The findings drew attention because they pointed to a possible link between daily consumption of diet drinks and certain blood diseases. Across all participants, even a single drink a day was associated with a higher relative risk of leukemia. Among men alone, an association was also found with an increased risk of multiple myeloma and non-Hodgkin lymphoma. However, the results did not repeat themselves in the same way among women, and some of the associations were statistically borderline. Even so, these findings certainly raised concern and justified the additional studies presented below.
The figures that emerged from the study were:
Concern surrounding aspartame did not begin with studies on humans. Studies in rats had already produced findings that raised questions about prolonged exposure to the sweetener. In one of the largest studies of its kind, conducted in 2006, rats that received aspartame for most of their lives showed a reported increase in several types of tumors, including lymphomas and leukemias. Another study, in which exposure began during pregnancy and continued throughout the animals' lives, also found an increase in several types of tumors.
These findings sound alarming, but they are not without problems. Various health bodies and researchers have pointed to limitations in the design of the experiments, difficulties in interpreting the results, and the possibility that other diseases influenced the diagnoses. These studies should therefore not be ignored, but neither should they be presented as proof that aspartame necessarily causes cancer in humans.
In recent years, several large studies have revived concern about a possible link between aspartame consumption and various types of cancer. A large American study published in 2026 that followed some 100,000 adults found that aspartame consumption was associated with a moderate increase in overall cancer risk, and in particular in cancers linked to obesity and the digestive system. The French NutriNet-Santé study from 2022, which included more than 102,000 participants, found a link between higher aspartame consumption and an increased risk of breast cancer and several obesity-related cancers. In addition, a comprehensive 2023 assessment by the International Agency for Research on Cancer pointed to evidence of a possible link between aspartame and hepatocellular carcinoma, the most common type of liver cancer.
As noted, it was in light of these and other findings that aspartame was classified as "possibly carcinogenic to humans", even though the classification does not determine that consuming it necessarily causes disease. It is important to remember that all the human studies were observational, so they can point to a statistical association but cannot prove that the sweetener itself caused the cancer. Even so, the accumulation of several warning signs justifies moderate consumption and continued research, rather than treating aspartame as an ingredient that can be consumed without limit.
Aspartame is not found only in diet drinks. It may appear in a variety of products labeled "sugar-free", "diet" or "reduced calorie", though it is important to know that not every such product necessarily contains it. Many manufacturers now use other sweeteners as well, so the surest way to identify it is to check the ingredient list and look for the name "aspartame" or the designation E951.
Image sources: Vox Efx, Steve Snodgrass
