You may have seen foods labeled as “Keto-friendly” on your recent trip to the grocery store. Or maybe you flipped on the television and heard celebrities talking about how they follow a “keto diet.” So what is keto, anyway, and is it here to…stay?

What is it?
Keto stands for ketogenic. The premise behind the diet may sound familiar: lower carbohydrates, more fats. This may make you think of the notorious Atkins or South Beach diets. On a keto diet, foods like eggs, cheese, oil, nuts, and bacon(!) are encouraged. This puts your body into a metabolic state where it turns to fat for energy in the form of ketone bodies rather than sugars, in the form of glucose provided by carbohydrates.

Michelle Myers, MS, RD, CDN, a registered dietitian at Savor Health says “Take a low carbohydrate, high-fat diet to the extreme and that sums up the ketogenic diet. Carbohydrates are restricted to five percent of daily calorie intake. This means limiting carbohydrate intake to 25 grams per day for someone on a 2,000 calorie per day diet. Twenty-five grams of carbohydrates is the amount found in just one medium-sized banana or two slices of whole wheat bread.” -Michelle Myers, MS, RD, CDN

Keto for Cancer?
There’s been a lot of talk about the link between sugar and cancer. For example, sugar is the main “food” for cancer. All cells need glucose, or sugar to survive, including cancer cells. With this information, it could be easy to suggest that removing sugar (in the form of carbohydrates), could starve cancer, thus putting an end to its existence. But things aren’t so simple. Our bodies need carbohydrates to function – all of our cells require energy to function and your body never lets your blood glucose level drop below a certain number, so eating less sugar will just make the body use its remaining resources to produce glucose (sugar) on its own.

In terms of developing colon or rectal cancer, obesity is a risk factor. And it’s clear that a ketogenic diet can help a person lose weight (although the jury is out if weight loss can be maintained long term using this approach). Obesity is a risk factor of colorectal cancer and recurrence. Considering a ketogenic diet from this perspective, if you are overweight, then yes it does help reduce the risk of getting cancer and could be something to consider with the support of a healthcare professional.

“There are some very early data suggesting that a high fat, very low carbohydrate ketogenic diet may benefit people with certain types of brain cancer. However, much more research needs to be done and, so far, there is little to no evidence to support the hypothesis that this type of eating pattern could benefit people with other cancer types. The majority of claims regarding the ketogenic diet and cancer come from lab and animal studies, and the conclusions are difficult to translate to cancer patients. If not carefully monitored, this type of diet can have unintentional consequences on a patient who may already require additional calories and protein and should be discouraged for now unless specifically recommended by the patient’s oncologist.”

In terms of colorectal cancer treatment, there’s no research showing that a ketogenic diet can cure cancer. According to the most recent studies – more research is needed to understand if combining a ketogenic diet along with standard treatments (for example, chemotherapy, and radiation), could lead to improved outcomes for patients. For many colorectal cancer patients, diet and nutrition are incredibly important as cancer and its treatments can lead to malnutrition. Talking to a dietitian is a good way to learn about what foods to include, and which to avoid, especially as all people have different situations, goals, and preferences.

According to Myers, “There is clear evidence that diet plays an important role before, during, and after cancer treatment, however, there is no one size fits all approach as there is no one specific diet or food that can cure cancer.” Myers says it is important to remember that “Goals of nutrition change throughout the cancer care continuum. For example, during active treatment, the main goal may be to maintain adequate oral intake while managing nutrition-related side effects.”

However, the research is clear that following a balanced diet where two thirds or more of the diet comes from plant-based foods such as fruits, vegetables, whole grains, nuts, seeds, beans, lentils, and one third or less of the diet is composed of lean animal protein such as as skinless poultry, lean turkey meat, fish, and low fat or non fat dairy. This dietary pattern, coupled with exercise, avoidance of processed meats and limiting red meat intake can decrease one’s risk of colorectal cancer and recurrence as well as promote general health and wellness.

What’s the bottom line?
Diet and nutrition are hot topics in many research facilities, and the keto diet is emerging as an area of interest. But until there is clear evidence, it’s important not to get distracted by claims of a cure-all, and use caution when it comes to fad diets that eliminate food groups. Balance is often the keyword when it comes to nutrition, and many top experts now recommend a plant-based diet, low in red and processed meats (remember that the World Health Organization recently classified red meat as “probably carcinogenic” to humans) and added sugars.

For more information about nutrition, consult a registered dietitian nutritionist. To find one in your area, ask your treatment team or visit For more information on nutrition and cancer visit:


Systematic review: isocaloric ketogenic dietary regimes for cancer patients Erickson, N., Boscheri, A., Linke, B. et al. Med Oncol (2017) 34: 72.
Hopkins BD, Pauli C, Du X, et al. Suppression of insulin feedback enhances the efficacy of PI3K inhibitors. Nature. 2018;560(7719):499–503.
“The Use of Diet in the Treatment of Epilepsy,” Epilepsy & Behavior, February 2005,
“Effect of Low-Carbohydrate High-Protein Diets on Acid-Base Balance, Stone-Forming Propensity, and Calcium Metabolism,” American Journal of Kidney Diseases, August 2002,

3 thoughts on “Keto Diet and Colorectal Cancer

  1. After treatment what kind of foods can we eat because most of us that have had lower anterior resection surgery cannot eat raw fruits or veggies. If eating a diet in these groups are to help prevent cancer, what can we eat to get the right nutrition to prevent reoccurrence?

  2. There’s no diet that can cure cancer. There’s also no good research that shows that any eating plan, like a vegetarian diet, for example, can lower the chance of cancer coming back. Your best bet is to stick with a balanced diet with lean proteins, fruits, vegetables, whole grains, and low-fat dairy.

  3. “However, the research is clear that following a balanced diet…” No, it really isn’t. There has been insufficient research on any nutritional strategy for preventing or treating cancer, and such studies ar enot being adequately funded, in my opinion. This includes the “plant-based” approach, “balanced” diets and keto. There is some, but inconclusive, evidence, for a number of approaches, including keto. There is no evidence of danger in a properly approached keto diet. Most of the arguments against it simply state that it is too hard to do, but not everyone finds that to be the case. It should be supported by the oncologist and preferably also a nutritionist, but has been used for other medical conditions for many years and is well understood. Agreed that no one should present any diet as a “cure-all” but so long as nutritional status is not deteriorating, it seems reasonable for patients to try various approaches to see if any can help them tolerate or minimize the side effects of their primary treatment. Keto does this for some people, but I suspect that different approaches work best with different people’s biological make-up. BTW, one of the cited references is about low-carbohydrate, high-protein diets, but high-protein diets are not ketogenic.

Leave a Reply

Your email address will not be published. Required fields are marked *