Does Sugar Have an Effect on Cancer? Some Frequently Asked Questions

Savor Health

Does sugar have an impact on cancer?  Maybe your sister mentioned it or you heard it from a doctor on TV.  Maybe you learned about how a PET scan works and see how sugar causes tumors to light up.  Maybe you’ve heard of the research studies showing how people with the highest sugar consumption have the highest prevalence of cancer. 

This is the number one question that an oncology registered dietitian is asked. The simple answer is that no, sugar doesn’t cause or worsen cancer directly. Of course, the details are a bit more complex than that. What we do know is that eating too much sugar is not healthful for our bodies and can promote an environment that is more prone to certain chronic diseases. 


Does sugar feed cancer? 

All cells in our body use sugar in the form of glucose for energy. Cancer cells use it quicker since they are dividing more rapidly.1 Sugar, as glucose, feeds our bodies; so if we have cancer, it feeds that, too. However, cutting out sugar won’t starve the cancer and make it go away. We need to maintain normal glucose levels for our bodies to function the way they are supposed to.  Our brains and muscles depend on glucose for energy.


Is sugar simple or complex?  

Sugar is a type of carbohydrate. We eat carbohydrates in many different foods but it is important to distinguish between simple and complex. 

Simple carbohydrates are those that are shorter chained molecules.2 Simple carbohydrates are found in foods like white rice, white pasta, cookies, and candies. They tend to have sweeter taste and generally cause a larger insulin response.2,3  Insulin is the hormone that helps the sugar molecules enter our cells to be metabolized for energy.4 

Complex carbohydrates are longer chained molecules. These carbohydrates usually contain fiber, decreasing our body’s insulin response. Complex carbohydrates include whole grains, vegetables, and fruits. 


How does insulin affect our body

Insulin is the hormone that helps the sugar molecules enter our cells to be metabolized for energy. 5 There are times when the insulin does not work correctly. This causes glucose to remain in the blood, driving the body to release even more insulin.  This is called insulin resistance5.  Insulin resistance has a number of effects on the body, which include the promotion of inflammation. This chronic inflammation is associated with an increased risk of cancer. 10 As a result, there may be a relationship between insulin resistance and cancer; however, it is not clear if insulin resistance causes cancer or impacts survival rates. 5


What actually causes insulin resistance? 

One of the main causes of insulin resistance is fat that we deposit around our waistlines.5 Fat stored in our abdomen produces more markers of inflammation associated with insulin resistance than fat elsewhere in the body.6 What causes us to store fat in our abdominal region? Eating to excess in general, not just excess sugar intake. 


How can you optimize your nutrition during and after cancer treatment? 

  • Maintain a normal body weight 5
  • Eat a plant-based diet5
  • Combine complex carbohydrates (like whole grains, brown rice, or fruits) with healthy fats and proteins 5
  • Exercise moderately several times a week 5
  • Minimize stress7 
  • Get adequate sleep8 



Sugar intake by itself does not cause or worsen cancer.  Excessive sugar intake in the context of an unhealthy diet and lifestyle can promote weight gain and insulin resistance, which causes the body to have more inflammation.9,10 These conditions increase cancer risk.  But the good news is that this can easily be managed by consuming a healthy, well-balanced diet rich in fruits, vegetables, and whole grains and limiting refined sugar, processed foods, and convenience foods.  Check out the information throughout the site on healthy eating, shopping, and plant-based diet recommendations.


Always consult your physician and registered dietitian before making any changes to your diet and before implementing any new dietary recommendations or dietary supplements. 



1. Annibaldi A, Widmann C. Glucose metabolism in cancer cells. Curr Opin Nutr Metab Care. 2010;13:466-470.

2. Insel P, Ross D, Bernstein M, McMahon K. Carbohydrates: simple sugars and complex chains. Discovering Nutrition.  Burlington, MA: Jones and Bartlett, 2015. Page 97.

3.  Carbohydrates and blood sugar. Harvard School of Public Health. Accessed December 6, 2016.

4. Wax E. Complex carbohydrates. Medline Plus. 2016. Accessed December 6, 2016.

5. Sugar and Cancer. Oncology Dietetic Practice Group. Accessed December 6, 2016.

6. Castro AVB, Kolka CM, Kim SP, Bergman RN. Obesity, insulin resistance and comorbidities –mechanisms of action. Arq Bras Endocrinol Metabol. 2014;58(6):600-609.

7. Yudkin JS, Kumari M, Humphries SE, Mohamed-Ali V. Inflammation, obesity, stress and coronary heart disease: is interleukin-6 the link? Atherosclerosis. 2000;148:209-214.

8. Spiegel  K, Knutson K, Leproult R, Tasali E, Cauter EV. Sleep loss: a novel risk factor for insulin resistance and type 2 diabetes. 2005;99:2008-2019.

9.  The sugar-cancer connection. American Institute for Cancer Research. Accessed December 6, 2016.

10. Jung UJ, Choi M-S. Obesity and its metabolic complications: the role of adipokines and the relationship between obesity, inflammation, insulin resistance, dyslipidemia and nonalcoholic fatty liver disease. Int J Mol Sci. 2014;15:6184-6223.

The health information contained herein is provided for educational purposes only and is not intended to replace discussions with a health care provider. All decisions regarding patient care should be made with a health care provider. PP-ONC-USA-0605

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