Sugar and cancer - The myth exposed

Cancer cells in tumours need sugar, lots of it; and sugar consumption also causes inflammation, damages the gut microbome, your immune system and even your DNA repair genes.

You may have heard your oncologist say that ‘sugar feeding cancer is just a myth’, Or even a nurse saying that ‘it's all mumbo-jumbo’, or ‘nonsense’. Only last week I had patients told exactly this. Unfortunately, it just shows complete ignorance on the part of the oncology team. But it could be politics.

1. Cancer cells need glucose

It's called the Warburg effect. Otto Warburg showed that cancer tissues fermented glucose into lactic acid for fuel and the lower the oxygen, the more the fermentation. He won a Nobel prize for this.  If your oncologist says he's never heard that sugar feeds cancer, he may just be poorly educated (1).

Despite the Nobel prize, the Warburg effect has some scientists claiming it was more an opinion than science. The problem is that people in the field of oncology have been taught consistently that cancer is a genetic disease. The sun spins round the earth. You have mutations in your DNA - you need to cut them out, blow them up or burn them. Warburg was saying that cancer was a result of metabolic changes. That runs counter to the whole narrative of the cancer industry. So the industry decries Warburg’s metabolic theory.

Unfortunately, at least three studies have supported this ‘Cancer is a metabolic disease’, not a genetic one, argument. 

First, we had the St Jude’s mouse study where nuclei of mice who had rampant cancer replaced that of  mice embryos. If the disease were genetic, you would expect lots of baby mice with cancer. Perfect healthy mice were formed; nothing bad had been carried by the nucleus.

Then we had Stanford Medical School conducting research (2) on inherited mutations (3-7% of patients). After showing the other strand in the DNA double helix was unaffected and had no changes made in it when the human developed breast cancer, they concluded that even if you had a mutation it had no effect on survival times.

Finally, we had Christine Meyr of Sloan-Kettering showing there was no genetic mutation in the DNA; It was the copying process that has gone wrong. She too won a major award from the NIH,, but no one  in the cancer hierarchy quotes her research. It's embarrassing because she is showing that the Somatic theory of cancer is wrong. The sun does not spin round the earth.

If you agree that cancer needs sugar, you are agreeing that it’s a metabolic disease, not a genetic one. Deep down, it’s propaganda.

2. Sugar puts your immune system into a ‘Temporary coma’

We have done a lot of work at CANCERactive on how sugar feeds cancer; for example see 20 links between sugar and cancer. The majority of these links are from Top Professors in top western medical schools. They can't all be idiots. 

Who is the nurse that denies all their research?  In the article you will see the first section is all about how sugar consumption damages your immune system. 

But you don't have to rely on CANCERactive. Scientific American did a massive review on sugar's role and showed that eating sugar may put your immune system into’ temporary coma’. Having freshly squeezed orange juice for breakfast or honey on toast can flatten your immune system for three hours. Now imagine what the milky sugary tea and biscuits do when you're having chemo; Or even that the dexamethasone will raise your sugar levels considerably; and that all the platinum based  chemo drugs are in a sugar solution. All these flatten your immune system as well as the Coca-Cola and Ribena from the Hospital vending machine. Sugar abounds in UK Hospitals.

Again, let’s be fair to the research. A small amount of sugar may be important to a healthy immune system, but a higher consumption can be damaging, for example to cytokines (3)

3. Sugar consumption ruins the gut microbiome

Oncologists and nurses don’t know much about the microbiome. It is really your Health Control Centre. It gets ill first then you get ill; and you cannot get better until it gets better. It has 3 times more cells hat your body; seven times more genetic material. It make more hormones, proteins and enzymes that you do. At any one moment, 38 % of the small molecules in your blood stream come from your Health Control Centre, than from the rest of your body.

Sugar consumption favours the pathogens and yeasts over the commensal (good) bacteria. This results in leaky gut, an imbalance in the Gut (dysbiosis), an increase in inflammation, and a increased risk of all chronic illnesses including cancer.

Your healthy bacteria make 3 Short Chain Fatty Acids (SCFAs) - propionate, butyrate and acetate. These are crucial to your health. Sugar consumption decreases their levels.

Sugar consumption causes untold damage to your Health Control Centre (8).

4. Sugar causes inflammation, which increases cancer risk and progression

Doctor William LI is a world renowned Harvard educated scientist who specialised in angiogenesis - the formation of blood supplies in cancer. Our own Chris Woollams is an Oxford University educated biochemist; Both will tell you very quickly that inflammation is a major root of all chronic illness, From cardiovascular disease to cancer. Yes,  invariably, insulin plays a role en route. But why do you get insulin increases? Because of poor sugar control. 

For example, sugar combines with proteins or fats to form ‘Advanced Glycation End Products’ (AGEs), which trigger oxidative stress and inflammatory pathways, resulting in more illness and a more rapid aging process (4).

Put simply, consuming too much sugar and other refined carbs is linked to inflammation in the body (5) 

Inflammation and cancer is a hugely complex and intricately controlled process, inflammation involves countless different types of cells and a fluctuating mix of chemical signals. Despite being crucial to our health, inflammation can cause serious damage to our body if it spirals out of control and is a major risk factor for cancer. 

When it comes to cancer, poor sugar control in both diabetics and non-diabetics leads to cancer formation and progression. Johns Hopkins researchers showed back in 2005 that people with higher fasting blood sugar levels were more likely to develop cancer or to die from cancer (6).

And an ASCO presentation to all top oncologists the presenters said this: ‘Chronic inflammation has been recognized as a key contributor to cancer initiation, progression, and treatment response across various malignancies’ (7).

5. Sugar consumption can damage your DNA repair genes

High glucose levels can temporarily disable the BRCA2 gene, a critical tumour-suppressor responsible for DNA repair.  A 2024 study by the Cancer Science Institute of Singapore found that high blood sugar, particularly in conditions like diabetes, leads to the accumulation of methylglyoxal (MGO), a toxic byproduct of glucose metabolism. 

MGO accumulates in cells and temporarily stops the BRCA2 gene from functioning, which can allow cancer-causing mutations to occur.

6. All Cells ‘use’ sugar

Let’s explode another myth. All cells use sugar. Although it is true, this is 100% misleading. This is another answer trotted out by the faithful to decry the sugar and cancer truth. 

It is, of course, true - all cells use sugar. All cells burn sugar. But healthy cells don’t NEED it. They can burn fats. Tumour cancer cells cannot. They only switch to fat as they move off round the body.

The ‘all cells use sugar’ statement is simply naive and flies in the face of reality. The Chief exec Sloan-Kettering, Dr Craig Thompson, told the world from his research that cancer cells are like primitive cells. They contain a protein called Akt. This has one job - to stuff the cell full of sugar. There is a huge difference between the sugar requirement of a cancer cell and that of a healthy cell. Thompson even caused cancer by feeding cells sugar in his experiments. Dr. Chi Van Dang, Director of the Abramson Cancer Center in Pennsylvania goes further. He says that cancer cells are “addicted to nutrients ... like glucose”.

Cancer cells are totally inefficient and demand much much more sugar. Without this fact, a PET scan would not work. Using radioactive sugar called 18-F, it is lighting up the sugar-avid cancer cells, not healthy cells, even though they do use sugar.  There’s a world of difference between a cancer cell and a healthy cell. It’s a difference scientists creating drugs try to exploit. Cancer cells need much, much, much more sugar than a healthy cell. They stuff themselves with sugar and even have 13 times more insulin receptors on their surface to make it possible. It's another inconvenient truth.

Go to: So How does a Cancer cell feed and spread

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References

1. 100 years of the Warburg effect - a cancer metabolism endeavour; Sarah-Maria Fendt; Cell, Volume 187, Issue 15, 25 July 2024, Pages 3824-3828

2. Women with genetic mutations fare no worse with breast or ovarian cancer, study finds; Krista Conger; Stanford Medical Research Oct 1st 2021

3. Harmful effects of high amounts of glucose on the immune system: An updated review; Navid Shomali et al; Review: Biotechnol Appl Biochem, 2021 Apr;68(2):404-410

4. Dietary Sugars and Endogenous Formation of Advanced Glycation Endproducts: Emerging Mechanisms of Disease; Manuela Aragno, Raffaella Mastrocola; Nutrients. 2017 Apr 14;9(4):385.

5. Excessive intake of sugar: An accomplice of inflammation; Xiao Ma et al; Review, Front Immunol; 2022 Aug 31:13:988481. 

6. High sugar levels increase cancer and mortality risk - Johns Hopkins Bloomberg School of Medicine

7. Chronic inflammation and cancer: ASCO 2025 update; Dosser, C., Wolf, D. & Zimmer, K. memo 18, 311–315 (2025).

8. Added sugars, gut microbiota, and host health; Yanbo Zhang et al; Gut Microbes. 2025 Dec 1;17(1):2592431.