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Body Soul Nutrition | Is it really true that sugar feeds cancer?
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Is it really true that sugar feeds cancer?

Is it really true that sugar feeds cancer?

This is a modified version of an original article written by Liz Butler that featured on

The idea that a healthy diet is supportive for people living with cancer is nothing new in the world of natural medicine and it’s great to see this idea starting to penetrate mainstream medicine (yes I know there’s still a long way to go). The growing acceptance amongst conventional medical professionals of the importance of nutrition in cancer has been fuelled by some very positive research studies in recent years but there’s one idea that’s still guaranteed to raise an eyebrow and a look of scepticism from your doctor which is the suggestion that dietary sugars feed cancer. It might sound crazy to your doctor, and perhaps to you, but if you dig a little deeper you’ll find that this idea has some serious scientific grounding.

Otto Warburg is one of the most highly regarded medical scientists that ever lived, having been nominated for the Nobel prize an unprecedented 3 times for 3 separate achievements. Over 90 years ago he made the discovery that cancer cells produce energy in a slightly different way to healthy cells – without using oxygen (anaerobic respiration) instead of the normal process that uses oxygen (aerobic respiration). Both types of respiration require glucose as the raw material but anaerobic respiration, being a less efficient process, requires more glucose to produce each unit of energy. The upshot is that cancer cells require more glucose than normal cells to create the energy they need to survive.


The fact that cancer cells require more glucose has been verified many times since the initial discovery was made and is now well-established in medicine. In fact doctors use a diagnostic tool known as Positron Emission Tomography (or PET scans) that make use of this knowledge – radioactive glucose is injected into the patient and then traced on scanning equipment to where it’s being most rapidly used up, in this way it identifies the exact site of the tumour and how active it is.

Warburg’s findings form the grounding for the idea that sugar feeds cancer and many people have taken the leap from his work and arrived at the conclusion that because cancer cells are particularly ‘glucose hungry’ this must mean that if we eat sugar we will fuel cancer cell growth. This is an obvious assumption but is it really true?

At this stage it is impossible to give a definitive answer as to whether or not chronically high blood glucose levels directly encourage cancer growth, but early research seems to suggest that there is certainly some sort of an association. For example, a number of studies have looked at whether a diet that is high in sugar, or one that promotes high blood glucose levels, increases the risk of developing cancer. Many of these studies, although not all, have shown that yes, these diets do increase the risk. Also several studies have assessed people living with cancer and shown that a wholefood diet (one that happens to be low in sugar) is supportive for health and in some cases may slow cancer progression. Finally, there is work underway looking at ketogenic diets, which are very low in carbohydrates and initial results show benefits for those with brain tumours.

The link between sugar and cancer is not limited to the direct feeding of cancer cells as there are other ways in which this compound will undermine the health of those with this disease. These include the fact that high levels of glucose in the blood lead to high insulin levels, a hormone that encourages proliferation and growth of cancer cells. Also sugars encourage weight gain and obesity is known to promote cancer progression. Finally, a high sugar diet appears to interfere with normal immune function promoting chronic inflammation. This type of inflammation has been strongly linked with the initiation and further development of cancer.

Putting all of this information together it becomes clear that sugar has great potential to undermine the health of someone with cancer and for this reason at Body Soul Nutrition we believe a low-sugar diet is essential for someone with cancer. Our advice to clients extends beyond sugar itself as it’s important to understand that starch, found in grains and starchy vegetables such as potatoes will also raise glucose levels in the blood. Commonly we are asked whether honey and syrups count as sugar and the answer here is ‘yes’. We are also asked about fruit and whether or not this should be excluded. Fruit is packed full of phytonutrients with powerful health-enhancing properties and although it contains some sugar, the sugar comes packaged with fibre and nutrients that help to regulate blood glucose. Therefore the advice we give is to continue to include fruit in the diet but to stick mainly to those that grow in temperate climates as these tend to be less sweet. If you are considering quitting  sugar but are concerned that it will be too difficult, rest assured; following a low-sugar diet is easier than it sounds as the desire for sugar drops significantly when you stop eating it, and as the benefits of this diet are usually felt very quickly the motivation to carry on avoiding sugar is strong.

The current line from big cancer organisations such as Cancer Research UK is that sugar does not feed cancer but while there’s not yet conclusive proof that dietary sugars directly fuel cancer growth, it is becoming increasingly clear that a high sugar diet will shift the body’s biochemistry towards a state that is more favourable for cancer growth. As awareness of the negative impact of sugar on general health grows it is my hope that before long the potential benefits of a low-sugar diet for those with cancer will enter the mind-set of mainstream health professionals. But there’s no reason to wait until that happens to reap the benefits, simple changes are all it takes to shift your body in the direction of health and these are steps you can start taking today!



Liz Butler

Ever since I can remember I’ve been fascinated with how the body works and all things health-related. Running alongside this interest has been my deep need to know what makes us ‘work’ at a level beyond the physical body. What stimulates our desires, what motivates us to grow and develop emotionally, and what touches our soul. I’ve sought answers to these big questions through my own self-discovery and through my work. My interest in health has settled around the subject of nutrition and I’ve spent my career advising people with cancer how to follow a diet and lifestyle that supports physical health and emotional wellbeing.

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