Chewing the Fat about the Keto Diet and Cancer


Many diets have come and gone – Low Fat, Low Carb, Paleo, Raw and many more. Right now, there is no more popular or trendy diet than the Keto Diet.  Its supporters suggest that it will help you lose weight, regulate your blood sugar, help with energy levels and some even suggest that it can improve your cancer survival.  Current research in cancer care has been limited to mainly preclinical studies (petri dish and mouse models), reports on patient case studies, and small randomized clinical trials. What does the available clinical data actually say? 

What is the Keto Diet? 

The keto, or ketogenic diet, is a high fat, moderate protein, low carbohydrate diet. It is designed to change your body’s primary fuel source from carbohydrates to ketones, which are a byproduct of fat breakdown in the liver. There are several different variations on the diet which include more or less carbohydrates – typically less than 50-130 grams of carbohydrates a day.  The classic ketogenic diet used in scientific research is the most strict, but some beneficial effects have been seen for a modified keto diet as well. 

Why would a Keto Diet help cancer patients?

Cancer cells rely on burning glucose, a carbohydrate, at much higher rates than non-cancerous cells for energy. By reducing the amount of carbs eaten and therefore glucose in the bloodstream, it is proposed that cancer cells would be stressed and cancer treatments would be more effective.  Ketogenic diets also have been shown to reduce fat mass and insulin levels, which can lead to an anti-cancer environment within the body.

What are potential positives of the Keto Diet for cancer patients? 

Importantly, in the majority of studies on this diet in cancer patients it was shown to be safe and well tolerated, with no increased serious adverse effects.  Cancer patients were able to continue on cancer treatment while on this diet, and most studies had fair to good retention rates – meaning most people found the ketogenic diet reasonable to follow for short periods of time. This was especially true for a modified keto diet, which has a more relaxed carb limit. 

For patients who are on PI3K inhibitors, like Piqray, a ketogenic diet could be quite useful. PI3K is a commonly mutated enzyme in cancer cells that binds insulin and stimulates glucose breakdown. This allows cancer cells to grow and spread quickly.  If a patient is on a PI3K inhibitor and eats a moderate or high carbohydrate diet, the effects of the drug may be limited.  A mouse model showed that a ketogenic diet increased the effectiveness of this drug in pancreatic, bladder, endometrial, and breast cancers and there is an ongoing study to see if there is a similar effect in humans. 

Other potential benefits of a ketogenic diet have been shown in for brain cancers.  Brain cancer cells cannot use ketones for energy, but regular brain cells can.  Several studies have shown positive benefits for progression free survival and tumor size in gliomas and glioblastomas, however the data overall is mixed.

A small, non-randomized study was done in Japan recently, looking at using the keto diet as an adjuvant therapy in multiple kinds of advanced cancer. This included colorectal, breast, pancreatic and non-small cell lung cancer. The 37 patients followed a strict ketogenic diet with less than 30 grams of carbohydrates per day with mild calorie restriction for up to a year of follow-up.  Though it was looking at a limited number of patients, they were able to show improved survival in multiple cancer types.  

What are potential negatives from the Keto Diet? 

One major negative that stands out for anyone looking to follow the ketogenic diet, especially the strict classic version, is that it is hard work! It requires reading food labels of everything you eat, measuring food on a gram scale and planning meals out very carefully.  Dining out or eating at a loved one’s home becomes fairly challenging, and overall it is a huge disruption to the way life is typically lived. This makes the keto diet hard to stick to long term.

Additionally, as a ketogenic diet is lacking in whole grains, dairy, and most fruits and vegetables, there is a very real possibility that a patient could develop nutrient deficiencies. Research shows that most B-Vitamins, Vitamin C, iron, calcium, potassium, magnesium, and Vitamins A, E, and K are at risk of being low when following a low carbohydrate or ketogenic diet.  These diets are typically low in fiber, which can alter the gut microbiome and make regular bowel movements challenging. It is essential that a ketogenic diet be initiated and followed only under the supervision of your physician and a dietitian to ensure it is well planned and adequate in all nutrients. 

A ketogenic diet often results in weight loss, which can sometimes be from loss of muscle and bone mass. Cancer patients are at high risk of malnutrition due to their high energy needs, nutrition-related side effects of treatment, and fatigue levels.  Inducing weight loss and restricting the kinds of foods allowed could lead to the development of malnutrition, which is known to lead to worse cancer outcomes overall.

As a ketogenic diet is high in fat, there is a risk that it may worsen cardiovascular markers like cholesterol and triglyceride levels. A meta-analysis of six randomized controlled trials was not able to detect a significant change in these markers. It is important to note that patients were being monitored by dietitian and doctors who designed and prescribed the diets to ensure that they are balanced in animal and plant sources of fat. If not planned correctly, a keto diet could easily become a bacon/cheese/beef diet which would likely lead to worse cardiovascular health.

Overall Recommendations

There is no one diet, one food, one supplement or one nutrient that can entirely cure or prevent cancer. The emerging research around the ketogenic diet and cancer is interesting and there is reason to believe it may be helpful in certain cancer types or populations. There has also been evidence that it can make a few types of cancer including leukemia and breast cancer worse, so caution must be taken. Overall, the data is not strong enough to recommend its use broadly in cancer patients.

Until more robust data is available, following a healthy, plant-based anti-inflammatory diet that is rich in whole grains, lean proteins, and brightly colored fruits and vegetables like that recommended by the AICR and the AND is going to be beneficial for most cancer patients. This diet will provide the most support for cancer patients. If you are interested in starting a ketogenic diet, please speak with your care team first so that they can monitor your condition on this diet and help you plan balanced intake to make sure you are meeting all of your nutrition needs. 

If you have any questions about the ketogenic diet or about healthy nutrition during cancer treatment, please join our community at OncoPower.  We have Registered Dietitians who are more than happy to help you on your journey. Nutrition is highly personal and you should always feel comfortable reaching out for personalized advice. We have many other qualified cancer care specialists on our platform, who are able to answer a range of questions – join and find out more!

This article is not intended to be medical advice and should not be interpreted as such. Always discuss any potential treatments with your doctor before starting. 

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