Cancer and Sugar: Is There a Link?

Medically Reviewed by Laura J. Martin, MD on July 10, 2023
3 min read

You might have heard that sugar causes cancer or makes it grow faster. In some ways, this may make sense. But the science on this isn't clear. It may not be that sugar directly causes cancer.

Every cell in your body uses blood sugar (glucose) for energy. But cancer cells use about 200 times more than normal cells. Tumors that start in the thin, flat (squamous) cells in your lungs need even more glucose to fuel their growth.

The sugar your cells need comes from your diet. It comes in various forms, including: 

  • Fruit (fructose)
  • Vegetables (glucose)
  • Dairy products (lactose)
  • Table sugar and sugar added to drinks or baked goods (sucrose)

Some of those forms of sugar are found naturally in foods, including the fructose in fruit. Others are added sugars, like what’s in a soda, coffee drink, or cookie. Many health organizations, doctors, dietary guidelines, and nutritionists emphasize the need to cut back on added sugars because many people get too much. 

Many experts, including the American Cancer Society and National Cancer Institute, don’t think sugar causes cancer. They say that obesityis the key.

Fat cells release inflammatory proteins called adipokines. They can damage DNA and eventually cause tumors. The more fat cells you have, the more of these proteins you’re likely to have.

Being overweight or obese puts you at risk for at least 13 types of cancer, including breastliver, and colon cancer

But here, too, it’s more complex than just sugar. Obesity is a medical condition that involves many factors.

Other cancer experts say sugar itself can drive cancer. One such researcher is Lewis Cantley, PhD, director of the Meyer Cancer Center at Weill Cornell Medicine in New York.

Cantley thinks some cancers may start with high levels of insulin, the hormone that controls the amount of sugar in your blood. He says his research shows that “having high levels of insulin is likely to drive cancer. And what drives insulin levels is sugar.”

He avoids added sugar himself because he believes the link between sugar and cancer is clear.

Even if you don’t think sugar can cause cancer, it’s wise to limit added sugar. Research says you should get no more than 6 teaspoons a day if you’re a woman and 9 if you’re a man. Yet on average, people in the U.S. get about 17 teaspoons of added sugar each day. That’s around 60 pounds of sugar each year.

Cantley says that means many Americans have high insulin levels all the time and a higher risk of cancer.

Peiying Yang, PhD, a cancer researcher and associate professor at M.D. Anderson Cancer Center in Houston, agrees with cutting back on sugar.

“I would be surprised if reducing sugar consumption wouldn’t help reduce cancer risk,” she says. “It makes sense to limit added sugar, including high-fructose corn syrup in soft drinks, sweetened teas, sports drinks, and processed foods, along with candy, cookies, ice cream, and sweetened breakfast cereal.”

She’s often asked whether it’s OK to eat fruit, since many fruits are high in fructose. Fruit also delivers a wide range of nutrients and fiber. 

“It’s fine to eat fruit as part of a normal diet,” Yang says, “but there should be less fruit than vegetables. If the recommended serving is five fruits and vegetables a day, at least three servings should come from vegetables.” 

It can be tough to track down all the sugar you eat. It’s hidden in things you’d never expect, like soups, salad dressings, peanut butter, yogurt, ketchup, instant oatmeal, nut milks, and hot dogs.

And often, it’s not even called sugar (sucrose) on the label.

There are more than 60 names for added sugar. Some, like maltose, dextrose, and glucose, end in “ose.” Also watch for:

  • Fruit nectar
  • Corn, rice, and maple syrups
  • Honey
  • Molasses
  • Agave

They may sound healthier than sucrose. But to your cells, they’re all just sugar.