Debunking nutrition myths

Today, lets talk about the statement “sugar feeds cancer”

I see so many posts on social media claiming that “sugar feeds cancer” and that cancer sufferers should avoid all sugar to avoid feeding their tumour(s). I have also heard of people claiming to be nutrition “experts” advising others that this is the case. But is there any truth in this statement and what is the whole story?

First we need to look at the science.

Many people skip breakfast, often citing lack of time as the main reason. However, eating a healthy breakfast has been shown to have a wide range of health benefits. Here are 5 excellent reasons to have a healthy breakfast:

The “sugar” being referred to is glucose and the main source of glucose is carbohydrates. Carbohydrates are in foods such as bread, potatoes, pasta, breakfast cereals and fruit. As soon as you start eating these foods, your body release enzymes in the mouth to start breaking down the foods and then again in your intestines to break it down further into sugars. These are then converted to glucose (the simplest form) which is absorbed into the small intestine and passes into your blood stream, causing your blood glucose levels to rise. In response your pancreas releases insulin and this acts as a key to unlock your cells and allows the glucose to enter them, thereby regulating your blood glucose levels. All of your cells need glucose to function, as well as amino acids (the building blocks of protein), and fats. Your brain, especially, requires glucose and without it your brain will not be able to function efficiently. After your body has used the glucose it needs, the leftovers are stored as glycogen in the liver and muscles to be used when it’s needed and your body can store enough of this fuel to last you about one day.

So we have established that your cells in your body need glucose to function. Now what about cancer?

Cancer occurs when cells mutate during cell growth and division. Therefore cancers are cells. This has led people to claim that as cancers are formed from mutated cells, then surely glucose must feed cancer. End of story.

The undeniable answer is that glucose feeds every cell in the body, including cancer cells. However, it is important to realise that if you cut out glucose from your diet, you are also causing every other cell in your body to be denied glucose, including your brain. Your body needs glucose. It wants glucose. So if you take this energy source away from it, it will look for alternative sources of glucose, and it will do this by breaking down your fat stores and then the protein in your muscles to release the glucose. So now your body still has a source of glucose, however it is now in a catabolic state, meaning that you are losing muscle in order for your body to maintain an adequate glucose supply.

This is dangerous for those already suffering with a disease which already exerts a catabolic effect on the body. One of the most important factors in aiding recovery, or being strong enough to endure medical treatment, or to improve the quality of your life is to have good nutrition and by eliminating glucose from your diet, you are not only cutting out major sources of energy and nutrition but you are also risking your muscles being broken down​which will result in undesired weight loss and fatigue. Weight loss can impact medical treatment so it is vital to ensure that you are getting the right nutrition.

Another important point is that a cancer diagnosis is hugely stressful. You are trying to cope with the diagnosis itself, the impact on your life and that of your family, medical treatment and its side effects, as well as the side effects of the cancer itself. The idea then that “all sugars” directly fuels the growth of cancer cells may lead you to want to eliminate them completely from your diet and this will just add more stress into the equation.

Stress will trigger your fight or flight response, which in turn increases the hormones that can raise your blood glucose levels and suppress your immune system. Rather than adding to your stress levels, trying to find ways to reduce them through meditation, yoga, or a favourite hobby will not only have a positive physiological impact but also positively impact your mental health.

It is inevitable that some people will decide to eliminate the majority of carbohydrates and follow what is called a ketogenic diet but this needs careful supervision as it is very high in fat and very low in carbohydrates and protein and can lead to unintentional weight loss. Diets high in saturated fat can also increase your risk of a number of health concerns, including cardiovascular disease.

There is ongoing research into low carbohydrate diets and cancer but currently there is no evidence that these diets are beneficial for most people with cancer; in fact, some research has shown that a low fat diet, which is the opposite to the high fat content of the low carbohydrate diet, may improve survival after diagnosis for some cancers.

The key message I am putting across here is please do not listen to non-evidence based, dangerous messages on social media by those who do not have a science background and who do not understand the anatomy and physiology of the human body. Always contact a registered dietitian if you are concerned about your weight or other nutritional elements of your diet for evidence-based, practical advice and support.