Can Diet Soda Cause Cancer?

What's Inside Diet Sodas?

Look around the beverage counter at groceries and restaurants. You will likely see the word diet being labeled on many drink options. These types of beverages do not include the sugar we normally eat today, but artificial sweeteners. As people grew wearier of the quality of the unhealthy ingredients in drinks they consume each day, artificial sweeteners became popular as alternatives to added sugars (Debras et al. 2022). The most widely used artificial sweetener around the world is aspartame, which was invented by James M. Schlatter in 1965 (Czarnecka et al. 2021). Aspartame is used in more than 6,000 food types around the globe, with around 86% of all aspartame added to diet sodas (Soffritti 2024). Within a 1L bottle of diet Coca-Cola, there is approximately 930 mg/L of aspartame being added (Schernhammer et al. 2012). Nowadays, many people drink diet soda to reduce their sugar intake. However, is consuming artificial sweeteners really the healthier choice for your body?

Artificial Sweetener: Aspartame 

Aspartame, which consists of two amino acids L-phenylalanine and L-aspartic acid, is approximately 200 times sweeter than added sugar (Soffritti 2024). While keeping this sweet taste like regular sodas, this artificial sweetener has zero calories. When the human digestive system breaks down aspartame, the artificial sweetener releases methanol, aspartic acid, and a large amount of phenylalanine. In moderate to high amounts these chemicals are dangerous for the body to absorb. Methanol can form formaldehyde and formate, which are toxic to the liver and brain cells. At the same time, the methanol digestion process causes protein denaturation and enzymatic changes through the formation of superoxide anions and hydrogen peroxide. This may also result in physiological changes that cause functional problems in the body (Czarnecka et al. 2021). For example, you may feel a headache and dizziness in your brain after drinking diet soda. So, exactly how dangerous is it for humans to consume artificial sweetener in diet coke?

Aspartame Influence on Cancer Development

Surprisingly, this question was discussed in the 1970s. However, there was not a clear result to this controversial topic. The GD Searle pharmaceutical producer industry conducted three different experiments on whether aspartame is carcinogenic, or cancer-inducing (Soffritti 2024). The research used two groups of rats and one group of mice of different populations. They were treated with different amounts of aspartame each day. For all three experiments, the data showed that there was not a great difference in whether various types of cancer tumors appeared. However, due to possible inaccuracies in experimental design and final statistics, their results were later contradicted by a Japanese group and the US National Toxicology Program (Soffritti 2024).

A 2022 study showed that taking artificial sweetener directly increases cancer risks (Debras et al. 2022). The research involved 102,865 adults from France, who were asked to consume artificial sweeteners, aspartame and acesulfame-K, and keep 24-hour dietary records. Records were then made on the brand names of the consumed products. After adjusting the initial results to account for biological differences and habitual characteristics, the study then compared the data of non-consumers and higher consumers. Overall, the data found that the consumption of artificial sweetener led to increased cancer risks. In particular, women who were high-consumers had higher chances to have breast cancer and obesity-related cancers. However, there still may be biases due to selection and residual confounding factors in this experiment, leading to uncertainties regarding the results.

More recently in 2024, another research group showed that consuming diet sodas can lead to serious results (Soffritti 2024). Three experiments were conducted on mice and rats using different populations. They were treated with different amounts and concentrations of aspartame to mimic the human daily consumption, which averaged to 20 grams per day for both males and female mice. They studied the mice from 8 weeks old to their natural deaths and found that there was a significant increase in tumor appearance, especially for the mice with the greatest consumption of aspartame concentration. This suggested that the ingestion of artificial sweetener increases the risk of cancer. Therefore, diet soda may influence the development of cancer tumors. However, studies are needed in humans as results found in mice do not always occur in humans.

Conclusion

The studies on diet soda containing aspartame suggest that this artificial sweetener is likely to increase the risk of developing cancer tumors in mice. When people first invented diet soda, the primary purpose was to decrease the sugar intake from beverages. While it may be beneficial in preventing diseases like diabetes, obesity rates, and high blood pressure, diet soda may not be the safest option when considering cancer (Czarnecka et al. 2021).

Just like regular beverages, consuming a little diet soda can give you temporary happiness and be refreshing. However, remember to protect your body from harmful chemicals by regulating the amount of consumption. So, consider drinking other healthier options like tea or just simply water. Next time you walk into a restaurant, be mindful about what you drink.

Written by Wenxu Yao and Edited by Aldrin V. Gomes, PhD

References

Schernhammer, E. S., Bertrand, K. A., Birmann, B. M., Sampson, L., Willett, W. C., & Feskanich, D. (2012). Consumption of artificial sweetener– and sugar-containing soda and risk of lymphoma and leukemia in men and women. The American Journal of Clinical Nutrition, 96(6), 1419–1428. https://doi.org/10.3945/ajcn.111.030833 

Debras, C., Chazelas, E., Srour, B., Druesne-Pecollo, N., Esseddik, Y., Szabo de Edelenyi, F., Agaësse, C., De Sa, A., Lutchia, R., Gigandet, S., Huybrechts, I., Julia, C., Kesse-Guyot, E., Allès, B., Andreeva, V. A., Galan, P., Hercberg, S., Deschasaux-Tanguy, M., & Touvier, M. (2022). Artificial sweeteners and cancer risk: Results from the NutriNet-Santé population-based cohort study. PLOS Medicine, 19(3). https://doi.org/10.1371/journal.pmed.1003950 

Morando Soffritti. (2024). UNDERSTANDING the LINK BETWEEN ASPARTAME and CANCER. Expert Review of Anticancer Therapy, 24(9), 793–802. https://doi.org/10.1080/14737140.2024.2383675 

Czarnecka, K., Pilarz, A., Rogut, A., Maj, P., Szymańska, J., Olejnik, Ł., & Szymański, P. (2021). Aspartame—True or False? Narrative Review of Safety Analysis of General Use in Products. Nutrients, 13(6), 1957. https://doi.org/10.3390/nu13061957