As a passionate Certified Nutritionist, I am deeply committed to researching and uncovering the popular myths that surround diet and disease. The world of nutrition can be overwhelming, especially when misinformation spreads quickly through media and social circles. My goal is to bring clarity to these topics, especially as they relate to serious health conditions such as cancer.
By the time this blog is published, I will have delivered a presentation on nutrition in cancer care, where I discussed how diet can influence cancer prevention, treatment, and recovery. In preparing for this talk, I remained observant to the fact that this whole topic was not in my particular area of expertise; however, equipped with the critical mindset learned from my time at Mac Nutrition University, I was compelled to delve deeper into common claims about sugar and the ketogenic diet, which have been touted in some circles as essential to cancer care. My aim is to answer the lingering questions many people have about these topics and, ultimately, to better inform the public with evidence-based insights.
The relationship between sugar, the ketogenic diet, and cancer has been a topic of significant interest and debate. While some claims oversimplify or misrepresent the science, there is genuine research exploring how diet impacts cancer metabolism. Here’s what we know based on current evidence.
Understanding the Warburg Effect
First identified by Otto Warburg in the 1920s, the Warburg Effect describes how cancer cells favour glycolysis, a less efficient process of energy production, even in the presence of oxygen. This metabolic shift enables cancer cells to rapidly generate the energy and molecular building blocks they need to proliferate.
Importantly, while glucose is a key player in this process, it is just one part of a larger metabolic puzzle. Cancer cells don’t rely solely on dietary sugar. Especially in instances whereby dietary sugar is restricted, cancer cells can also metabolise fats, amino acids, and other substrates, highlighting their metabolic flexibility.
Does Sugar Feed Cancer?
The claim that “sugar feeds cancer” is often misunderstood and/or misrepresented. All cells, including healthy ones, use glucose as a primary energy source. Glucose refers broadly to blood sugar derived from carbohydrates, whether from refined sugars, whole grains, or fruits. The idea that avoiding all sugar will "starve" cancer cells and beat cancer into submission is, regrettably, an oversimplification.
What we DO know, and what research shows, is that excessive intake of added sugars and refined carbohydrates can indirectly contribute to cancer risk by promoting obesity, insulin resistance, and chronic inflammation. These factors create a pro-cancer environment but are not direct causes of cancer cell growth.
What About the Ketogenic Diet?
The ketogenic diet, a high-fat, low-carbohydrate eating pattern, aims to shift the body into a state of ketosis, where fat-derived ketones are used for energy instead of glucose. Preclinical studies and early-phase clinical trials suggest that the ketogenic diet might slow tumor growth in some cancers by lowering glucose availability and insulin levels.
However, human data are limited. While small studies have shown promise, larger, controlled trials are needed to determine whether the ketogenic diet improves outcomes or complements standard cancer treatments. Adherence can also be a challenge for patients, and the diet may not be suitable for those with unintentional weight loss or malnutrition, which are common in cancer.
Current Recommendations
Leading cancer organizations, including the World Cancer Research Fund (WCRF), focus on overall dietary patterns rather than specific diets. Their recommendations emphasise:
- Maintaining a healthy weight: Obesity is a known risk factor for multiple cancers.
- Eating a plant-forward diet: A diet comprising 70% whole grains, fruits, vegetables, and legumes support overall health and may reduce cancer risk.
- Limiting added sugars and refined carbohydrates: While not directly linked to cancer growth, these foods contribute to poor metabolic health.
- Avoiding extremes: Radical diets like keto should only be explored under medical supervision, particularly for cancer patients.
These guidelines prioritise evidence-based, sustainable approaches over unproven claims.
The Role of Ongoing Research
Emerging research continues to explore the link between cancer metabolism and dietary interventions. For example:
- Human cohort studies are examining the long-term effects of low-glycemic and ketogenic diets on cancer survival rates.
- Investigations into cancer cell metabolism are uncovering new therapeutic targets, such as blocking enzymes involved in glycolysis.
While some findings are promising, they are not yet definitive, and extreme claims should be viewed critically.
Key Takeaways
- Cancer metabolism is complex, and while sugar is a fuel for cancer cells, it is not the sole driver of their growth.
- The ketogenic diet may hold potential in specific cancer contexts, but its efficacy and safety require further study.
- Balanced, plant-rich diets remain the gold standard for cancer prevention and overall health.
For individuals with cancer, dietary changes should always be made in consultation with a healthcare team, including registered dietitians or certified nutritionists. Supporting overall metabolic health is a more effective approach than demonising individual nutrients.
Further Reading
Warburg, O. (1956). "On the Origin of Cancer Cells." Science, 123(3191), 309-314.Hanahan, D., & Weinberg, R. A. (2011). "Hallmarks of Cancer: The Next Generation." Cell, 144(5), 646-674.
WCRF (World Cancer Research Fund). (2021). "Dietary Recommendations for Cancer Prevention and Management." Available at wcrf.org.
Reynolds, A., et al. (2019). "Carbohydrate Quality and Human Health: A Series of Systematic Reviews and Meta-Analyses." The Lancet, 393(10170), 434-445.
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