Does sugar feeds the cancer cells?

Jun 24, 2016
Does sugar feeds the cancer cells?

Have you heard suggestions that cancer patients should not take sugar, that sugar feeds cancerous cells, and that abstaining from sugar would help kill these diseased cells? The logic follows that cancer patients should avoid table sugar and sugar-containing food e.g. bread, buns, cakes, pastries, puddings, and jellies.

No, this is just another myth.

Every cell in our body, cancer cells included, depends on glucose for fuel. Glucose is the smaller substrate that derives from sugar-containing food, or “the carbohydrate group”. When we consume food containing carbohydrates, such as starchy vegetables, fruits, rice, grains and dairy products, our body will digest carbohydrates into glucose. Glucose can also be broken down from sucrose (table sugar).

Glucose is the primary substrate for energy production in cells, especially the brain cells. Our body needs energy for physiological functions e.g. to replenish old cells, to transport oxygen and to fight infection.

Glucose can be stored in liver and muscle in the form of glycogen. Glucose can be produced within our body from protein and fat when we run out of stored glycogen. Without glucose, our body will have no energy to carry out daily activities and physiological functions.

Therefore, avoiding sugar will not help you fight cancer. It actually weakens your body. When out of energy, your body will burn use fat and protein for fuel. Subsequently, you will lose weight and your immunity will be slashed.

Don’t even think that you can “selectively” direct sugar to healthy cells and “bypass” cancer cells. It is biologically impossible that our body can pick and choose which cells get what fuel. By abstaining from sugar, the cancer cells will not die. Instead, you will be killing off healthy cells.

Cancer cells may burn sugar at a higher rate than other cells, but at this point it has not been clinically shown that eliminating dietary sources of sugar and carbohydrate can slow tumour growth.

Research does suggest a correlation between sugar and cancer risks, but no direct causation effect is known. The focus is mainly on prevention.

High-sugar diets supply excess calories more than the body needs. Surplus calories will be stored as body fat, which will eventually increase body weight. It is overweight or obesity that is linked to greater risk of some cancers e.g. post-menopausal breast cancer and colorectal cancer.

Therefore, it is sensible to limit sugary food as part of a healthy lifestyle, which could reduce risk exposure to cancer and other diseases e.g. diabetes. Moderation is the key. Dietary balance and regular exercise are necessary components to a healthy lifestyle. Cutting off sugar and carbohydrate all together will do your body no good.

Patients on chemotherapy and radiotherapy are encouraged to have a greater variety of food.

Sugar can be part of your diet. It enhances the taste of food and drinks. You don’t have to avoid sugar. In a case of a low appetite, try adding some sweetness into your diet. You may freely select sugar-containing food such as cakes, muffins, and kuihs.

There is no harm to add some sugar into your drinks too. Sweetness typically boosts appetite. For patients with difficulty swallowing e.g. nasopharyngeal patients, good choices include soft food like jellies, puddings, ice creams and smoothies.

However, too much sugar can easily raise the blood sugar levels of diabetic patients. When treating cancer, your doctor will help you control the blood sugar level. Don’t forget to take diabetic medication as per usual routine, and your dietitian will be able to guide you on your diet. If you are non-diabetic, there is nothing to worry about sugar intake during cancer treatment.

To conclude, avoiding sugar when you are on cancer treatment is definitely a wrong idea. Your body needs the energy to see you through the treatment. Bear in mind that carbohydrates and sugar are only part of your diet. Do not forget the other nutrients, like protein, to ensure a balanced meal and to help the body heal some side effects from cancer therapy.

You can always seek your dietitian’s advice if ever you feel unsure about your diet.

By Mount Miriam Cancer Hospital's Dietitian, Marcus Lee.


To read or find out more about cancer, treatments, consultant articles and dietary articles, check out our new Cancer Resource & Information Centre at

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