There are different forms of sugar, with the most talked about being a single molecule called glucose, the primary fuel for all cells in the body. Any food containing carbohydrates (CHOs) contains glucose and other forms of sugar, but not all CHO-containing foods are made equal. Complex CHOs from whole foods, such as vegetables, fruits, and whole grains, and simple CHOs from processed sugars and processed grains, such as white rice and white flour, have very different effects on human health.
The idea that sugar could fuel the growth of cancer cells mainly comes from Warburg’s Effect on cancer cells’ enhanced conversion of glucose to pyruvate, followed by lactate formation even in the presence of abundant oxygen. (Vaupel et al., 2019) The subsequent modern-day analysis of cancer as a metabolic disease was attributed to Thomas Seyfried, who concluded that glucose and glutamine are the two primary fuel sources for tumor cells. (Seyfried & Chinopoulos, 2021; Seyfried & Shelton, 2010)
So instead of fearing that sugar feeds cancer, a genuine concern is whether CHO and glucose are linked with cancer. Before answering that, I’d like first to discuss the ketogenic diet (KD), which has been more and more studied in its effects on managing and treating cancer patients due to its low CHO macronutrient profile. While limited studies have shown its therapeutic effects in conjunction with standard cancer treatments, more studies about KD, especially the safety of its long-term use, still need to be researched. Its clinical application must also be closely supervised by specialized nutritionists/dietitians. Here are the challenges with KD:
KD may contraindicate with specific concomitant medical diagnoses such as type-1 diabetes, liver and/or gallbladder dysfunction, etc.
KD is very challenging to maintain long-term.
All body cells, healthy or cancerous, require glucose to function. Without adequate CHOs, our body will make glucose converted from stored protein and fat, which is the underlying mechanism of KD. If not properly implemented, a very low CHO diet like KD could lead to the breakdown of protein stored in the body, potentially contributing to muscle wasting, malnutrition, and undesired weight loss.
Due to these reasons, KDs may not be suitable or accessible for many cancer patients. So, what does this implicate for those cancer patients who can't restrict their CHO intake? Here are a couple of crucial points to understand:
As I mentioned earlier, there is a vast difference between complex CHOs and simple CHOs. Complex CHOs from wholefood-based vegetables and fruits contain a lot of fiber and a wide array of vitamins, minerals, phytochemicals, and antioxidants. These foods not only result in a better glucose mechanism but also possess cancer-fighting effects. On the other hand, refined simple CHOs from refined sugar and processed grains can contribute to excess body fat, unwanted weight gain, and spiked blood insulin and glucose levels, all of which can contribute to cancer cell growth. Emerging research has shown a link between overweight or obese and an increased risk of cancers. (Preuss et al., 2010)
Regarding consuming CHO-containing foods, the glycemic index is another crucial aspect to pay attention to. CHO-containing foods with higher glycemic indexes lead to higher blood glucose levels; therefore, consuming those with lower glycemic indexes is highly recommended.
My Final Thoughts:
A multi-tier approach should be considered, which leads to some crucial questions to think about:
Should overall CHO intake be restricted for cancer patients?
What is the recommended daily CHO intake for cancer patients?
What kind of CHO foods to consume?
To answer these questions, it’s essential to highlight the metabolic basis of cancer. The best example to explain the connection between CHOs/glucose and cancer cell growth is the mechanism of the PET scan, the most used diagnostic procedure for assessing a wide range of cancers. The PET scan was designed based on the tumor’s reliance on glucose for energy, and it’s been the gold standard for cancer diagnosis and imaging for many cancer types. It involves the infusion of a sub-physiological dose of radio-labeled deoxy-glucose. Due to the significantly elevated glycolytic metabolism and glucose affinity, deoxy-glucose gets isolated and trapped within the cancer cells, which the PET scanner can detect. (Berger, 2003; Positron Emission Tomography and Computed Tomography (PET-CT) Scans | Cancer.Net, n.d.)
As for the dietary strategy for managing cancer, I highly recommend a whole-food-based low-glycemic diet primarily comprised of plant foods. This dietary pattern is beneficial for everyone. For cancer patients, I would recommend additional adjustments, including raising the percentage of healthy fat intake and reducing overall CHO intake.
Jenny Noland, MS, CNS, CNGS, CKNS, LDN, MBA
Functional Nutritionist in Eugene, Oregon
Board-Certified Nutrition Specialist
Board-Certified Nutritional Genomics Specialist
Board-Certified Ketogenic Nutrition Specialist
Certified Oncology Nutrition Specialist
Personalized Nutrition Therapy for Metabolic Dysfunction and Cancer Care
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