A recent report released by the World Health Organization (WHO) has raised concerns about the potential cancer-causing effects of aspartame, an artificial sweetener widely used in diet sodas and other low-calorie food products. According to a committee of 25 international experts, aspartame may “possibly” cause cancer in people, based on a review of “limited evidence.” However, this new classification does not alter the recommended daily intake limit of the sweetener.
Dr. Francesco Branca, the director of the Department of Nutrition and Food Safety at the WHO, emphasized during a press conference in Geneva that occasional consumption of aspartame is not likely to pose a risk to most consumers. The concern lies with “high consumers” of diet soda or other foods containing aspartame. Dr. Branca called for additional research on the subject, stating that the committee had raised a flag regarding potential risks.
In contrast, the U.S. Food and Drug Administration (FDA) expressed disagreement with the WHO’s classification, citing evidence of the safety of aspartame. The FDA stated that the WHO’s classification of aspartame as “possibly carcinogenic to humans” does not imply a direct link to cancer.
The WHO has maintained an acceptable daily intake (ADI) of aspartame at a maximum of 40 milligrams per kilogram of body weight per day for a long time. This means that an individual weighing 60 kilograms (approximately 130 pounds) could consume up to 2,400 milligrams per day, equivalent to around 12 cans of Diet Coke—significantly higher than what most people typically consume.
Although the WHO has not altered the ADI, Dr. Branca recommended moderation in aspartame consumption, particularly for those using it as a means to avoid sugar and control weight. He stated that the benefits of aspartame in this regard are questionable. Notably, the WHO now advises against the use of non-sugar sweeteners for long-term weight management, based on a 2022 review that found no clear consensus on their effectiveness.
Aspartame was approved as a sweetener in the U.S. in 1974 and gained popularity when Coca-Cola introduced it in Diet Coke during the 1980s, promoting its taste through extensive advertising campaigns. However, skeptics and critics have existed throughout, and recent studies have suggested that artificial sweeteners may increase food cravings and affect the microbiome. Furthermore, a few recent studies have indicated potential cancer risks, prompting the WHO to undertake a comprehensive review of all available data.
Two separate WHO committees examined the evidence on aspartame. The International Agency for Research on Cancer classified aspartame as “possibly carcinogenic to humans” (2B), primarily based on “limited” evidence suggesting a potential link to liver cancer. The classification also considered a large French study, the NutriNet-Santé study, published in 2022, which found a 15% increased risk of cancer, including breast and obesity-related cancers, in individuals consuming higher amounts of aspartame.
While the research agency deemed these studies “high-quality,” it acknowledged the possibility that the findings could be attributed to chance, bias, or other variables rather than aspartame itself. Consequently, the evidence for cancer in humans was categorized as “limited” for liver cancer and “inadequate” for other types of cancers.
The Joint Expert Committee on Food Additives (JECFA), another committee reviewing the evidence, concluded that the evidence of an association between aspartame consumption and cancer in humans is not convincing. JECFA pointed to inconsistent evidence and maintained that the acceptable daily intake levels should remain unchanged.
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The FDA echoed this sentiment in its response, stating that it disagreed with the conclusion that aspartame should be classified as a possible carcinogen. The FDA identified significant shortcomings in the reviewed studies and noted that JECFA did not raise safety concerns or change the acceptable daily intake levels.
Scientists have emphasized the need for more long-term research, as the development of cancer after exposure to carcinogens can take decades. Dr. William Dahut, the chief scientific officer at the American Cancer Society, acknowledged the lack of extensive long-term research and the existing gray area resulting from insufficient tracking of aspartame consumption over time. Dahut recommends caution and limiting intake until more definitive studies are available, despite the link between aspartame and cancer being less clear than those associated with obesity and smoking.
The American Beverage Association, representing major companies such as Coca-Cola, PepsiCo, and Keurig Dr Pepper, supported the FDA’s position and stated that the WHO’s decision to maintain the previously established “acceptable daily intake” reaffirms the safety of aspartame.
Regarding the effects of diet soda on weight management, conflicting evidence exists. While the WHO’s analysis suggests limited long-term benefits, some studies have shown that substituting caloric beverages with zero-calorie alternatives can be beneficial. However, experts emphasize that the best beverages for daily consumption remain water, coffee, and tea.
Physician Walter Willett from the Harvard T.H. Chan School of Public Health acknowledges the weak evidence linking aspartame to cancer in humans. Despite the uncertainties regarding long-term consequences, Willett sees a role for diet soda in managing weight and reducing sugar intake. He likens it to a nicotine patch, potentially helpful for transitioning away from dependence but not the optimal long-term solution.
As the discussion surrounding aspartame and its potential health risks continues, further research and comprehensive studies are necessary to ascertain its impact on human health conclusively.
