Our diet plays a big role in our overall health. We know eating plenty of fruits, vegetables, and whole grains is good for us, while eating too many sugary foods is not. But does sugar have the ability to cause cancer?
The bottom line is that eating sugar in moderation as part of a healthy diet does not cause cancer. However, eating excessive sugar can contribute to an unhealthy dietary pattern or obesity, which is a risk factor for cancer. Here, learn where the idea that sugar can cause cancer came from, what the science currently says about sugar and cancer risk, and what to know about eating sugar in moderation.
Where did the idea that sugar causes cancer come from?
When we eat food containing carbohydrates, including foods that contain sugar, our body breaks it down into glucose. That glucose then fuels our cells to make the energy we need to survive. This process is called metabolism.
Normal cells and cancer cells both use glucose for energy. Scientists know that cancer cells metabolize glucose faster than normal cells. It’s part of something called the Warburg Effect, named after the German scientist Otto Warburg, who studied cancer in the early 20th century.
The Warburg Effect even has a practical application in diagnosing cancer. In an imaging test called a positron emission tomography (PET) scan, doctors inject radioactive glucose into the bloodstream. Since cancer cells metabolize glucose at a faster rate, the PET scan lights up the location of cancer cells and tumors in your body. Doctors can use the image to find cancer or evaluate how well cancer treatments are working.
Today, some scientists are working on treatments to destroy cancer cells by starving them of glucose. They hope to alter genes that affect the cancer cells’ metabolism or develop drugs that would target cancer cells’ metabolism.
Can eating sugar cause cancer?
You might be wondering whether the sugar in the foods you eat can cause cancer cells to develop. The short answer is no. No studies in people have shown that reducing sugar intake prevents or treats cancer. Furthermore, no studies have shown that eating too much sugar causes cancer. In other words, there is not a direct link between sugar and cancer.
Some research in this field includes studies of soft drinks, which have high amounts of sugar. A 2006 study in the Journal of the National Cancer Institute by Yale researchers, for example, found no connection between soft drink consumption and an increased risk for esophageal cancer. Meanwhile, a 2019 study in PLOS One found no link between soft drink consumption and colorectal cancer, and a 2012 study by researchers at the National Cancer Institute found no association between dietary sugars and an increased risk of colorectal cancer or any other major cancer.
What about sugar, obesity, and cancer risk?
A growing body of research shows that eating too much sugar may affect body weight. It may contribute to obesity, which is having a body mass index (BMI) of 30 or higher. This in turn can increase your risk for cancer and other diseases. The World Cancer Research Fund and the American Institute for Cancer Research (AICR) say that being overweight or obese throughout adulthood is associated with an increased risk of 12 different cancers. Researchers are still investigating the link between obesity and cancer. There are many factors that could play roles in how obesity impacts cancer risk, including hormones, inflammation, or how weight bias factors into medical care.
When thinking about methods of cancer prevention, maintaining a healthy body weight is important. You can maintain a healthy body weight by exercising regularly, eating nutritious foods in appropriate portions, and paying attention to hunger or fullness cues.
"Most people know that consuming an excess amount of simple sugars is not good for them. But having some sugar, some of the time, is a perfectly normal and healthy way to eat. What would our quality of life be like if we never have the birthday cake, or the brownie, or the fancy punch at the family reunion? I encourage my clients to find a balance that works for them." – Julie LG Lanford, MPH, RD, CSO, LDN, registered dietitian and nutritionist with 15 years of experience working in oncology nutrition
What is considered a healthy sugar intake?
Sugar is found naturally in fruits, vegetables, whole grains, and milk. These products also contain different nutrients, vitamins, and minerals, so they are generally considered as the best nutritious sources for your body’s energy needs.
Companies also add sugars to processed food and drink products they make to improve their taste or to increase the shelf life of the product. These are called “added sugars.” Registered dietitians and other health care professionals generally advise limiting added sugars in order to promote good health.
Sweetened beverages like soda are the leading source of added sugar in the United States, with desserts and sweet snacks close behind, according to “Dietary Guidelines for Americans, 2020-2025,” published by the U.S. Department of Agriculture and the U.S. Department of Health and Human Services. The same guidelines recommend consuming less than 10% of your daily calories from added sugars and avoiding food and drinks with added sugars. The American Heart Association recommends that women consume no more than 25 grams (100 calories or 6 teaspoons) per day and men no more than 36 grams (150 calories or 9 teaspoons) per day from added sugars. These guidelines apply to all people, regardless of whether or not they have cancer. Currently, it is estimated that people in the United States consume an average of 77 grams of added sugars per day.
When buying food, be sure to look at the Nutrition Facts label, which lists both the total sugars and added sugars per serving. Try to eat a variety of foods, including vegetables, fruits, and whole grains.