Sage Advice Blog

Diet Soda: Anti-Cancer Supplement?

August 9, 2018

Alex Speers ND, MS


Two weeks ago, a new study was published that made a lot of headlines in the world of oncology. The study suggested that for patients with colon cancer, drinking diet soda could decrease their risk of cancer recurrence and their risk of dying from colon cancer. As a naturopathic doctor who is always trying to steer patients toward more whole foods, these findings came as a bit of a shock. Could the next big anti-cancer diet craze really be carbonated water with a sprinkling of aspartame and a dash of caramel color? The results didn’t seem believable, but before we get ahead of ourselves, let’s break down the study first.


The study included over 1,000 patients with stage III colon cancer. Stage III means that the cancer has spread beyond the colon and into the lymph nodes, but has not yet invaded any distant organs, like the liver or the lungs. The 5-year survival rate for stage III colon cancer can be anywhere from 53% to 90%, depending on the number of lymph nodes involved. The patients were enrolled in a clinical trial where they were receiving various regimens of chemotherapy to see which regimen was better. In addition, each patient filled out a dietary questionnaire at various points during the trial.


When researchers analyzed these dietary questionnaires after a few years, they found that patients who drank at least one 12-ounce serving of an artificially sweetened beverage every day had a 46% decreased risk of cancer recurrence or cancer-related death compared to patients who didn’t regularly drink these types of beverages. These findings persisted even after researchers controlled for factors such as BMI, physical activity, Western pattern diet, and dietary glycemic load. This is an important step in the analysis because, for example, it could be that people who drink diet soda are more likely to be physically active and therefore the survival benefits are really a result of the physical activity, and not the diet soda. By controlling for factors like this, the researchers strengthen their findings.


So, what’s the catch? Should patients with colon cancer rush out to the store and start loading up on 12-packs of Diet Coke? Probably not. First, this was an observational study, which means that there was no intervention. The researchers did not ask one group of patients to drink a specified amount of diet soda and one group of patients to avoid diet soda. The researchers simply let the patients drink whatever they wanted to and observed them. This is important because it means we are relying on the patient’s memory to accurately document how much diet soda they drank. This could introduce information bias into the study if the patients’ memories are not perfect (and they’re not). Second, because it’s an observational study, there are a lot of potential confounding factors. While the researchers attempted to control for several important factors like physical activity, it’s possible there are other factors they didn’t consider or that their methods didn’t adequately account for these factors. This is called confounding bias. Third, other observational studies have found that drinking artificially-sweetened beverages is associated with an increased risk of stroke, dementia, and type 2 diabetes, suggesting caution before thinking of these drinks as a healthy alternative to regular soda. Lastly, and this is the most important finding, the researchers found that half of the anti-cancer benefit associated with diet soda intake was attributable to patients replacing sugar-sweetened beverages with artificially sweetened beverages. In other words, it may be less about drinking diet soda and more about avoiding sugary drinks.


Patients often get hung up on the idea of SUGAR FEEDS CANCER and as a result, become focused on eliminating any source of sugar in their diet. SUGAR FEEDS CANCER is technically true in that cancer cells use glucose for fuel and have an increased need for fuel because they are rapidly dividing, but it is also true that sugar feeds our healthy cells and that our liver has the capacity to make glucose when levels are low, a process called gluconeogenesis. In addition, not all sugar sources are created equal; fruits, which have higher amounts of sugar, will always be an important part of an anti-cancer diet due to their various nutrients and phytochemicals. Significantly reducing the amount of refined sugar in the diet however, as is found in soda and other processed sweets, is a healthy choice for any patient with cancer and based on this study, may potentially lead to improved survival in the case of colon cancer. As for specifically replacing a patient’s soda intake with diet soda? Until there’s proof of an anti-cancer mechanism for aspartame or caramel color, I’ll likely hold off with a diet soda recommendation.


Guercio BJ, Zhang S, Niedzwiecki D, et al. Associations of artificially sweetened beverage intake with disease recurrence and mortality in stage III colon cancer: Results from CALGB 89803 (Alliance). PLoS One. 2018;13(7):e1099244.


DISCLAIMER: These statements have not been evaluated by the Food and Drug Administration. There are no financial ties to any supplement companies, pharmaceutical companies, or to any of the products mentioned in this post. This post is not meant to treat, cure, prevent, or diagnose conditions or diseases and is meant for educational purposes. As always, please consult your doctor before trying any new treatments or supplements.

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