Sucralose, a widely used zero-calorie sugar substitute, may not be safe for cancer patients undergoing immunotherapy. A new study by researchers at the University of Pittsburgh and UPMC Hillman Cancer Center, published on July 31 in Cancer Discovery, reports that high consumption of sucralose is linked to poorer treatment response and reduced survival in patients with melanoma and non-small cell lung cancer.
High Sucralose Intake Impairs Immunotherapy Effectiveness
Analyzing data from 132 patients receiving immune checkpoint inhibitor therapies (such as anti-PD1), the research team found that individuals who regularly consumed high amounts of sucralose through diet sodas, coffee, or tea had a significantly weaker immune response and worse survival outcomes than those who consumed little to none.
Lead author Dr. Abby Overacre, assistant professor of immunology at Pitt and UPMC Hillman Cancer Center, explained,
“It’s easy to say, ‘Stop drinking diet soda,’ but cancer patients are already overwhelmed. We wanted to find a solution that doesn’t require a drastic diet change.”
Mouse Models Reveal Gut Microbiome Disruption
To investigate the mechanism behind this effect, the team conducted mouse model experiments. They discovered that sucralose altered the gut microbiome, promoting bacterial strains that break down arginine, a key amino acid essential for T cell function.
When arginine levels dropped, T cells lost their ability to attack cancer cells, significantly undermining the effectiveness of immunotherapy. Mice fed with sucralose developed larger tumors and had lower survival rates during treatment.
Arginine and Citrulline Supplements Reverse the Effect
Importantly, the researchers found a potential solution. Supplementing the diet with arginine or citrulline (a compound that converts to arginine in the body) restored immunotherapy response in sucralose-fed mice. This approach successfully reversed tumor growth and improved survival outcomes.
“Arginine is crucial for T cell function, especially in cancer,” said Overacre. “When sucralose-driven microbiome changes deplete arginine, T cells become ineffective. But supplementing arginine reactivates the immune response.”
Clinical Implications and Future Trials
The study’s findings prompted researchers to explore how to translate these insights into clinical care.
Senior author Dr. Diwakar Davar, associate professor of medicine and oncologist at UPMC Hillman, noted,
“Sucralose impeded immunotherapy across different cancer types, stages, and treatment methods. These results suggest we can develop targeted prebiotics or nutrient-based interventions for patients who consume artificial sweeteners.”
As reported by medschool.pitt.edu, the team now plans to launch a clinical trial to test whether citrulline supplementation can enhance antitumor immunity and modulate the gut microbiome in cancer patients. They also intend to examine other popular sugar substitutes—aspartame, saccharin, xylitol, and stevia—for their potential impact on the immune system and cancer treatment efficacy.
Balancing Nutrition and Treatment in Cancer Care
This research highlights the critical link between diet, gut health, and immunotherapy response. While sucralose may offer benefits for calorie control or blood sugar management, its potential to disrupt immune function during cancer treatment warrants further investigation. The study underscores the importance of personalized nutrition strategies in supporting cancer therapies and improving outcomes.