This article explains how excess sugar can fuel cancer spread and why sucralose may interfere with the body’s response to cancer treatment.
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Este artículo explica cómo el exceso de azúcar puede impulsar la metástasis y por qué la sucralosa podría interferir con la respuesta al tratamiento contra el cáncer.
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Introduction
Most people know that eating too much sugar is bad for their waistline. But fewer realize that sugar—and even some artificial sweeteners—can also play a role in how cancer develops and how it responds to treatment.
Recent research has revealed two troubling patterns. First, sugar-sweetened drinks that contain both glucose and fructose don’t just increase the risk of getting colorectal cancer—they can actually make existing tumors more aggressive, fueling their ability to spread to other organs.
Second, sucralose—the common “zero-calorie” sweetener found in many diet sodas and sugar-free products—may interfere with the body’s ability to fight cancer. By altering the gut microbiome and depriving immune cells of the essential nutrients they need, sucralose has been shown to blunt the effects of cutting-edge cancer immunotherapy.
Together, these findings point to a simple but powerful message: avoiding excess sugar matters not only for cancer prevention but also after a diagnosis. Whether through natural sugar or artificial substitutes, what you drink and eat can tip the balance in favor of cancer—or against it.
Sugar and Cancer: What the Evidence Shows
Epidemiological Clues
Large population studies consistently link high sugar consumption—especially from sugar-sweetened beverages (SSBs)—with an increased risk of cancer. For example, women who drank one or more sugary drinks per day had a significantly higher risk of developing liver cancer compared to those who rarely consumed them (Wang et al., JAMA Network Open, 2022).
Similarly, men with the highest intake of sugary beverages showed about a 20% higher risk of prostate cancer in a recent review (Cancer Epidemiology, 2025).
Beyond site-specific cancers, high added sugar intake has been associated with greater overall cancer incidence and mortality.
In the PREDIMED cohort, each additional 5 grams of sugar from liquid sources was linked with an 8% higher risk of cancer and cancer-related death (Papandreou et al., Clinical Nutrition, 2021).
Sugar and Cancer
Why might sugar play such a role? Several biological pathways help explain the association:
- Fuel for Tumors: Many cancers thrive on glucose through aerobic glycolysis, also known as the Warburg effect. Excess circulating sugar gives tumors a ready energy supply.
- Insulin and IGF-1 Signaling: High sugar intake promotes insulin resistance and elevated IGF-1, both of which stimulate cell growth and inhibit apoptosis, creating a cancer-friendly environment.
- Inflammation and Oxidative Stress: Diets rich in refined sugar promote chronic, low-grade inflammation, which fosters DNA damage and initiates tumors.
- Fructose Metabolism: Research shows fructose from sugary drinks doesn’t just supply calories; it can be converted into sorbitol and lipids that cancer cells use to metastasize.
More Than Obesity
It’s tempting to dismiss the sugar–cancer link as simply an effect of weight gain. While obesity is an important risk factor, the evidence shows sugar can act independently.
In mouse models, sugar-sweetened beverages directly promoted colorectal tumor growth even without obesity, suggesting a more direct cancer-promoting effect.
Sugary Drinks and Colorectal Cancer Spread
A 2025 study in Nature Metabolism delved deeper into how sugary drinks can exacerbate the risk of colorectal cancer.
Researchers tested the effects of glucose and fructose—the two main sugars in soda, fruit punches, and other sweetened drinks—on colorectal cancer cells and in mice.
What They Found
- When cancer cells were exposed to both glucose and fructose together (as in high-fructose corn syrup or table sugar), the cells became more mobile and invasive, key steps in forming metastases (the spread of cancer to other organs).
- In mice with colorectal cancer, those given sugary water developed significantly more liver metastases compared to mice that received plain water or glucose alone.
- The primary tumor did not get larger with sugar, but its ability to spread to the liver increased—showing that sugar fuels cancer spread, not just growth.
The Mechanism: A Sugar Shortcut
The study showed that cancer cells used an enzyme called sorbitol dehydrogenase (SORD) to process fructose into sorbitol.
This reaction shifted the balance of cell energy molecules (NAD⁺/NADH), which then supercharged glycolysis (the breakdown of sugar) and activated the mevalonate pathway, a system linked to cell growth and metastasis. Fructose and glucose are derived from sugar.
Importantly, colorectal cancer tumors from patients were found to have higher SORD levels compared to normal tissue, suggesting that this mechanism is active in real human cancers—not just in lab models.
Why This Matters
This finding highlights the urgency of public health concerns about sugary drinks. It’s not just about gaining weight or developing diabetes. For people with colorectal cancer, consuming sugary beverages may directly increase the risk of the cancer spreading to vital organs like the liver.
While sugary drinks help cancer cells become more aggressive and spread, the story doesn’t end there. Many people who cut back on sugar turn to artificial sweeteners as a “safer” choice.
But new research suggests that one of the most common sugar substitutes, sucralose, may also pose serious risks for people with cancer—this time not by feeding the tumor directly, but by weakening the immune system’s ability to fight back.
Sucralose, the Gut Microbiome, and Immunotherapy
What the Research Found
While sugar can help cancer spread, a new study shows that sucralose—the artificial sweetener found in many “sugar-free” drinks and foods—may also be harmful for people with cancer. In both mice and human cancer patients, high sucralose intake made immunotherapy treatments less effective.
Immunotherapy, especially immune checkpoint inhibitors like anti-PD-1 drugs, works by activating the body’s own T cells to attack tumors. However, when animals or patients consumed sucralose, their gut microbiome changed in harmful ways.
This shift reduced the availability of arginine, an amino acid essential for T cells to remain energized and effective. Without sufficient arginine, T cells become exhausted, tumor growth accelerates, and immunotherapy fails to function properly.
Key Details
- In cancer patients with melanoma and lung cancer, those who reported higher sucralose intake had lower treatment response rates and shorter survival compared to those with little or no sucralose intake.
- In mouse models, tumors grew faster and resisted anti-PD-1 therapy when the animals were given sucralose in their drinking water.
- Importantly, when researchers restored arginine or transferred a healthy microbiome, the effectiveness of immunotherapy returned.
The Takeaway
Sucralose doesn’t directly cause cancer, but it may quietly undermine one of the most powerful modern cancer therapies by disrupting the gut–immune system connection. For patients undergoing immunotherapy, avoiding sucralose could help their treatments work better.
Synthesizing the Message: “Sugar Before, Sucralose After — Both Risks”
Taken together, these studies show that both natural sugars and sucralose can create major problems for people facing cancer—but in very different ways.
Before diagnosis and in early cancer
High intake of sugary drinks can set the stage for cancer growth and even make existing tumors more aggressive. By boosting enzymes like SORD, glucose and fructose together help colorectal cancer cells invade and spread to vital organs like the liver.
For people not yet diagnosed or those in the early stages of disease, avoiding excess sugar may lower the risk of cancer progression.
After diagnosis and during treatment
Patients who switch from sugar to “diet” drinks may think they are making a safe choice, but sucralose poses its own danger. By disrupting the gut microbiome and starving T cells of essential nutrients, sucralose can blunt the body’s ability to respond to immunotherapy.
This means that even the most advanced treatments can be compromised by what appears to be a harmless sugar substitute.
The Bottom Line
Cancer patients and those hoping to prevent cancer should see diet as part of the treatment plan. Avoiding excess sugar before cancer can lower the chance of developing or worsening disease.
After diagnosis, avoiding sucralose and other artificial sweeteners may help ensure that therapies, such as immunotherapy, work as intended.
In short, sugar feeds the tumor, and sucralose weakens the defense. Choosing whole, unsweetened foods and beverages is one of the simplest steps patients can take to give themselves the best chance, before and after cancer.
Practical Steps for Everyday Life
Limit Sugary Drinks
- Cut back on sodas, fruit punches, and other sugar-sweetened beverages.
- Even juices labeled “natural” can contain high amounts of added sugar. Choose water, sparkling water, or unsweetened tea instead.
Be Careful with Artificial Sweeteners
- Sucralose (often found in “sugar-free” sodas, baked goods, and packets like Splenda) may interfere with cancer treatments like immunotherapy.
- If you need a sweetener, consider using small amounts of natural options such as stevia or monk fruit. Evidence on these is still limited, but so far they don’t appear to have the same risks as sucralose.
Choose Whole Foods
- Focus on foods that are naturally low in added sugar: vegetables, whole fruits, legumes, nuts, and whole grains.
- Protein-rich meals with fiber can help stabilize blood sugar levels and reduce insulin spikes that may feed tumor growth.
Support Your Gut and Immune System
- Eat a diet rich in fiber (from beans, oats, fruits, and vegetables) to nourish healthy gut bacteria.
- Avoid excessive processed foods and ultra-sweetened snacks that can disturb your microbiome balance.
Work With Your Care Team
- If you are receiving chemotherapy or immunotherapy, ask your doctor or dietitian about how your food and drink choices might affect treatment.
- Nutrition is not a replacement for therapy, but it can be a powerful partner.
Conclusion
Sugar and artificial sweeteners often seem like simple choices at the grocery store, but research shows they can have serious consequences for cancer risk and treatment. Sugary drinks may not just raise the chance of developing colorectal cancer—they can also make existing tumors more likely to spread.
Sucralose, once thought to be a harmless substitute, may reduce the effectiveness of advanced therapies by weakening the immune system through changes in the gut microbiome.
The message is clear: what you drink matters before and after a cancer diagnosis. Cutting back on excess sugar can lower long-term risk, while avoiding sucralose during treatment may help preserve the body’s best defenses.
Choosing whole, unsweetened foods and beverages is a small but meaningful step toward better outcomes.
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References:
- Feng, Tianshi, et al. “Fructose and Glucose from Sugary Drinks Enhance Colorectal Cancer Metastasis via SORD.” Nature Metabolism, 2025. https://www.nature.com/articles/s42255-025-01368-w
- Morder, Kristin M., et al. “Sucralose Consumption Ablates Cancer Immunotherapy Response through Microbiome Disruption.” Cancer Discovery, 2025. https://aacrjournals.org/cancerdiscovery/article/doi/10.1158/2159-8290.CD-25-0247/763776/Sucralose-consumption-ablates-cancer-immunotherapy
- Papandreou, Carmen, et al. “Consumption of Sugars and Risk of Cancer in the PREDIMED Trial.” Clinical Nutrition, vol. 40, no. 9, 2021, pp. 5556–64. https://pubmed.ncbi.nlm.nih.gov/34536637/.
- Wang, Long-Gui, et al. “Sugar-Sweetened Beverage Consumption and Risk of Liver Cancer and Chronic Liver Disease Mortality in US Women.” JAMA Network Open, vol. 5, no. 8, 2022, e2222246. https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2795053
- Discacciati, Andrea, et al. “Sugar-Sweetened Beverages and Risk of Prostate Cancer: A Systematic Review and Meta-Analysis.” Cancer Epidemiology, vol. 87, 2025, 102452. https://doi.org/10.1016/j.canep.2025.102452.
- National Cancer Institute. “Study Reveals How Fructose May Fuel Tumor Growth.” Cancer Currents Blog, 2025. https://www.cancer.gov/news-events/cancer-currents-blog/2025/fructose-tumor-growth-liver-lipids
- American Institute for Cancer Research. “The Sugar-Cancer Connection.” AICR, 2020. https://www.aicr.org/news/the-sugar-cancer-connection/.
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