Sugar and Cancer: Is There A Link?

Sugar is the modern-day diet villain, but where does the agreement lie between how sugar and cancer are linked? Does it cause cancer? Does sugar feed cancer cells, making them grow more aggressively? And how does the sugar we consume through food and drink affect our health, and what can be done about this? In this article, we take a long hard look at sugar and its relationship with cancer, busting some myths and covering what researchers are studying in the hopes of finding new ways to treat people with cancer.

  1. Does sugar cause cancer?

Sugar feeds every cell in your body. But does sugar cause cancer, or help it to grow and spread? Our expert says to watch out for added sugars, but not for the reasons you may think.

Does sugar feed cancer cells?

It’s true that sugar feeds every cell in our body — even cancer cells. But, research shows that eating sugar doesn’t necessarily lead to cancer. It’s what sugar does to your waistline that can lead to cancer.

Taking in too many sugar calories may result in weight gain. And, being overweight or obese puts you at a higher risk for cancer and other diseases.

  1. What do our bodies need sugar for and where it comes from in our diet?

Glucose  the fuel of life

When you search for sugar and cancer on the internet, you will find many warnings that sugar is the “white death” that feeds cancer cells.

The idea that sugar is responsible for kick-starting or fuelling cancer’s growth is an over-simplification of some very complicated biology.

-What is sugar?

Sugar is the generic name for sweet-tasting, soluble carbohydrates, many of which are used in food. Simple sugars include glucose (also known as dextrose), fructose, and galactose. Compound sugars or double sugars are molecules composed of two joined simple sugars. Common examples are sucrose, lactose, and maltose. “Table sugar” or “granulated sugar” refers to sucrose, a disaccharide composed of glucose and fructose. Table sugar is extracted from sugarcane or beet. In the body, sucrose is hydrolyzed into fructose and glucose.

Glucose is the basic fuel that powers every single one of our cells. If we eat or drink things that are high in glucose, such as fizzy drinks, the glucose gets absorbed straight into our blood ready for our cells to use..

It’s here that sugar and cancer start to collide because cancer is a disease of cells.

  1. Sugar and cancer?

Cancer cells usually grow very rapidly, multiplying at a high rate, which takes a lot of energy. This means they need lots of glucose. Cancer cells also need lots of other nutrients too, such as amino acids and fats; it’s not just sugar they crave.

Here’s where the concept that sugar fuels cancer was born: if cancer cells need lots of glucose, then cutting sugar out of our diet must help stop cancer growth, and could even stop it developing in the first place. Unfortunately, all our healthy cells need glucose too, and there’s no way of telling our bodies to let healthy cells have the glucose they need, but not give it to cancer cells.

There’s no evidence that following a “sugar-free” diet lowers the risk of getting cancer or boosts the chances of surviving if you are diagnosed. 

  1. What then?

Although there’s no evidence that cutting carbohydrates from our diet will help treat cancer, important research has shown that understanding the abnormal ways that cancer cells make energy could lead to new treatments.

A scientist called Otto Warburg in the ’50s noticed that cancer cells use a different chemical process from normal cells to turn glucose into energy. While healthy cells use a series of chemical reactions in small cellular ‘batteries’ called mitochondria, cancer cells bypass their ‘batteries’ to generate energy more rapidly to meet demand. This discovery was named the Warburg Effect.

This shortcut for making energy might be a weakness for some cancers that gives researchers an advantage for developing new treatments because:

  • First, it opens up the potential for developing drugs that shut down cancer cells’ energy-making processes but don’t stop healthy cells from making energy. And researchers are testing drugs that work in this way.
  • Second, the abnormal processes in cancer cells can also leave them less able to adapt when faced with a lack of other nutrients, like amino acids. These potential vulnerabilities could lead to treatments too.

As these approaches are still experimental, we don’t know yet if treatments that starve cancer cells are safe or if they work.

  1. Why worry about sugar then?

If cutting out sugar doesn’t help treat cancer, why then do we encourage people to cut down on sugary foods in our diet advice?

There is an indirect link between cancer risk and sugar. Eating lots of sugar over time can cause you to gain weight, and robust scientific evidence shows that being overweight or obese increases the risk of 13 different types of cancer. In fact, obesity is the single biggest preventable cause of cancer after smoking, which we’ve written about many times before.

And a study published in 2019 suggested there could be something else going on. Researchers found that people who drank more sugary drinks had a slightly increased risk of cancer, regardless of body weight. The study took weight into account, but there are still lots of answered questions. More studies will be needed to investigate this.

  1. So, should you avoid sugar? Our expert says no.

“Your body’s cells use sugar to keep your vital organs functioning,” says Erma Levy, a research dietitian in Behavioral Science. “But too much daily sugar can cause weight gain. And, unhealthy weight gain and a lack of exercise can increase your cancer risks.”

Eat the right amount of sugar: So, how much sugar is safe to eat?  Women should have no more than six teaspoons per day (25 grams), and men should have no more than nine teaspoons per day (36 grams), says the American Heart Association. This equals about 100 calories for women and 150 for men.

Spot hidden sugar in food: The biggest source of added sugar in the American diet is sugar-sweetened beverages. Other sources include cakes, cookies, pies, and ice cream. Pasta sauce, salad dressings, and canned vegetables also have hidden sugars.

It is very important to read food labels and look for hidden sugars.

Your first clue that a product is high in sugar is if the word “sugar” is listed as the first ingredient.

Some sugary foods don’t include “sugar” on the ingredient list. That’s because sugar is often disguised under different names. Here are some hidden “sugar” words to look out for:

  • fructose (sugar from fruits)
  • lactose (sugar from milk)
  • sucrose (made from fructose and glucose)
  • maltose (sugar made from grain)
  • glucose (simple sugar,)
  • dextrose (form of glucose)

Opt for natural sugars: Natural sugars, like molasses, agave nectar, honey, and maple syrup, are packed with antioxidants that protect your body from cancer.

Avoid artificial sweeteners: Do you prefer artificial sweeteners over sugar?

Some studies done with laboratory animals have found links between artificial sweeteners and cancer. But, no proof exists that says artificial sweeteners definitely cause cancer.

Rein in your sweet tooth: Bottom line: sugar, when eaten in small amounts, can fit into a balanced diet.

  1. So, what is the future for sugar where cancer is concerned?

On the one hand, sugar itself doesn’t cause cancer, and there’s no way (at the moment) of specifically starving cancer cells of glucose without harming healthy cells too. There’s also no evidence that adopting a diet very low in carbohydrates will lower your cancer risk or help as a treatment. And for patients, getting adequate nutrition is important for helping their bodies cope with treatment.

However, it is alarming, the amount of added sugar people are consuming because it’s promoting weight gain. Being overweight or obese increases the risk of at least 13 types of cancer. Although throwing out sugar won’t stop cancer in its tracks, we can all reduce our risk of getting cancer by making healthy choices, and lowering the amount of added sugar in our diets is a good way to help maintain healthy body weight.

  • References:

  1. MD Anderson Cancer Centre (2019): Does sugar cause cancer? Retrieved from
  1. Web MD: Cancer and Sugar: Is There a Link? Retrieved from
  1. Cancer Research UK (2017): Sugar and cancer – what you need to know. Retrieved from
  1. Wikipedia : Retrieved from

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