The Link Between Sugar and Cancer

Does sugar cause cancer? If you already have cancer, can sugar make it grow faster? It's a loaded question, but the answer is not so simple.

Sugar cubes spilling out of a jar
Lauren Burke / Digital Vision / Getty Images

All of your cells need glucose (blood sugar) for energy. Healthy cells follow a life cycle of growth, division, and death. Like leaves on a tree, old cells die off and are replaced by an equal number of healthy cells. Cancer develops when old cells refuse to die but keep growing, dividing, and building up in one place—creating a tumor.

Does Sugar Cause Cancer?

The idea that sugar causes cancer has been around at least since the 1920s when Dr. Otto Warbug studied the idea. A Nobel Prize-winning cell biologist, he hypothesized that cancer growth was caused when cancer cells converted glucose into energy through glycolysis in the presence of oxygen. The Warburg Effect, present in the majority of cancers, is another name for aerobic glycolysis.

This was an interesting assertion, in part because we know that healthy cells make energy by converting pyruvate and oxygen. The pyruvate is oxidized within a healthy cell's mitochondria. Since cancer cells don't oxidize pyruvate, Warburg thought cancer must be considered a mitochondrial dysfunction.

The current scientific paradigm considers cancer a disease caused by genetic mutations but, this is only partially true as there are cancer cells that lack genetic mutations and they become malignant through epigenetic changes. In general, the metastatic process seems not to be caused by specific genetic mutations and changes in cancer cell metabolism as described by Warburg may play an essential role in metastasis. Many cancers have an avidity for glucose and this characteristic might be explored for therapeutic purposes.

Sugar and Hyperglycemia

Despite finding the flaw in the sugar and cancer theories of the past, there does appear to be some link between excess sugar levels and cancer.

It's well known that people with type II diabetes have an increased risk of several cancers. It's also been shown that an elevated blood sugar level may contribute to the formation of cancer cells (oncogenesis), resistance to cell death in cancer cells (apoptosis resistance) and tumors becoming resistant to chemotherapy.

Whether this is of concern with "normally" elevated blood sugars, such as after a dessert splurge rather than with insulin resistance and elevated blood sugars, isn't entirely certain.

Sugar and Proteins Keep Cancer Cells Alive

It's been said that cancer cells are immortal—they don't die off in an orderly way as healthy cells do. Scientists have studied this effect and may have discovered what tumor cells do to avoid cell death. In laboratory research at Duke University, cancer cells appear to use a combination of sugar and specific proteins to keep growing when they should die. These cancer cells appear to use sugar at a high rate, in order to ignore cellular instructions to die off.

Developing New Sugar-Coated Cancer Drugs

At Johns Hopkins University, a group of researchers looked at ways to fool cancer cells into growing more slowly and then eventually killing themselves. They studied abnormal glycosylation—how cancer cells put sugar and proteins together to sustain themselves.

When these cells were given n-butyrate (a salt) with carbohydrates (complex sugars), their growth slowed. In order to feed the cancer, a death-dealing drug, researchers produced a hybrid molecule made of a simple sugar and n-butyrate. Because the cancer cells absorbed the sugar readily, they soaked up this new molecule, which interfered with their ability to keep growing, and they died.

Other teams of scientists are working on drugs that will take advantage of cancer's weakness for sugar. Some of these new drugs may be given along with chemotherapy, to make tumor cells more sensitive to chemo drugs.

In Switzerland, scientists are using a sugar coating on "quantum dots" or nanocrystals of drugs that would travel to the liver only, avoiding other organs. It's the sugar on those little doses that help the drugs target one particular part of the body, thereby reducing side effects and increasing the effectiveness of the drugs.

Obesity and Cancer

Having a sweet tooth and consuming more sugar based foods is linked to obesity, and obesity is linked to cancer.

Obesity alters hormone levels in the body, which are associated with a greater risk of both developing cancer and having cancer recur or progress.

According to the International Agency for Research on Cancer, one of the best things you can do both to prevent cancer in the first place, and prevent recurrence if you've already been diagnosed, is to be as lean as possible without being underweight.

Be Smart About Sugar in Your Diet

Sugar provides energy but doesn't give you any nutrients that are needed to reduce your cancer risk.

Natural sugars are found in fruits and dairy products and can be part of a healthy diet. Added sugars—the kind that's added to food during processing, such as white sugar, corn syrup, and fruit juice concentrate—should be avoided or limited. Consuming too many sugar calories can lead to obesity and high insulin levels, which would contribute to your increased cancer risk.

Cut back on sugar-loaded foods such as candy, baked goods, sugary cereals, and sodas to reduce your cancer risk. Balance your diet with plant foods, fish, and whole grains—​parts of a healthy diet that have been linked to a lower risk of cancer. 

A Word From Verywell

It's okay to eat some natural sugars on a daily basis, especially when they're part of nutrient-dense foods, such as milk or fruit. Sugar in your diet does not cause cancer to develop. Starving all of your cells of sugar won't kill or prevent cancer. Keeping a balance of nutritious foods and a regular exercise routine can give you a healthy body weight and normal insulin levels. That's the sweet way to reduce your cancer risk.​

4 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Liberti MV, Locasale JW. The Warburg Effect: How Does it Benefit Cancer Cells?. Trends Biochem Sci. 2016;41(3):211-218. doi:10.1016/j.tibs.2015.12.001

  2. Collins KK. The diabetes-cancer link. Diabetes Spectr. 2014;27(4):276-80. doi:10.2337/diaspect.27.4.276

  3. nternational Agency for Research on Cancer. IARC has updated its evaluation of the link between obesity and cancer in volume 16 of the IARC handbooks of cancer prevention.

  4. American Institute for Cancer Research. The sugar and cancer connection.

Additional Reading

By Lynne Eldridge, MD
 Lynne Eldrige, MD, is a lung cancer physician, patient advocate, and award-winning author of "Avoiding Cancer One Day at a Time."