Does Sugar Cause Cancer?

August 18, 2020

Key Takeaways:

  • To date, there are no randomized controlled trial results that show sugar causes cancer.
  • There is an indirect link between sugar and cancer. Eating a lot of high sugar foods can contribute to excess caloric intake, which may lead to weight gain and excess body fat.
  • Being overweight or obese increases the risk of some types of cancer.
  • There are steps you can take to support your overall health, promote blood glucose control, and maintain a healthy weight.

By Mae Reilly, MS, RD, LDN, senior clinical nutritionist at Dana-Farber Cancer Institute

“Does sugar feed cancer?” is one of the most frequently asked questions we receive as oncology dietitians. Researchers continue to investigate the relationship between sugar intake and cancer; meanwhile, there are steps you can take to avoid any potential harm that sugar can cause.

Understanding glucose

Sugar comes in many different forms, but the simplest form is a single molecule called glucose. Glucose is the most abundant monosaccharide (a subcategory of carbohydrates) and all cells, including cancer cells, use glucose as their primary source of fuel.

Glucose comes from any food that contains carbohydrates, including healthful foods like vegetables, fruits, whole grains and dairy. Glucose is also found in refined carbohydrates and added sugars like white breads, pasta, sweets, and sweetened beverages.

What is the link between sugar and cancer?

To date, there are no randomized controlled trials showing sugar causes cancer. There is, however, an indirect link between sugar and cancer.

Eating a lot of high sugar foods such as cakes, cookies, and sweetened beverages can contribute to excess caloric intake. This may lead to weight gain and excess body fat. Studies conducted by the American Institute of Cancer Research (AICR) has shown that being overweight or obese increases the risk of 12 types of cancers, including colorectal, postmenopausal breast, ovarian, and pancreatic cancer.

The good news is that there are steps you can take to reduce your risk. While it is not necessary to completely avoid sugar, reducing added sugars and consuming nutrient-dense, high fiber carbohydrates may be ways to support your health.

Here are some steps you can take to help support your overall health, promote blood glucose control, and maintain a healthy weight:

  • Choose whole grains like whole wheat bread, pasta, brown rice, or quinoa over refined grains like white bread, pasta, and rice.
  • Limit added sugars. The American Heart Association recommends women should have no more than six teaspoons of sugar per day (25 grams) and men should have no more than nine teaspoons of sugar per day (37 grams).
  • Balance your plate. Make 50 percent of your plate high fiber vegetables and fruit. Twenty-five percent of your plate should be protein-rich foods and the other 25 percent should be whole grain carbohydrates or starchy vegetables such as peas, corn, or potatoes.
  • Include a lean protein source with each meal and snack, like skinless poultry, fish, eggs, low fat dairy, tofu, beans, nuts or seeds.
  • Consume a diet rich in vegetables and fruit which contain fiber, vitamins, minerals and immune supporting phytonutrients. Choose whole fruit over fruit juices and dried fruit.
  • Stay well hydrated. Limit sugary beverages such as juice and soda.

Remember: you don’t need to avoid carbs completely.

The idea that sugar could fuel the growth of cancer cells can lead some people to unnecessarily avoid all carbohydrate containing foods. This approach assumes that if cancer cells need glucose, then cutting it out of one’s diet will stop cancer from growing.

It’s not that simple, however: All of our cells need glucose to function, and there is no way for our bodies to supply our healthy cells with the glucose they need while withholding it from the cancer cells. Without adequate carbohydrate intake from foods we eat, our bodies will make glucose from other sources, including protein and fat. This is because glucose is THAT critical for our cells to survive and function properly.

Not consuming sufficient carbohydrates can lead to the breakdown of protein stores in our body, which can contribute to muscle loss and even possibly malnutrition. Following a restricted diet with very low amounts of carbohydrates can also cause unintentional weight loss, which can impact the body’s ability to tolerate cancer treatments.

Restricting carbohydrates also eliminates foods that are good sources of fiber, vitamins, minerals and immune supporting phytonutrients — natural compounds in plant foods (i.e., vegetables, fruits, and wholegrains) that promote overall health.

Remember to bring questions to a licensed professional

If you have nutrition questions, make sure to discuss them with a licensed clinical nutritionist or dietitian. They will be able to work with you and help create an individualized plan tailored to your nutrition goals during cancer treatment and survivorship.