Swapping sugars may improve cancer outcomes

Sugar Cubes Cancer

It’s one of the most dreaded conversations we all fear having with our doctors.

“I’m sorry to say this, but you have cancer.”

Practically everyone has a personal connection to someone with a cancer diagnosis, and are therefore all-too familiar with the unpleasant and sometimes unbearable side effects of chemotherapy and radiation.

What if there was a better way to treat cancer? Or a way to lower the dose of chemo and radiation required? The secret may depend on how we metabolize sugar.

A recent study showed that simply by changing the type of sugar fed to mice, from glucose to mannose, investigators could reduce cancer cell growth. (Mannose is a simple sugar — or monosaccharide — like glucose, but it is far less common in the body.) Furthermore, the study authors also showed the cancer cells become more susceptible to chemotherapy in the mannose-fed mice.

Nature: Mannose impairs tumour growth and enhances chemotherapy

Their success gives further backing to the concept that cancer cells have an altered cellular metabolism. Cancer cells depend on glucose for their fuel and have enhanced glucose uptake —the so-called Warburg Effect. Finding a safe and effective way to change cellular fuel, therefore, seems to have potential for impairing cancer cell growth and improving outcomes from conventional treatments such as radiation, chemotherapy and surgery.

One interesting caveat to the findings in this study was that only those mice with a low level of the enzyme phosphomannose isomerase saw significant benefit. It turns out, this enzyme converts mannose into fructose. It is possible that the cancer cells were able to use fructose for fuel whereas they could not use mannose.

While these are interesting findings, they may be meaningless. The most effective way to alter cellular energy supply away from glucose isn’t eating a different sugar like mannose. It’s not eating sugar at all — a combination of nutritional and fasting ketosis.

When we are in a state of ketosis, our body shifts from utilizing glucose as fuel and instead turns to fatty acid oxidation with the production of ketones. This shift, from glucose to ketones, is something cancer cells are unable to do, and thus ketosis is a potential powerful adjuvant therapy for cancer.

It seems clear glucose is the enemy. Fortunately, we all have the tools to reduce our body’s dependence on glucose.

Will this result in improved cancer treatment outcomes? We don’t have definitive evidence to say that yet.

There are, however, numerous ongoing studies to investigate this exact question, and there is reason to be hopeful. Mannose not required.

Thanks for reading,
Bret Scher MD FACC


What diet causes cancer?

‘Action on Sugar’ calls for less sugar in the UK’s food

NYC Health Department is pushing companies to cut sugar



  1. S du Toit
    Sadly my wife over a 20 year period had breast cancer in both breasts.Its not for me to comment on research done by such great scientests.What bothers me is this;sugar worse than cocaine(death prior to cancer),defrosted chicken in plastic,too much coffee,lack of sunshine,too much sun,smoking,breathing second hand smoke,breathing contamonated air.Can you please send me the name of the supplier of a tent,room,house ,place where we can live cancer free.Mars?Personally I am sick of the wonderful research by great countries which often actually achieve nothing.PS I drink one cup of coffee per day and have since cocaine is similar,added a further teaspoon.(By the by,I have never taken any drug such as dagga or cocaine ever)
  2. Lonnie Graham
    I have been followed this WOE for nearly 3 years. At the beginning of this year I was diagnosed with a Stage 3 ER+PR+ Tumour and of course feared the worse. After ungoing a Left Mastectomy my lab results came back with a very low proliferation rate and no further treatment was recommended, apart from Tamoxifan (my choice). I believe (no proof of course) that this was all due to my WOE halting this tumour in it's tracks. NED for 9 months+. Thanks Diet Doctor - I owe it all to you guys.
  3. Jim
    I have late stage 2 rectal cancer. Begin treatment chemo/radiation treatment Dec 20. Following a strict, almost zero carb, low protein diet with some intermittent fasting mixed in 18/6. I have my fingers crossed, that the radiation shrinks the tumor sufficiently so the surgeon can avoid leaving me with a permanent colostomy. Wish me luck. I will report back.


  4. Carol
    Best of luck Jim. I think you are on the right track. Have you read "Tripping over the Truth" by Travis Kristofferson or look up Prof Thomas Seyfried. Or the YouTube chanel of the Epigenix Foundation. Thank goodness for the Internet ....ordinary people can find out extraordinary things and make ourselves well.
  5. Thorsten
    Thank you for this interesting article. While I agree with you that dietary modifications (and especially the low carb high fat approach) are promising as adjuvant approaches to cancer therapy, I don't think we can safely state that (quote) "This shift, from glucose to ketones, is something cancer cells are unable to do..". There are a number of publications showing that cancer cells in vitro and in vivo are able to take up and metabolize ketone bodies, e.g. this one (DOI: 10.1093/neuonc/now088) on a rat glioma model. Obviously, we need a lot more research to fully understand the fascinating effects that a low carb high fat diet can have on tumor progression. I doubt it is safe to say that these effects are mediated by ketone bodies at this point.

    I very much appreciate your very important work and your pivotal contributions to the field. With very best wishes, Thorsten

  6. Marion
    I have cancer for the third time.Along the scar line where my breasts used to be.
    I was offered surgery ,removal of some ribs plus skin grafts to full up hole.
    Without any guarantees of a cure.To me the surgery would have been too invasive,months to recover.One year later I’m in good health,trying to keep out sugar ,very low carbs if any.My personal belief is that ketogenic diet slows down the cancer while it doesn’t cure it.I also do intermittent fasting,excercise look after myself.So far I am pleased with my decision
    How Brilliant is was the former mayor of NYC, Michael Bloomburg with this new info!

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