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There’s a lot of confusing information and advice out there around sugar.

It’s been made the villain of our diet, but where does the consensus lie between how sugar and cancer are linked?

Does it cause cancer? Does sugar feed cancer cells, making them grow more aggressively? And how does the sugar we consume through food and drink affect our health, and what can be done about this?

In this post we’re taking a long hard look at sugar.

We’ll focus specifically on sugar and cancer, busting some myths and covering what researchers are studying in the hopes of finding new ways to treat people with cancer.

And we’ll cover why the amount of sugar in our diets is cause for concern. A high-sugar diet can be bad news when it comes to cancer risk, but not for the reasons that often appear in the headlines.

But first the basics, what our bodies need sugar for and where it comes from in our diet.

Glucose – the fuel of life

Search for sugar and cancer on the internet and it doesn’t take long to find alarming warnings that sugar is the “white death” and “cancer’s favourite food”.

But this idea that sugar is responsible for kick-starting or fuelling a cancer’s growth is an over-simplification of some complicated biology. Let’s start with what sugar actually is.

Sugar comes in many different forms. The simplest form is just as a single molecule, such as glucose and fructose. These molecules of simple sugars can also stick together, either in pairs or as longer chains of molecules. All of these combinations of molecules are carbohydrates, and are our body’s main source of energy.

The form of sugar most of us will be familiar with is table sugar, which is a simple sugar that dissolves in water and gives things a sweet taste. Its proper name is sucrose, and it’s made up of crystals of glucose and fructose. Table sugar is refined, meaning it’s been processed to extract it from a natural source (usually sugar beet). Unprocessed foods can be high in simple sugars too, for example honey (also made mostly of glucose and fructose) is nearly pure sugar.

As chains of sugar get longer, they lose their sweet taste and won’t dissolve in water anymore. These chains are called polysaccharides and form a large component of starchy foods. Starchy foods such as rice, bread, pasta and vegetables like potatoes might not taste sweet, but they are high in carbohydrate too.

Sugar, in some form, is in many things we eat. And this is good, because our bodies rely heavily on it to work.

Nearly every single part of our body is made of living cells. And it’s these cells that help us see, breathe, feel, think and much more.

While their jobs in the body may differ, one thing all these cells have in common is that they need energy to survive and perform their duties.

Cells somehow need to turn nutrients in our diet into a form of energy that they can use, called ATP. It would take a long time to explain this (if you’re interested you might want to read more), but simplistically the process starts with glucose.

Glucose is the basic fuel that powers every single one of our cells. If we eat or drink things that are high in glucose, such as fizzy drinks, the glucose gets absorbed straight into our blood ready for our cells to use. If a starchy food, such as pasta, is on the menu, the enzymes in our saliva and digestive juices break it down and convert it into glucose. And if for some reason there’s no carbohydrate in our diet, cells can turn fat and protein into glucose as a last resort, because they need glucose to survive.

It’s here that sugar and cancer start to collide, because cancer is a disease of cells.

Sugar and cancer

Cancer cells usually grow quickly, multiplying at a fast rate, which takes a lot of energy. This means they need lots of glucose. Cancer cells also need lots of other nutrients too, such as amino acids and fats; it’s not just sugar they crave.

Here’s where the myth that sugar fuels cancer was born: if cancer cells need lots of glucose, then cutting sugar out of our diet must help stop cancer growing, and could even stop it developing in the first place. Unfortunately, it’s not that simple. All our healthy cells need glucose too, and there’s no way of telling our bodies to let healthy cells have the glucose they need, but not give it to cancer cells.

There’s no evidence that following a “sugar-free” diet lowers the risk of getting cancer, or boosts the chances of surviving if you are diagnosed. 

And following severely restricted diets with very low amounts of carbohydrate could damage health in the long term by eliminating foods that are good sources of fibre and vitamins.

This is particularly important for cancer patients, because some treatments can result in weight loss and put the body under a lot of stress. So poor nutrition from restrictive diets could also hamper recovery, or even be life-threatening.

A sticky end for sugar research?

Although there’s no evidence that cutting carbohydrates from our diet will help treat cancer, important research has shown that understanding the abnormal ways that cancer cells make energy could lead to new treatments.

Back in the 50s, a scientist called Otto Warburg noticed that cancer cells use a different chemical process from normal cells to turn glucose into energy.

Healthy cells use a series of chemical reactions in small cellular ‘batteries’ called mitochondria. The Warburg Effect, as it was dubbed following Otto’s discovery, describes how cancer cells bypass their ‘batteries’ to generate energy more rapidly to meet demand.

This shortcut for making energy might be a weakness for some cancers that gives researchers an advantage for developing new treatments.

Firstly, it opens up the potential for developing drugs that shut down cancer cells’ energy-making processes but don’t stop healthy cells making energy. And researchers are testing drugs that work in this way.

Secondly, the abnormal processes in cancer cells can also leave them less able to adapt when faced with a lack of other nutrients, like amino acids. These potential vulnerabilities could lead to treatments too.

But these approaches are still experimental, and we don’t know yet if treatments that starve cancer cells are safe or if they work.

It’s certainly not grounds for cancer patients to try and do it themselves by restricting their diet during treatment – and going back to our earlier point, it could be dangerous to do so.

If sugar doesn’t cause cancer, why worry about it?

Cutting out sugar doesn’t help treat cancer, and sugar doesn’t directly cause cancer. Why then do we encourage people to cut down on sugary foods in our diet advice?

That’s because there is an indirect link between cancer risk and sugar. Eating lots of sugar over time can cause you to gain weight, and robust scientific evidence shows that being overweight or obese increases the risk of 13 different types of cancer. In fact, obesity is the single biggest preventable cause of cancer after smoking, which we’ve written about many times before.

It’s added sugar we’re mainly concerned with when it comes to weight gain, not sugar that is naturally found in foods like fruits and milk or healthy starchy foods like wholegrains and pulses (which people should be eating more of*).

How can I cut down on added sugar?

The easiest way to lower your added sugar is to cut down on sugary drinks, which are the largest source of sugar in the UK diet.

Most sugary drinks, such as fizzy drinks and energy drinks, have more than the recommended daily maximum amount of added sugar in one serving alone. And while these extra calories promote weight gain, they offer no other nutritional benefits.

Multiple cues push us as customers to stack junk food into our shopping baskets, even if we weren’t planning to

– Professor Linda Bauld, Cancer Research UK

Other obviously sugary foods such as sweets, chocolate, cakes and biscuits are all best kept as treats too. But some foods that have hidden high amounts of added sugar may surprise you. Some breakfast cereals, ready meals (including ‘healthy’ ones), pasta sauces and yoghurts can have shocking amounts of sugar added to them. Reading nutrition information labels and checking the ingredients list can help you choose lower sugar options.

While there are steps you and your family can take to cut down on added sugar, making these changes can be easier said than done. And it’s here that governments need to lend a hand.

“Multiple cues push us as customers to stack junk food into our shopping baskets, even if we weren’t planning to,” says Professor Linda Bauld, our cancer prevention champion based at the University of Stirling. “That’s why we want the Government to help create a better food environment where the healthy choice is the easy choice for everyone.”

We’re delighted that the sugar tax has just passed through the House of Commons. It could prevent millions of cases of obesity, therefore obesity-linked cancers in the future, by reducing the amount of sugar the nation consumes in fizzy drinks.

Another area we’re watching closely is the Government’s plan to reduce the amount of sugar in the types of foods that are very popular with children.

No sweet endings

The story about sugar and cancer is complicated.

On the one hand, sugar itself doesn’t cause cancer, and there’s no way (at the moment) of specifically starving cancer cells of glucose without harming healthy cells too.

There’s also no evidence that adopting a diet very low in carbohydrate will lower your cancer risk or help as a treatment. And for patients, getting adequate nutrition is important for helping their bodies cope with treatment.

But we’re concerned about the amount of added sugar people are consuming because it’s promoting weight gain. And being overweight or obese increases the risk of least 13 types of cancer.

So the take home message is that although banishing sugar won’t stop cancer in its tracks, we can all reduce our risk of getting cancer by making healthy choices, and lowering the amount of added sugar in our diets is a good way to help maintain a healthy body weight.

Emma

*While foods like fruit, milk and healthy starchy foods are high in carbohydrate, they have other important nutritional benefits. We should all be eating more whole fruits, vegetables, wholegrains and pulses as these nutritious foods are also high in fibre – this not only helps your body digest the natural sugar more slowly (which helps you keep a healthy weight), it also reduces the risk of bowel cancer.

Comments

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Emma September 5, 2017

Hi John,
Thanks very much for your message.

You’re correct, PET scans work by measuring how quickly cells use glucose – cancer cells consume glucose more quickly than most normal cells which shows up in scans.

This article was focused on sugar in our diets and the risk of developing cancer in the first place. But researchers are looking very hard into the situation for cancer patients, because some small studies have suggested that having a diet high in sugar might help some types of cancer grow and spread (here is an example http://www.nature.com/bjc/journal/vaop/ncurrent/full/bjc2017272a.html). But this field of research is still at a very early stage and we’re a long way from knowing whether either reducing sugar consumption or treatments that stop cancer cells using getting and using sugar will benefit cancer patients.

Lots of foods contain carbohydrate in some form – either as a simple sugar which your body can absorb and use quickly, or a more complex polysaccharide (a long chain of sugars) that your body needs to break down before using it as fuel. Fruits and starchy vegetables (including potatoes, peas, beans and corn) contain carbohydrate, but they are much lower in sugar than obviously sweet foods and sugary drinks and have other nutritional benefits (for example providing a good source of fibre, vitamins and minerals) so it’s a good idea to get your 5 a day. And there’s no evidence that other sweeteners help cancer develop or grow.

During chemotherapy it’s really important to make sure you get enough calories to help your body cope with treatment, so please talk to your doctor if you are considering any significant dietary changes.

We wish you all the best for your treatment,
Emma, Cancer Research UK.

John Bailey September 1, 2017

This article causes some concern for me. When I was injected with radioactive glucose at a recent PET scan, the site of tumours was inferred by wherever the glucose gathered. Isn’t this an indicator of thefact that cancer cells greedily consume sugar? I do realise that every cell in the body needs sugar for energy production, but it is naturally present in fruit and vegetables.

Perhaps it’s the refined stuff that the body hasn’t evolved itself to handle adequately? I’m really concerned at the moment, because I would not like to think that I’m providing the body with unnecessary sweeteners thinking that they’re fine, when in fact they’ll be supplying the fuel that will nourish the cancer stem cells’ fermentation.

I dread another course of R-CHOP therapy for a possible recurrence of non-Hodgkins.

Randy Force August 28, 2017

Rubbish. Inaccuracies abound in this article. Just one for example. The body doesn’t convert fat to glucose. It converts it to ketones. Other than blood, CNS, and cancer cells, everything in your body is perfectly happy with ketones as a primary fuel source.

Xin-Hai Li August 27, 2017

Very interesting thinking to find the abmormal growth mechanism of cancer cells. Suggest to think about why the cancer cells grow very slowly with the aged people (around 80 years old) while they grow very rapidly among the young patients.

Kevin Nengia August 11, 2017

As far am concerned sugar is a big factor in cancer growth and spread. I agree that that almost all the food(starchy foods) have sugar but food fibre takes time to be absorbed in the body and is more healthy than other sugars. In addition, taking moderate sugary foods and carbohydrate is key in cancer recovery, my wife’s breast cancer case opened my eyes.
This report is business oriented to promote conventional treatment. If I may ask is science the only way of knowing?

Share Valleau August 8, 2017

This is irresponsible reporting. You have no citations, and you cannot possibly promote the idea that sugar is not bad for you, obesity is. I have done extensive research and have survived three cancers without chemo or radiation. After surgery, I credit faith, diet (including organic eating), stress alleviation, exercise, beneficial herbs and knowledge. The only way to effectively fight cancer is to make one’s body an inhospitable host for it to take root and spread. Cancer proliferates in people with sugary diets, regardless of weight.

Emma Smith August 7, 2017

Hello Shelagh,
All sweeteners are tightly regulated and rigorously tested for safety by the European Food Safety Authority (EFSA). Plenty of research has been done on steviol glycosides (a ‘natural’ sweetener) and in 2010 EFSA reviewed all the available evidence, and concluded that they are not linked to cancer and have set guidance for the food industry on how much to use in food and drinks. There is also strong evidence that artificial sweeteners, such as aspartame, do not increase the risk of cancer.
Best wishes,
Emma, Cancer Research UK

David Bastow August 5, 2017

Cancer research is all about treatment and not the cure. The treatments are surgery, drugs, chemo and radiation. All of these come with a high price tag and do NOT cure cancer. Thousands of people have CURED cancer by dietary changes. No research is being done on this because there is no money in it ($$$). This is tragic and disgraceful.
I am angry!!

Shelagh Shields July 27, 2017

What about truvia, and steviol glucoside? Are they Ok? Simple answer please. Thanks

Rajeev Samuel July 26, 2017

All lies – lions and tigers don’t require “Glucose”

Sean Andrews July 25, 2017

How about you take a look at this article that shows a direct connection with sugar consumption and cancer.
https://www.google.ca/amp/www.foxnews.com/health/2016/01/06/study-links-sugar-to-cancer-how-to-reduce-your-risk.amp.html

Gail Keating July 24, 2017

Thankyou so much for the sugar article. So easy to understand and so balanced. I shall spread it around as it is so difficult to get accurate and credible information once the media has hyped a topic.