Italy published in 2005 found a possible increased risk of cancer. But that study and subsequent work by the same team have been fiercely criticized by other scientists, partly for the unrealistically large doses the rats were given and partly because the rats may not be a good proxy for people. Overall, the data on whether artificial sweeteners are harmful to humans in any way has been decidedly mixed. Currently, the Food and Drug Administration considers sweeteners such as aspartame to be “safe for the general population,” with the clear exception of those with the rare condition phenylketonuria, who cannot easily metabolize a component of aspartame.
No single study should be seen as overwhelming evidence for a hypothesis, and this type of research is rarely seen as a smoking gun, since it can only show a correlation between eating artificial sweeteners and a higher cancer risk. The scientists even note that there are other possible explanations for the connection seen in their research. For instance, it’s possible that people who are already more susceptible to cancer for other reasons are more likely to switch to drinking diet sodas or other products containing artificial sweeteners.
That said, the authors say they tried to account for these known issues by running different analyses of the data, and they still found a clear link. And their math in general was adjusted for many possibly confounding factors like body mass index, age, physical activity, smoking, and other dietary choices.
They note that the European Union’s European Food Safety Authority is in the middle of conducting a re-evaluation of the safety of artificial sweeteners (along with all other food additives). And while the findings may not be the final word, they argue that their work should provide “important and novel insights” to that re-evaluation by EFSA and other relevant health agencies.