What’s the Link Between Sugar and Cancer?

If you have cancer, you don’t need to remove all sugar from your diet. Sugar isn’t a direct cause of cancer, and removing it from your diet won’t cure cancer or stop cancer cell growth. No single food can prevent, cure, or treat cancer. 

Does sugar feed cancer?

It’s a myth that sugar feeds cancer cells. Sugar doesn’t directly cause cancer cells to grow and multiply. And sugar isn’t classified as a substance that causes cancer. 

So, what’s the connection between sugar and cancer? Eating a lot of added sugars over a long period can impact your hormone levels and increase your body weight. Both of these can raise your risk of developing cancer. 

Excess intake of added sugars (especially in sugar-sweetened drinks) may be linked to an increased risk of weight gain. And higher body weight is linked to an increased risk of certain types of cancers.

Body fat can increase cancer risk due to its effects on hormone levels. More specifically, body fat around your midsection can increase levels of hormones such as estrogen and insulin. Both of these hormones are linked to a higher risk of developing some types of cancer.

Excess body fat is linked to an increased risk of the following types of cancer:

• Breast 

• Colorectal

• Esophageal

• Kidney

• Liver

• Oral

• Ovarian

• Pancreatic

• Prostate

• Stomach

Sugar is a natural and normal part of a balanced diet. But the Dietary Guidelines for Americans (DGA) recommend no more than 12 tsp (48 g) of added sugars per day — for people with or without cancer. There’s no specific guideline for sugar intake and cancer prevention.

Why do people think that sugar feeds cancer cells? 

All body cells use sugar (glucose) for fuel. This fact has led some to mistakenly conclude that sugar makes cancer cells grow quickly. And that cutting out sugar will stop the growth of cancer cells. But research hasn’t shown either to be true.

Glucose is needed by all cells, not just cancer cells. Even the brain uses glucose as its primary source of energy. It’s not possible to restrict glucose from cancer cells without also affecting the supply to healthy cells. 

The growth of all cells — including cancer cells — is fueled by the breakdown of not only sugars but also fats and proteins. In other words, all body cells are nourished by nutrients from food. So, cutting out all food to slow cancer growth isn’t a viable answer. 

To date, there’s no proof that sugar feeds tumor cells any more than it feeds other cells in your body. There’s also no proof that completely cutting out sugar improves your chances of cancer survival. 

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What are the best foods for people with cancer?

The best foods for people with cancer are ones that you enjoy and can tolerate, especially during treatment. This will be different from person to person. 

Proper nutrition can help with recovery after cancer treatments, reduce side effects, and help support immune health. But eating well during treatment isn’t always easy. For some people, cancer treatments like chemotherapy may cause side effects such as:

• Nausea

• Reduced appetite

• Food aversions

• Dry mouth

• Diarrhea 

If you can’t eat a balanced diet during treatment because of low appetite or other side effects, that’s OK. Know that the side effects are temporary. You can resume a more balanced eating pattern when treatment ends or when you start feeling better. 

In the meantime, you can work with an oncology dietitian to help manage these side effects. During treatment, a dietitian will encourage you to choose foods that:

• Add sources of protein to help with healing: This may include animal protein such as chicken, fish, and cheese. It can also include plant-based protein like tofu, beans, and nuts. 

• Are high in calories to prevent weight loss: If you have a low appetite, make every bite count with high-calorie foods such as peanut butter, cheese, and avocado. 

• Provide fluids to prevent dehydration: Soups, smoothies, and meal replacement beverages are good options. 

What are the best foods to eat to prevent cancer from coming back?

The advice for preventing cancer recurrence is to follow a healthy eating pattern, such as the “New American Plate” proposed by the American Institute for Cancer Research. This eating pattern calls for:

• Filling two-thirds or more of your plate with plant-based foods, including vegetables, whole grains, and beans

• Limiting one-third or less of your plate to animal-based proteins, such as chicken, fish, or eggs

This eating pattern also limits sugar-sweetened drinks, ultra-processed foods, and processed meats, including bacon and deli meats.

What foods should people avoid when going through cancer treatment?

Certain foods carry a higher risk of contamination and infection than others. So, it’s important to avoid these foods during cancer treatment. This is particularly important if your immune system is weakened from chemotherapy, or is immunocompromised. 

During treatment, it’s best to avoid:

• Raw fish or shellfish (like sushi and uncooked oysters)

• Raw nuts (roasted nuts are fine) 

• Raw eggs (cooked eggs are fine)

• Unpasteurized dairy foods such as raw milk (pasteurized milk is fine)

• Foods from bulk bins, buffets, or salad bars

• Foods with mold, including blue cheese 

• Anything that’s past the “best-before” date on the package

• Unwashed vegetables or fruits

• Food that hasn’t been properly refrigerated or sat at room temperature for more than 2 hours

It’s also smart to avoid foods that are frequently recalled due to bacteria, including:

• Sprouts

• Enoki mushrooms

• Cantaloupe

People in cancer treatment should also try to avoid alcohol. Alcohol can interfere with medications and worsen some side effects.

As mentioned above, it’s best to limit added sugars to no more than 12 tsp (48 g) of added sugars per day. This is about 200 calories from sugar. Unfortunately, most people in the U.S. get approximately 350 calories per day from sugar (about 21 tsp). 

It’s important to know that the natural sugar in foods — like fruit — isn’t part of the 12-tsp limit. The limit applies only to “added” or “free” sugars, such as:

• Actual sugars (like white, brown, icing, turbinado, and caster) 

• Syrups (like maple, high-fructose corn, and agave) 

• Ingredients ending in “-ose” (like maltose, glucose, and sucrose)

• Honey

• Molasses

• Fruit juice 

A nutrition facts label will list both total sugars and added sugars. The total sugars listed includes the sugars that are naturally present in a food (like fruit) and added sugars. 

Added sugars are the sugars that are added to foods. The added sugars listed above are what you should pay attention to when reading a food label to understand its sugar content.

How to reduce sugar intake

You can reduce sugar intake by cutting back on sweet foods and drinks, such as soda, candy, and baked goods. These contain high amounts of added sugars. The leading source of dietary sugars for people in the U.S. is sweetened beverages, such as soda and fruity drinks. 

Reducing your sugar intake is easier if you find substitutions for sweet foods so you don’t feel deprived. For example, try eating fruit such as strawberries or frozen grapes instead of candy. Swap soda for carbonated water infused with a squeeze of citrus, fresh mint, or cubed pineapple. 

When you crave a sweet treat, it’s normal and healthy to enjoy them in moderation. The key is to be mindful of your portion size. 

What about added sugars in meal replacement beverages? 

Your care team may suggest meal replacement beverages during cancer treatment. These drinks contain protein, vitamins, and minerals to nourish your body. You may be concerned that these drinks also contain sugar. So, it’s likely confusing if you’re advised to cut out soda, but to drink meal replacements. But consider this comparison:

• A ready-to-use meal replacement drink contains about 14 g (2.5 tsp) of sugar but it also has 27 vitamins and minerals and 10 g of protein. 

• A can of soda contains 40 g (10 tsp) of sugar, with no vitamins, minerals, or protein. 

Think of meal replacement drinks as “mini meals” for when your appetite is low. The small amount of sugar in these drinks isn’t a concern if they help nourish you with essential vitamins and protein during treatment. 

Why trust our experts?

Written by:

Cara Rosenbloom, RD

Cara Rosenbloom, RD, has been a registered dietitian for 22 years. She began her career working as a dietitian at Toronto's Hospital for Sick Children (SickKids).

Edited by:

Meredith Hoffa

Meredith Hoffa is a senior health editor at GoodRx, where she leads journalists and clinicians covering various well-being topics, particularly in diet and nutrition.

Reviewed by:

Katie E. Golden, MD

Katie E. Golden, MD, is a board-certified emergency medicine physician and a medical editor at GoodRx.

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