"Does sugar feed cancer?" is one of the most frequent questions we receive as oncology dietitians. While researchers continue to investigate the relationship between sugar intake and cancer, it remains a source of uncertainty and fear for many cancer patients and their caregivers.
Sugar comes in many different forms, but the simplest form is a single molecule called glucose. All cells, including cancer cells, use glucose as their primary fuel. Glucose comes from any food that contains carbohydrates including healthful foods like vegetables, fruits, whole grains and dairy. Glucose also comes from refined carbohydrates and added sugars like white breads, pasta, sweets and sweetened beverages.
The idea that sugar, or glucose, 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. Unfortunately, it’s not that simple. All of our healthy cells need glucose to function, and there is no way for our bodies to let healthy cells have the glucose they need, but not give it to the cancer cells. Without adequate carbohydrate intake from foods we eat, our bodies will make glucose from other sources, including protein and fat. 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 possibly malnutrition. Following a restricted diet with very low amounts of carbohydrates can also cause unintentional weight loss. This can impact the ability to tolerate cancer treatment. Restricting carbohydrates also eliminates foods that are good sources of fiber, vitamins, minerals and immune supporting phytonutrients.
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. Research has shown that being overweight or obese increases the risk of 11 types of cancers including colorectal, postmenopausal breast, ovarian, and pancreatic cancer.
While it is not necessary to completely avoid sugar, reducing added sugars and consuming nutrient-dense, high fiber carbohydrates may be most effective. 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.