Sugar & Cancer

The myth:

We always hear myths about cancer, one of them is “sugar can feed cancer cells”. To gain credibility, the anonymous author of this statement claimed that it is released by certain research institutions. According to the author, if a cancer patient refrains from eating sugar, the cancer cells will die.

The truth:

There is no scientific evidence to show that cancer cells preferentially feeds on sugar over healthy cells. Every cell in our bodies, including cancer cells, uses sugar (glucose) for fuel.  When we eat food that contains carbohydrates, including starchy vegetables, fruits, rice, grains and dairy products, our bodies will digest the carbohydrates into glucoses. Glucose is the smallest substrate that can be used to produce energy. All cells in our bodies will use the energy from glucose for metabolism i.e. replenish old cells. Glucose can be stored in our liver and muscle in the form of glycogen. Glucose also can be produced within our bodies from protein when we are out of glycogen storage. Without glucose, our bodies would have no energy to move, all physiological systems would unable to function normally, and our brains would eventually shut down.

Therefore, it is impossible to turn our bodies into “zero sugar” in hope of the cancer cells will be died of starvation. In fact, you are starving your whole body, subsequently you will become underweight and with weak immunity. It is also biologically impossible that our bodies can pick and choose which cells get what fuel. Don’t try to think of you can “selectively” send sugar to healthy cells and “bypass” the cancer cells. Human body is a complex structure, every mechanism in the body is linked. If you starve your body, you are actually asking your body to work under constraint.

Cancer cells do have faster metabolism rate, it may “eat” sugar faster than other cells, but at this point, it has not been shown that eliminating dietary sources of sugar and carbohydrate can result in slower growth of cancer cells.

Bottom line:

There is a connection between sugar and cancer risk, but it’s more indirect and mainly focus on prevention. Eating a lot of high sugar foods may supply calories to your body more than you need, excessive calories will be stored as body fat, which eventually leads to increased body weight. It is overweight or obesity that is convincingly linked to greater risk of some cancers, examples are post-menopausal breast cancer and colorectal cancer. Therefore, it is sensible to limit sugary foods as part of an overall healthy diet in order to prevent cancer and other diseases (i.e. diabetes).

However, avoiding sugar when you are treating cancer is definitely a wrong concept. Remember that your body need energy to help you go through the treatment. Keep in mind that carbohydrates and sugar are only part of your diet, it’s also important to look into other nutrients like protein to make sure that what you are eating enough to cover some of the side effects of treatment.


American Institute of Cancer Research.

Marcus Lee, Dietitian