The Ketogenic Diet and Cancer

The ketogenic diet has been all the rage in the media lately as a potential weight loss diet or as a strategy to reduce cancer cell growth, but is it really safe or evidence-based? I’m about to nerd out with you, buckle up.

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What is the ketogenic diet?

The ketogenic diet (KD) is a high fat, moderate protein, and low carbohydrate diet. Americans generally consume a diet high in carbohydrates (50-75%). The KD diet requires careful calculation to ensure the ratio of fat to protein/carbohydrates is 4:1. When this ratio is achieved, metabolic pathways shift the bodies’ use of glucose as its primary source of energy to fat or ketones (metabolites of fatty acid breakdown). During this process called ketosis, the body starts to metabolize ketones to provide fuel for bodily functions. Examples of high carbohydrate foods that are limited on this diet include sweets, bread, pasta, juice, fruit, and starchy vegetables. Examples of high fat foods that would be included in this diet may be avocado, olive oil, nuts, nut butters, heavy cream, and butter.

This diet has classically been used to treat epilepsy in children and most recently in adults. In regards to cancer, the ketogenic diet has been of particular interest in the treatment of brain tumors, such as glioblastoma multiforme (GBM). However, there has also been interest in its overall treatment of any cancer. Because the brain and cancer cell’s preferred fuel source is glucose, the theory is the KD may alter the metabolism and reduce growth of brain tumor cells and possibly make it more sensitive to treatment (chemotherapy and radiation).

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What we currently know

  • The use of the KD diet is safe and feasible as an adjuvant therapy, but requires frequent lab testing and supervision by a dietitian and physician.
  • The KD diet should be administered over at least 3-4 weeks to see any potential benefit or improvement.
  • Quality of life and current tolerance to cancer treatment should be taken into consideration before starting this diet. If a patient is already having difficulty maintaining their weight or sustaining nutritionally, the ketogenic diet may only exacerbate cancer cachexia and an individuals ability to tolerate treatment. A patient’s safety should always be priority numero uno.
  • Animal-based studies and some human studies have shown promising, yet inconsistent results in reduction of tumor growth with the ketogenic diet, especially with brain cancers.

Questions that still need answering-

  • Does every type and subtype of cancer respond the same way to the KD diet? It’s important to remember that not all cells in the body respond the same way and same goes for cancer cells.
  • What’s the exact dosage or ketogenic diet regimen that is most effective? For example, what exact ratio of fat to carbohydrate will be most successful in reducing tumor growth?
  • What are the specific markers or signals that indicate the ketogenic diet is working as it pertains to cancer? In the case of epilepsy, effectiveness can be seen by a patient not having seizures as a result of successful ketosis, however this would be more difficult in cancer. It may require more frequent CT scans and imaging to check on the growth or lack thereof of tumors as a response to the ketogenic diet. With insurance companies already getting a little iffy with providing coverage for reimaging, this may be a challenge.

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Other things to consider-

  • Side effects: constipation, fogginess, lightheadedness, and fatigue
  • Better research is needed:
    • Gold standard: Double-blinded, randomized controlled clinical trials
    • Studies specific to cancer type and subtype
  • Good news! Currently, there are several clinical trials and studies ongoing to help address the questions requiring answers.

Takeaway: As an oncology dietitian, I am very excited about the potential of the ketogenic diet being used as a measurable medical nutrition therapy in cancer treatment. But just like any prescription drug or chemo treatment, this needs to have substantial supporting evidence and testing to ensure the treatment is safe and effective. More to come on this topic. Stay tuned…

-EAW