Changing your diet to beat cancer

Changing your diet to beat cancer

Your doctor, oncologist or nurse are completely wrong when they say that there is no point in changing your diet to help you survive longer or even beat cancer; the main reason for their error is that they have little or no understanding of the microbiome. 

UK Hospital oncology Departments are stuck in a dietary time warp  

To this day, after writing about cancer for more than 22 years, after researching drugs, diet, medical recommendations and more, I find that UK Hospitals still have not changed a jot. They are still locked in a time warp. The misinformation being uttered on the subject of diet and cancer is widespread, and in some cases downright dangerous.

It can also be belittling. "There's no point in you changing your diet if you have cancer. It will make absolutely no difference to your survival."

'Waste of time, you stupid patient' can be the translation of these utterances by the oncology team.

No, it's the oncology team that are at risk of looking stupid. If you make sweeping statements that are untrue, in the modern world it's easy to find out that you are wrong and when that happens you lose trust and credibility for anything and everything you say. 

At CANCERactive, I fear we know far more than they do. Do they realise that the colourful Mediterranean diet (our Rainbow Diet - first launched in 2005) is now recommended in seven or more Hospitals in the USA?

Let's start with something simple: I talked to a CANCERactive patient who had lost all her finger and toe nails and all her hair while taking Paclitaxel. Her oncologist had told her not to take any of those dodgy supplements.  When I asked her about her diet she told me that started her day with a whole grapefruit. Through CYP3A4, grapefruit can INCREASE the serum concentration of Paclitaxel. This holds true for Dexamethasone, Prednisolone, Atorvastatin and Amlodipine - all commonly used by cancer patients. Why didn't someone in the oncology team tell her to change her diet instead of making inaccurate claims about her supplements?

Hospitals continue to offer patients sugary, milky tea and chocolate biscuits or cake when they are having their chemotherapy. On every floor there are fizzy soft drink machines. They are living in denial when it comes to sugar consumption.  

Research published today explains that sugar consumption damages the DNA repair gene. Yes, it's potentially dangerous to feed a cancer patient sugar.

Yet some chemo drugs are given IV to patients from bags containing sugar; while the common steroid dexamethasone sent one CANCERactive patient's blood sugar up tenfold with fatal consequences. 

Telling people that there's no evidence that sugar plays a role in cancer is dangerous misinformation. Bloggers for Cancer Research UK and other skeptics say that there's no evidence sugar feeds cancer (when there's rather a lot), and then provide absolutely no research evidence themselves that it doesn't. 

And what about fat consumption? Later we'll tell you that high blood fat levels drive metastases; while a woman on a low fat diet with breast cancer or ovarian cancer increases her survival times. And how switching from saturated fat (e.g. dairy and coconut oil) to unsaturated fat (e.g. extra virgin olive oil) increases survival times.

But let's go beyond mere research results; why do sugar and bad fat consumption promote cancer, along with processed, refined and other poor food choices?  

One big word. INFLAMMATION.

And, in the majority of cases, what is the root cause of the inflammation?

The foods we eat and our MICROBIOME

People who develop cancer have built a body conducive to cancer. To stand any chance of beating cancer, they need to build a body conducive to health. Let's follow the research and explore the facts:

1. Following a good diet and exercise plan can increase your survival and even prevent a cancer returning.

In 2012 the American Cancer Society released their extensive report on complementary cancer therapy research since 2006. They were absolutely clear, a good diet and exercise were the top two factors that could increase your cancer survival time, with weight control coming third.

They then set out to test these findings. In a 7-year study on stage 3 Colorectal cancer patients, all of whom had had surgery and chemotherapy. Those who stuck most closely to the diet and exercise guidelines had a 31% longer survival and 42% less death in the seven years. Dear oncologist, do you know of a drug that can give figures this good?

The National Cancer Institute, the Government cancer body in America, in 2012 summarised all their previous research on preventing cancer recurrence. Dr. Young S. Kim (head of cancer and nutrition at the NCI) showed that a poor diet would encourage the re-growth of a cancer tumour after chemotherapy had decreased tumour size, but that eating a good diet, including certain natural compounds like curcumin, piperine, vitamin E and A, genistein, B vitamins like choline, theanine, sulphoraphanes, EGCG (from green tea) and resveratrol, could stop the cancer tumour re-growth.

Indeed, she went on to say in the research report that if you could not eat the foods containing these compounds, you could obtain these beneficial bioactive compounds from quality supplements.

88% of people on diagnosis with cancer are deficient in Iodine, causing low cellular oxygen, poor cellular metabolism, fatigue, even anaemia. Eating more seafood, or taking sea kelp pills would help.

40% of women are deficient in magnesium. Magnesium levels are dependent upon diet but further eroded by chemotherapy, yet they are essential to a healthy liver. A Rainbow Diet is high in magnesium. Of course It might be easier to supplement daily during chemo. 

Leeds University Medical School showed that people who had had CRC due to polyps and wanted to reduce the risk of a recurrence could take a concentrated fish oil of 3000 mg to improve their personal chances of survival. The fish oil reduced inflammatory polyps and patients survived longer.

Fish oils in 3 studies have also been shown to reduce the risk of cachexia. The fear of cancer patients dying from cachexia, is what makes the oncology team tell patients to eat sticky buns, cheese rolls and other rubbish foods - aren't they actually suggesting that patients change their diet to increase their survival times? Unfortunately, their sugary, high fat suggestions are misguided. People who take fish oils don't need the poor food choices.

2.1 Sugar consumption causes the immune system to go into a 'temporary coma'.

Sugar consumption puts the immune system into a 'temporary coma'. This was not our phrase but came from a review on the effects of sugar on the body by the journal Scientific American. So much for the chocolate cake and tea and biscuits diet.

Suppose you were having immunotherapy IV. Do you think it's a good idea to put your immune system into a temporary coma. while having the IV?

We know that consuming a glass of orange juice sourced from a supermarket carton will put your immune system down for around 90 minutes, as will a home made fruit smoothie - however delicious. What of the Coca Cola from the Hospital vending machine? Do people recovering in a hospital bed benefit from an immune system in a temporary coma?

2.2 High blood fats disrupt the immune system for longer!

If you have high blood fats, you will damage your Cytokines and Natural Killer cells for much longer. 

And adipose tissue - your fat store - has now been shown to act like an endocrine gland. It provides hormones that disrupt the immune system (1).

Don't you need a good immune system to fight cancer and increase survival - isn't this the whole point of the new immunotherapy drugs? Won't a good immune system increase your chances of survival?

High blood sugar and high blood fats damage the immune system. Full stop.

3. Sugar, Fat and cancer

And then we come to the cancer itself. Cancer tumours, by and large, NEED sugar to grow. Be clear, all cells can use sugar, but cancer cells NEED sugar. 

CANCERactive has a detailed review of research - 20 links between sugar and cancer. Twenty pieces of evidence on how common sugar is used to form and then grow a cancer. Are all the Professors and scientists wrong? In one research study, Dr. Craig Thompson, President and Chief Executive of Memorial Sloan Kettering Cancer Center showed that the gene, AKT, promotes cancer by signaling what a cancer cell should ‘eat’ in about 80 per cent of cancers. “When an AKT protein is placed inside a cell, it does what any single-cell organism would do - IT JUST STUFFS ITSELF WITH GLUCOSE", he said.  Is it right to that an oncology nurse in the UK misinforms a patient that sugar doesn't feed a cancer? Where's the Cancer Research UK bloggers counter evidence to this?

Apart from damaging the immune system and feeding cancer, sugar consumption increases insulin levels, which drive INFLAMMATION through the production of eicosanoids (short lived hormones) via the COX-2 pathway. This is known to help cancer spread.

When cancer tries to spread, it mainly goes into the lymph and those cells switch to burning fat. Cancer needs fat to travel and puts on a backpack of fat for the journey; fat also makes cancer cells more aggressive. Cancer also needs lots of fat for all those new cell membranes and fat aids angiogenesis. And cancer prefers saturated fat (coconut oil, dairy, seed oils) to unsaturated fat (olive oil, walnut oil). The type of fat you consume is critical to the spread of cancer. We also have many research studies on this.  

High blood fats also cause INFLAMMATION, and inflammation is known to cause immune and genetic changes. A University of California Riverside study (2) demonstrated that high bad-fat diets affected genes, not only linked to obesity, but to colon cancer, irritable bowel syndrome, a weaker immune system and brain function. The researchers fed mice a high fat diet over a 24 week period using coconut oil and soybean oil. There were significant genetic changes but also an increase in levels of the pathogen E coli, and a decrease in pathogen suppressor bacteria Bacteroides. If you are thinking of a Keto diet, think again.

For most cancers, patients on a low fat diet survive longer and people with high blood fats, develop more metastases and survive least. For example, women with breast cancer who switch to a low fat diet are 22% more likely to survive 10 years than those don't change their diet. Yes, changing their diet increases their survival.

High blood sugar and high blood fats can help spread cancer. Full stop. Low good fat diets are the way to go, if you have cancer.

Oncologists should be encouraging patients to reduce their empty sugar and saturated fat consumption, not discouraging them from making any changes to the diet that caused their cancer.

4. And then there's homocysteine 

 Let's move on from common sugar and fat.

Hands up who knows about a compound called homocysteine. 

Well Hospitals should know a lot. Elevated Homocysteine levels are associated with cancer, diabetes, heart issues and many neurodegenerative diseases like dementia, Parkinson's and Alzheimer's (10). This is rather old news actually, we've covered it quite a lot before. Elevated Homocysteine levels are also associated with Colorectal cancer (11). 

What does elevated homocysteine do? It can cause INFLAMMATION. But It is also  linked to higher methylation and increased levels of histone production. Histones can block your DNA-RNA messaging system. That fits with the conclusions of Christine Mayr and her laboratory at Sloane Kettering when they found no new mutations in your DNA rather that in cancer you had produced unfit for purpose messages. She told the world the copying process had gone wrong when you developed cancer. She won the prestigious NIH award for the year.

Of course it's an inconvenient truth. Rather that a fundamental and irreversible sequence change in your DNA, you've a metabolic problem in cancer. Homocysteine builds up, and you can reverse it and the diseases. Just change your diet. Professor David Smith showed in a 12-country study on Dementia that fish oils and a B complex could do that. So why not change your diet and consume more oily fish and whole grains? )It will also help if you have a strong microbiome) 

Bizarrely, the BBC  had a programme featuring people who ate a daily curry and a London University professor monitored the results. Yes, consuming turmeric in a curry daily reduces homocysteine levels reversing a main driver of cancer. And here's the thing. Supplements like Berberine reduce homocysteine, whereas that commonplace drug, Metformin, prescribed by doctors and even some oncologists, increases Homocysteine levels.

Foods containing zinc - fish, shellfish, pulses/legumes (lentils etc) nuts (but not peanuts), and seeds; and foods that boost your glutathione levels - greens, onions, leeks, garlic non-hormonal whey protein and flaxseed will also lower homocysteine levels.

5. To beat cancer you need a strong microbiome.

The Human Microbiome Project was a huge American study. 40 Medical Schools, 200 scientists, 3 years, $178 million. And the overall conclusion was that your gut gets ill first, then you get ill. And, you can't get better until it gets better. This finding came roughly 2500 years after that man name Hippocrates said the same. And, to think, doctors swear the Hippocratic oath?

The microbiome contains more cells than you have. It makes compounds you need, but can make compounds that damage you. It has a major impact on your metabolism and your levels of inflammation, the immune system, cancer recurrence and survival times.

The aim at CANCERactive has always been to increase a patient's personal odds of survival. When they built a body conducive to cancer, our role is to help them build a body conducive to health.

We believe you will increase your personal odds of survival by building your new body from the gut outwards.  

What we know is that before any chronic illness the volume and diversity of your microbiome falls, and that's one of the major reasons you get sick. Loss of bacteria causes a decline in your adaptive immune system. This is the system that makes your antibodies and you make antibodies to all the different bacteria in your gut every minute of the day. Loss of good bacteria also allows the bad to come out to play. and this increased imbalance is a big factor in cancer.

Loss of the good causes a loss of helpful compounds to be made - for example, serotonin, vitamin K and B vitamins. There are also three groups of bacteria each producing a short-chain fatty acid. And these three compounds, butyrate, propionate and acetate, pretty much control your metabolism. Guess what? You only make these compounds if you feed your bacteria THE RIGHT FOODS. 

For example, in almost all cases of colorectal cancer, the bacteria making the short-chain fatty acid butyrate have been lost. Butyrate actually kills off colorectal cancer cells as they form in the gut wall. Diet - such as one high in pectins, and particularly a high soluble fibre diet (pulses, nuts and seeds, oats and vegetables) - can restore good numbers of the bacteria that make butyrate - it then activates your vitamin D, heals the gut wall, attacks forming colorectal cancer cells and is highly ANTI-INFLAMMATORY. .

The microbiome has a crucial role in every cancer. There's a gut-lung axis, a gut-bone marrow axis, a gut-brain axis, a gut-skin axis etc. etc, For example, we know that in brain cancer, the gut has stopped making an ANTI-INFLAMMATORY compound that stops astrocytes becoming inflamed.

Hardly anybody I know has heard of Urolithin A. It is a very important compound made only in the gut. Recent research shows it is anti-inflammatory, boosts the immune system alongside CAR-T immunotherapy, can reduce colorectal cancer tumour growth, restore p53 the tumour suppressor in prostate cancer, it ensures healthy mitochondria, and is anti-ageing. You can only make it in your microbiome from ellagitannin - found in pomegranate, berries, walnuts. Consume none of these founds and you will make no Urolithin A. At least 60% of the population has no Urolithin in them - this makes them weak and subject to illnesses including cancer. They can increase their survival, longevity and reduce inflammation by eating the right foods.

Most importantly, in research (9) with mice and CRC, Urolithin A, reduced the number of tumours, the size of tumours, improved the immune system and increased survival. Eating the right diet increased survival times.

You lose the good and increase the bad - We know that many women with breast cancer have often lost all their Lactobacillus members and often have a heightened level of E coli infection. We know in lymphoma that no one with the disease has a bacterium called Lactobacillus johnsonii. We know that people with colorectal cancer all have a pathogen called Fusobacterium, a bacterium from the mouth; we know that people with pancreatic cancer all have a yeast with a carcinogen on its surface called Malassezia. Would it not be a good idea to try to fix this? A sugar-rich diet can feed your yeasts and E coli, a good diet can fix yeast, E coli and Fusobacterium infections. Simple foods such as garlic, oregano, cinnamon and fennel can make a big difference in eradicating these infections.

Let's turn this on its head.

Do doctors and nurses in hospitals have any idea how much damage antibiotics cause? We've covered the research showing antibiotics and Proton Pump Inhibitors should never be used with immunotherapy drugs because they damage the microbiome and give poor results. In one study on Bone Marrow Transplant, one group given a Fecal Microbiome Transplant, returned to 75% of 'normal' within days on finishing the treatment. When the other group was measured after a year, only 27% had returned to 'normal'. The lesson: to get a decent microbiome, the patient needs to take positive action to replenish the microbiome (5).

And, of course we have research on this. Women who rebuild their microbiome after conventional treatment finishes, survive significantly longer than women who do nothing. Indeed, if they don't rebuild their microbiome, they have more changes in their breasts and more likelihood of recurrence and lowered survival (6).

Yes, if you eat good foods you will increase your good bacteria, increase the production of anti-inflammatory compounds, increase your survival and be less likely to have recurrence.

6. Diet can nourish the microbiome, and the microbiome nourishes you

How many oncologists and nurses actually think of or mention the microbiome, when they are dismissing a patient's dietary improvements?

What if I said a probiotic pill containing members of both the Lactobacillus and Bifidobacterium families has been shown to make chemotherapy and immunotherapy more effective in at least 8 research studies?

What if I said that there is good research that the Rainbow Diet, on its own, can increase the level of the family Lactobacillus in the body? 

What if I said that increasing Lactobacillus levels lowers BMI and adipose tissue fat levels, waist circumference, and that the addition of, or increase in the presence of both Lactobacillus and Bifidobacterium families lower oestrogen levels in Er+ve women with breast cancer?

But what if I said that women consuming grapefruit, its juice, pomelo and/or large Seville oranges screw up the performance of many drugs? Or that peanuts actually contain a compound that cancer needs to make in order to spread? Do you think oncologists should suggest patients should change their diet to survive longer?

What if I said that we have something like 14 studies that all show Turkey Tail organic mushroom powder increases drug effectiveness, keeps white cell levels up during chemo and improves survival times?

Most importantly, what if I said that we have two research studies from Holland . The first - the Dutch Microbiome Project - shows that only 13% of your gut taxa are inherited. The rest come from your lifestyle, including your diet and early life exposure (7). The Researchers found more than 2800 illnesses which had 'signatures' in the microbiome membership, many of which were common between different diseases.  Your microbiome reflects your bad health - you NEED to change it for the better to stand any chance of beating the illness and diet is the main way of rebuilding the membership. 

The second study from Holland (8) showed that your health is totally dependent upon the foods your gut microbiome members receive!

If you feed a person certain poor food choices - high saturated fats, high sugar, refined, processed or packaged foods, these will increase the numbers of bacteria making highly inflammatory compounds, increasing inflammation and reducing survival times.

Whereas, if you feed patients a colourful Mediterranean diet including foods like extra virgin olive oil, oily fish and walnuts, plus soluble fibre, nuts and seeds, vegetables and berries, you produce more gut bacteria that make anti-inflammatory molecules, resulting in much better health results across all chronic illnesses?

Give patients sticky buns and chocolate cake and you will increase the bacteria that cause INFLAMMATION.

Yes, eating junk food gives you a junk body.

But eating good foods clearly REDUCES INFLAMMATION. 

Doctors measure your CRP score if you have cancer. Why? Because the more inflammation you have, the more likely the cancer will spread, and the lower will be your survival. And the lesson from this article is ...


Nourish your gut bacteria with the right foods and they will cut your inflammation and produce the compounds that nourish you.

Do you still think that changing your diet has no effect on survival times? 

Go to: The Best Foods for Gut Health


      "At last the definitive book on a diet to fight cancer". Mrs BS Devon.


Important diet articles on the CANCERactive website

So to help all readers of our web site to get started in this area, we have detailed many articles on this website about diet and cancer. Here is a list of those articles:

1. Calorie Restriction and Fasting have been shown to improve the outcome of chemotherapy and even to stop cancer progression.

The Ketogenic Diet is a variant of this where you do get to eat food - but fat and oils more than carbohydrate and protein. It is important to understand that glucose (and high fructose corn syrup) are the prime fuel of a cancer cell and you should avoid feeding your cancer!

3. Then we have Diet Therapies (Click Here) For example The Gerson Therapy, The Plaskett Therapy, The Gonzalez Therapy, The Hoxsey Treatment, the Pfeifer Protocol. These might be used as alternative therapies, but are more commonly used as complementary therapies.

4. There is a popular article entitled 12 Foods that fight cancer (Click Here)

5. And an article on 20 Herbs that Fight Cancer (Click Here)



  1. Fat: A matter of disturbance for the immune system; Alessandro Federico, et al; World J Gastroenterol. 2010 Oct 14; 16(38): 4762–4772.
  2. Impact of various high fat diets on gene expression and the microbiome across the mouse intestines; Jose Martinez-Lomeli et al; Scientific reports; 27 Dec 2023
  3. Women's Health Initiative
  4. Vitamin D regulates microbiome-dependent cancer immunity; Science 25 April 2023
  5. Fecal transplants restore gut microbes after antibiotics -
  6. An unhealthy gut helps spread breast cancer; -
  7. The Dutch Microbiome Project defines factors that shape the healthy gut microbiome; R Gacesa et al;
  8. Gut microbiome study links Rainbow Diet foods to good health
  9. Metabolite from Pomegranates may help fight colorectal cancer
  10. Disturbed homocysteine metabolism is associated with cancer; Tauheed Hasan et al; Experimental & Molecular Medicine volume 51, pages 1–13 (2019)
  11. Homocysteine and Digestive Tract Cancer Risk: A Dose-Response Meta-Analysis; Jun Xu et al;J Oncol. 2018; 2018: 3720684.


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