Should I avoid sugar if I have cancer?

All cells need fuel for energy. The primary fuel is a simple sugar, glucose, which is used by our cells to release energy.

In the 1920s, a German scientist called Otto Warburg found that cancer cells use up a lot of glucose. It isn’t clear why cancer cells do this, but it may have advantages in ensuring sufficient building blocks are available for rapidly dividing cells.

More recent research has looked into using diet therapy to ‘starve’ cancer cells of energy. By removing dietary sources of glucose, it has been suggested that cancer cells would not be able to fuel growth and replication, even though the body can make glucose in the absence of any dietary sources of glucose.

Most studies have focused on the ketogenic diet, which restricts the intake of sugar and carbohydrates to very low levels. A 2018 review of all the available studies on the ketogenic diet and people living with cancer found that overall, there was not enough high-quality research. On the basis of this, no-one has yet proved that sugar directly causes cancer.

However, too much sugar can lead to an increase in calories, which can then lead to weight gain. Research shows that being overweight or obese increases the risk of cancer.

If someone living with cancer chose to restrict their intake of all sugars, their intake of fruits and vegetables could be restricted as well, and we know that consuming a variety of fruit and vegetables provides a number of essential vitamins and minerals that can support recovery.

However, for general health, we should try to limit how much added sugar (food and drink that has had sugar added to them) we have, such as full-sugar soft drinks, syrups, cakes, biscuits, chocolate and sweets.

> Does sugar cause cancer growth?

> Find out more about eating well during cancer

Read our cancer prevention recommendations

> Avoid high-calorie foods and drinks

> Limit sugar sweetened drinks


In association with

NIHR cancer and nutrition collaboration logo


British Dietetic Association logo