Sugar and Cancer

Sugar and Cancer: What You Need to Know

What is the relationship between sugar and cancer?

The connection between intake of sugar and cancer risk has been highlighted more frequently in recent years, as the importance of dietary factors are taken more seriously by researchers and governments. But trying to find a clear answer about whether sugar causes cancer is difficult, you can find convincing arguments both for and against the theory. In this article we look at some of the evidence, and discover what reputable cancer centres say on the topic.

Cancer cell metabolism

Normal, non-cancerous cells produce energy via tightly controlled metabolic pathways that regulate the oxidative breakdown of pyruvate. Cancer cells however generate energy from glycolysis (the non-oxidative breakdown of glucose) followed by lactate fermentation (the ‘Warburg effect’).

Rapidly proliferating tumour cells have glycolytic rates of up to 200 time higher than normal, non-cancerous cells. This rate of anaerobic glycolysis occurs even in the presence of oxygen1,2.

It is this basic process of cancer cell metabolism that has led to the assertion that high levels of sugar (glucose and fructose) in the diet can either cause cancer, lead to increased risk of cancer and/or cause cancer cells to grow and spread more rapidly.

It is a fact that refined sugar consumption has risen rapidly in the industrialized world, in parallel with a rapidly rising rate of cancer incidence.

The theories on how sugar and cancer are connected can be broken down into two camps. The direct effect of sugar on cancer cell metabolism, and the indirect effect of sugar on increasing obesity levels (leading to an increased cancer risk).

Direct effect on cancer metabolism

It is often asserted that because cancer cells require glucose to function and grow, cancer patients should reduce the amount of sugar that they eat, thus starving the tumour of food and restricting the ability of the cancer cells to proliferate.

Science clearly supports a link between sugar and cancer cell metabolism
Science clearly supports a link between sugar and cancer cell metabolism

Recent research has suggested a number of ways in which glucose and fructose can directly impact on cancer cells. One study found that increased sugar activates and promotes several pathways that cause cancer3. It has also been shown that starving cancer cells of sugar could be used to treat colorectal cancer4, and that people with elevated glucose have a higher risk of getting cancer5. Scientists have also demonstrated that immature sugar molecules could aid the growth of malignant tumours6,7.

Science clearly supports a link between sugar and cancer cell metabolism. It also supports the notion that sugar aids the metastasis of cancer cells (the ability of the cancer cells to spread to other sites in the body).  

However, the MD Cancer Institute, Mayo Clinic, Cancer Treatment Centers of America and Cancer Research UK all stress that while a healthy diet is vital, reduced dietary sugar levels have not been shown to have a direct effect on tumour progression or cancer cell proliferation.

Indirect effect of sugar on increasing obesity

What these institutes do recognise, is the link between excessive sugar intake and obesity. It is widely accepted that after smoking, obesity is the largest preventable cause of cancer8.

sugar and cancer
Too much added sugar in our diets is a major cause of obesity

Obesity is associated with an increase in risk of cancer of the oesophagus, pancreas, colon, rectum, breast, endometrium, kidney, thyroid and gallbladder9. Too much added sugar in our diets is a major cause of obesity.

So should you cut out sugar?

Julie Baker, Clinical Oncology Dietitian at the Cancer Treatment Centers of America says:  “Our bodies use glucose, the simplest unit of carbohydrate, as their primary fuel. Without adequate carbohydrate intake, our bodies will obtain glucose, or fuel, from another source. Possibilities include the breakdown of proteins we eat or proteins stored in our body, which may ultimately lead to muscle loss and malnutrition”10.

In other words, cutting all sugar from a cancer patient’s diet would cause more harm than good, as the body’s healthy cells would also be unable to function properly.

In summary

Scientific studies show that sugar does directly impact on the metabolism of cancer cells, however there is a lack of scientific evidence to show that cutting all sugar from the diet can prevent cancer from forming, growing or metastasizing. Leading health authorities agree that cutting refined sugar and processed food from your diet is beneficial for everyone and that a healthy diet is an important factor for reducing cancer risk related to obesity.

It is important that if you have cancer, you don’t reduce your natural sugar intake to the point at which the healthy non-cancerous cells in your body will suffer.


You can learn more about the intricate relationship between food and cancer by reading the book ‘Food to Fight Cancer: What Your Doctors Aren’t Ready to Tell You‘. Learn which foods contain compounds that fight cancer, and which foods promote cancerous growth.





About the author: 

Sonia Nicholas is a Biomedical Scientist and Freelance Clinical Science Writer & Editor. She has been working in the field of clinical science for fifteen years.

Sonia believes that everyone can improve their health by eating a clean diet – a claim that scientific research increasingly supports. Sonia also believes that healthy, clean eating is accessible to all and doesn’t have to be an expensive lifestyle choice.

All of the information on The Green Apple Club website is evidence based and fully scientifically referenced.

Leave a Comment

We would love to hear your comments, but please keep them respectful and friendly. Differences of opinion are fine, but we will not tolerate any trolling, abuse or judgment of other people's choices.

Leave a Comment

Your email address will not be published. Required fields are marked *