Is There a Link Between Sugar and Cancer?

There’s some not-so-sweet news when it comes to sugar: Eat too much of the stuff and it can wreak havoc on your health. According to the Centers for Disease Control and Prevention (CDC), consuming too many added sugars — which you’ll find in many packaged and processed foods and drinks — can lead to obesity, heart disease and type 2 diabetes.

But what about cancer? Here’s what researchers know so far about sugar and cancer risk.

Older adults are overconsuming sugar

First, it’s important to know how much sugar is too much. The Dietary Guidelines for Americans from the U.S. Department of Health and Human Services recommends consuming no more than 10 percent of your daily calories from added sugars. If you’re eating 2,000 calories a day, that’s 200 calories, or 50 grams of added sugar. But many adults are not following this advice.

5 top sources of added sugars

The top sources of added sugar, according to the CDC, include:

• Sugar-sweetened beverages (soft drinks, energy drinks, sports drinks)

• Desserts and sweet snacks

• Sweetened tea and coffee

• Candy

• Breakfast cereals and bars

According to a study published in 2023, nearly 30 percent of U.S. adults ages 51 to 70 were considered to be high consumers of added sugars, meaning they consumed 1.5 times the national recommendation. Twenty-two percent of people older than 70 were in this category.

Note that added sugar is not the same as sugar that occurs naturally in fruits, vegetables, legumes and whole grains. “Sugar is in most of the food we eat,” says oncology dietitian Renee Stubbins, assistant professor of nutritional sciences in medicine at Houston Methodist. It provides energy that our cells need to survive.  

The difference is that foods that contain natural sugar, like strawberries and broccoli, also tend to have other essential nutrients, like fiber, antioxidants, vitamins and minerals. “These are cancer-fighting foods,” Stubbins says. Cookies and cupcakes, on the other hand, don’t come with any added nutritional benefits.

Does added sugar cause cancer?

The answer isn’t completely straightforward. Natalie Ledesma, an oncology dietitian with UCSF Helen Diller Family Comprehensive Cancer Center in San Francisco, says we lack studies that identify sugar as a direct cause of cancer. “However, there are trials that show a higher consumption of added sugar is associated with an increased risk of certain cancers,” she says.

For example, in a study analyzing the dietary records of more than 101,000 adults, consuming sugary drinks was associated with an 18 percent higher risk of overall cancer and a 22 percent higher risk for breast cancer. That research was published in the medical journal BMJ. And a review in Cancer Treatment and Research Communications concluded that high sugar intake may elevate cancer risk through insulin resistance and chronic inflammation, both of which can be drivers of cancer.

Sugar can also lead to weight gain, and the CDC says being overweight or having obesity can increase your risk for 13 types of cancer.  

“We definitely know that metabolic dysfunction, which can be driven by having higher blood sugar levels and obesity, increases the risk for developing several different cancer types,” Ledesma says.

In a PLOS One study, metabolic syndrome — a cluster of conditions including abdominal obesity, high blood pressure, high sugar levels, high blood triglycerides and low “good” HDL cholesterol — was associated with an increased risk of 11 cancers, including:

• Colorectal

• Liver

• Pancreatic

• Postmenopausal breast

• Endometrial

• Bladder

• Kidney

• Non-Hodgkin’s lymphoma

• Leukemia

• Lung

• Thyroid

Researchers point to inflammation as one possible explanation. Having more adiposity — or body fat, especially abdominal fat — creates more of an inflammatory state, explains Stubbins, and chronic inflammation can contribute to the development of cancer.  

Keep in mind that you can have metabolic dysfunction even if you’re at a healthy weight.

“Some people can eat whatever they want and never gain a pound, but that doesn’t mean that they’re healthy,” says Kim Geiringer, an oncology dietitian at the Maroone Cancer Center at Cleveland Clinic Weston Hospital in Weston, Florida. “They can have high levels of fat cells in their body, or high cholesterol or triglycerides. They may even have prediabetes or [be] eking towards it, which also puts you at a higher risk of cancer.”

This means that no matter your weight, it’s important to know your metabolic health numbers (blood pressure, cholesterol, blood sugar) and consume a balanced diet, which includes moderating your sugar intake.

What if you already have cancer? The idea that sugar “feeds” existing cancer cells is a common refrain, giving way to the notion that you can starve cancer cells if you don’t give them sugar. But there’s a lot of nuance to this, Geiringer says. 

As the fuel for every cell in our body, glucose (sugar) does feed cancer cells. But our bodies run on glucose, and “unfortunately, you can’t give glucose to healthy cells and not cancer cells,” Geiringer says. “You can’t starve cancer. In fact, when you have cancer, you have increased nutritional needs. You need more calories and protein, so cutting out any food can lead to weight loss and malnutrition, which leads to poor outcomes in cancer,” Geiringer says. One reason: The body requires more nutrients to heal, cope with side effects and keep up energy after what can be very taxing treatments.

In this instance, a dietitian may recommend drinking a milkshake, if that’s what you can stomach, because the sugar risk pales in comparison with the risk of not meeting your calorie needs. Of course, this is based on you as an individual, but it also helps to know that sugar intake was not found to be associated with cancer mortality, according to research published in Nutrition.

Striking the right balance with sugar

All this is not to say you can’t indulge in sweets that can spark a smile or turn a get-together into a celebration. But there has to be a balance, Stubbins says. “It’s important to have functional sugar — found in whole grains, fruits, vegetables — most of the time and occasionally eat the treats,” she adds.

For cancer prevention and overall health, the World Cancer Research Fund says that 40 percent of cancers can be prevented with healthy lifestyle habits. While cutting back on added sugar is one step, it’s not the only one. A cancer-preventive lifestyle includes limiting alcohol, exercising, limiting fast foods, and eating more whole grains, vegetables, fruit and beans.

What about artificial sweeteners?

Some people turn to artificial sugars to get that sweet taste without calories, but there has been concern that they can cause cancer, too. However, according to groups like the National Cancer Institute and the American Cancer Society, nonnutritive sweeteners, or sugar substitutes, have not been found to cause cancer in the amounts we typically consume, though research is ongoing. 

Still, these are often found in ultra-processed foods, which registered dietitians generally advise limiting as well.

Still, there is only so much that’s under your control when it comes to your future health. “Having a healthier diet means there is less of a chance to develop cancer cells,” Geiringer says. “But unfortunately, if you have a genetic predisposition to cancer, diet can help but it may not be completely preventative.”