There is a lot of confusion about sugar and cancer. 
There are many different types of cancers, with different characteristics. One thing most cancer cells have in common, though, is that they use only sugar (in the form of glucose) for fuel and not fat. Many of them have the basic machinery needed to burn fat for fuel, they just don’t. Its called the Warburg Effect.
In an attempt to use this defect in the fight against cancer, researchers are trying both calorie restriction and very high-fat, very low carbohydrate diets. The theory is that we can starve cancer cells if we deny them their preferred fuel. Our bodies can use fat and some proteins to make molecules called ketones and use them for fuel, and the hope is that cancer cells can’t.
A client with cancer called me the other day, when she got on the scale and saw 97lbs. She is 5’7” and should weigh significantly more than that. She was frustrated and afraid, she was trying to get her weight back up after chemotherapy, not lose more.
It turns out a couple of friends had given her a book, written by a physician, promoting this very low carbohydrate, high fat diet to fight cancer. This is called a ketogenic diet, and replaces the carbohydrates in our diet with fat. She wasn’t eating much, because fat dampens our appetite and really how much coconut oil can you eat in a day? She was unintentionally starving herself in an attempt to get well.
I started her on a nutrient-rich diet full of vegetables, fruits, whole grains, legumes, nuts, and healthy oils. Within a week she had gained three pounds and regained most of her energy.
Even though her experience was a disaster, I wanted to know why any physician would promote this diet. Was there new research I hadn’t seen? What does the science say about a ketogenic diet and cancer? Luckily I teach at Chapman University, with access to their extensive research library.
I found absolutely no evidence that a ketogenic diet is effective against cancer. Zero. None. There are some nice theories, a few small, poorly designed studies with mediocre results, and absolutely no evidence in human beings that this type of diet will help anyone get well.
This is what makes me crazy. I don’t know if people just want to make a buck selling the latest fad, or if they really believe in their theories enough to promote them before research has proven them true. Either way, they are hurting people.
Even a large tumor uses a relatively small amount of glucose compared with a whole person. If a 150-pound adult eats an average of 200 grams of carbohydrate a day, and their liver makes another 200 grams (an average amount) that is 400 grams of glucose used by that person in an average day. A one-pound tumor uses about 10 grams of that glucose in a day. That’s just 4% of the total glucose used by the body.
We can reduce the amount of glucose available to cancer cells by avoiding added sugars, alcohol, and refined carbohydrates. Using healthy oils instead of saturated fats helps insulin get glucose into our muscle cells, where the cancer can’t use it. All while getting the nutrients our immune systems need to stay healthy. We have lots of data showing people who eat well during treatment do better. When I ran that literature search I found over 800 studies.
If science shows that following a ketogenic diet for the short term treatment of cancer works, I am all for trying it. In the meantime, staying strong and healthy enough for treatment is the best strategy to beat this disease.
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