A “sticky” and common, question from patients and their family members is about sugar and cancer – Does sugar feed cancer? The short answer is: “yes, cancer is a metabolic disease; but there is more to the story than that.”
*Vocabulary note to the reader:
“Glucose” is one type of dietary sugar. Dietary sugars are also referred to as carbohydrates.
First, we need to recognize that every cell in our body utilizes glucose for fuel. Glucose is even an obligatory (required) fuel source in the adult brain. If you were to stop eating any carbohydrates or sugars in your diet, your body would still convert at least a small amount of fat and protein into glucose. Dietary sugar or carbohydrates can be very healthy when they come from whole-food sources, as part of a balanced diet. Where it gets a little more interesting is in recognizing the following:
Tumor cells will uptake sugar at a faster rate than healthy cells. If you’d like to watch cancer cells uptake sugar at this faster rate, take a look at a Positron Emission Tomography scan (PET Scan) in a patient with an active cancer. During a PET scan, a patient is injected with F-18 fluorodeoxyglucose, or FDG, a radioactive glucose analog. Cancer is identified when cancer cells uptake this radioactive sugar-like substance at a faster rate than healthy or benign cells. This is because malignant tumors are generally more metabolically active1. They also often have more insulin receptors on their surface to facilitate glucose uptake as well2.
Different dietary carbohydrates can have a different impact. Glycemic index is a relative ranking of carbohydrate content, according to how a food affects blood glucose levels. Lower glycemic index foods, and fiber containing carbohydrates, are digested, absorbed and metabolized at a slower rate. Simple sugars and high glycemic index foods can increase blood sugar and insulin which are associated with cancer risk3.
What about fruit?
Although fruit contains fructose, it is a whole food with fiber, vitamins, minerals and other nutritive benefits. Outside of specific medically needed low carb, keto-adapted or ketogenic diets, there is generally no need to limit a reasonable daily intake of fruit or berries. However, patients may want to avoid excessive intake of tropical fruits which have a higher glycemic index.
Higher levels of blood sugar can inhibit anti-tumor responses of the immune system4. The immune system is supposed to recognize cancer cells, find and destroying them. Natural killer cells are one type of immune cell involved in this process. Studies show that type 2 diabetes is associated with alterations in natural killer cells, leading to impairment in their cancer killing ability, increased cancer risk and a higher incidence of cancer5.
High blood sugar can lead to systemic inflammation and oxidative stress. The tumor microenvironment (area around a tumor) is largely impacted by inflammation. While acute inflammation is helpful for the body to recover from trauma, illness or infection, chronic inflammation is associated with cancer and chronic disease. Specifically, chronically elevated glucose may cause oxidation and damage to tissues and is associated with chronic inflammatory diseases, carcinogenesis (cancer development), increased tumor growth and metastatic disease6.
Cancer has been recognized as a metabolic disease for over a century7. While 5-10% of cancer case are estimated to be caused by inherited genetics, the vast majority of cancer is a result of our environment (diet, lifestyle, exposures, experiences, etc.) interacting with our genetics. Negative effects on our genetic expression can be a result prior disturbances of cellular energy metabolism7,8,9. Clinical research supports this observation:
- People who have elevated blood sugar levels have a heightened risk for cancer10.
- People with diabetes, obesity or metabolic syndrome, have a higher risk for cancer and cancer-related death3,5,10.
- Elevated insulin levels are a risk factor for cancer recurrence11.
- Insulin like growth factor-1, a growth factor made when insulin levels increase, is linked to growth and recurrence risk in some cancers12.
- Metformin, an anti-diabetic drug, is associated with improved survival outcomes in some cancers13.
- Exercise and intermittent fasting are currently being investigated as strategies to reduce recurrence risk. Their value may at least in part be due to the improved regulation of blood sugar and insulin14,15.
Elevated blood sugar can certainly play a role in cancer and chronic disease. Fortunately, you have control over your diet, timing of food intake, exercise, stress management use of naturopathic medicine and use of medications. Patients can improve blood sugar levels and insulin responses and therefore potentially reduce their risk for cancer recurrence.
Simple blood testing to assess blood sugar control may include:
- Hemoglobin A1C: average blood sugar level over past 3 months.
- Fasting insulin: hormone that regulates blood sugar utilization
- IGF-1: a growth factor that is stimulated with insulin production (also with meat intake)
- Fasting glucose: after fasting for 10 hours this measures a single moment value of person’s blood sugar
Some “sweet” strategies aimed at improving blood sugar control could include:
- Reducing or avoiding simple sugars, especially processed and refined sugars like soda.
- Incorporating safe, appropriate and regular exercise your lifestyle.
- Making time for regular sleep and relaxation. Higher cortisol (stress hormone) can elevate blood sugar.
- Adding natural or pharmaceutical therapies to your diet and life-style practices, if indicated. This could include botanical medicines like berberine, nutrients like chromium, medications like metformin or others.
Be sure to talk with your naturopathic doctor or healthcare provider before making changes to your diet or life-style and before starting any natural medicines or supplements. While these therapies are generally well-tolerated, there are contraindications, allergies and drug-drug or drug-herb interactions that should be considered for each individual person.
If you have questions or concerns about your blood sugar control or need testing/support, please reach out to me Sage Clinic, Vancouver.
In Good Health,
Dr. Jessica Moore, ND
Qingke Duan, Hehe Li, Chenggang Gao, Hengqiang Zhao et al. High glucose promotes pancreatic cancer cells to escape from immune surveillance via AMPK-Bmi1-GATA2-MICA/B pathway. J. of Experimental & Clinical Cancer Researchvolume 38, Article number: 192 (2019)
Schwartz L, Seyfried T, Alfarouk KO, Da Veiga Moreira J Out of Warburg effect: An effective cancer treatment targeting the tumor specific metabolism and dysregulated pH. Semin Cancer Biol. 2017 Apr;43:134-138
Emily J. Gallagher and Derek LeRoith. Epidemiology and Molecular Mechanisms Tying Obesity, Diabetes, and the Metabolic Syndrome With Cancer. Diabetes Care 2013 Aug; 36(Supplement 2): S233-S239
Vicente Morales-Oyarvide, Chen Yuan, Ana Babic, Sui Zhang. Dietary Insulin Load and Cancer Recurrence and Survival in Patients With Stage III Colon Cancer: Findings From CALGB 89803 (Alliance). JNCI: Journal of the National Cancer Institute, Volume 111, Issue 2, February 2019, Pages 170–179
Jennifer A. Emond, John P. Pierce, Loki Natarajan, Laarni R Gapuz et al. Risk of Breast Cancer Recurrence Associated with Carbohydrate Intake and Tissue Expression of IGF-1 Receptor