Can You Use The Keto Diet To Help Treat Cancer? Here's What The Science Says

RD & Certified Specialist in Oncology Nutrition By L.J. Amaral M.S., R.D., CSO
RD & Certified Specialist in Oncology Nutrition
L.J. Amaral is a Registered Dietitian/Nutritionist who is board certified in Oncology Nutrition. L.J attended the University of Connecticut and obtained a B.S. in Nutritional Science. She went on to get her M.S. in Clinical Nutrition and Dietetics from NYU while subsequently completing her internship to become a Registered Dietitian at Memorial Sloan Kettering Cancer Center in Manhattan.

Image by Nadine Greeff / Stocksy

The ketogenic diet has been quite the buzzword recently, and for good reason! There are many purported health benefits of the diet ranging from weight loss and lowered inflammation to improved energy and even cognition. Currently, there are almost 100 clinical trials open or about to start recruitment of patients to see if the beneficial effects of the diet are true. So what is the diet, exactly?

The ketogenic diet is a high-fat, moderate-protein, and low-carbohydrate diet. It restricts carbohydrates coming from bread, pasta, rice, crackers, sugar, root vegetables like potatoes, and most fruits. The diet is a well-established medical treatment for refractory pediatric epilepsy or for children who have seizures and do not respond to their anti-seizure medications. Its first documented use in the United States has dated back to the 1920s. Despite this, we currently have very few human studies with evidence supporting its use in different diseases, such as cancer. This, in addition to the diet getting great attention in the media, has led to a lot of confusion as to what the keto diet is and what it is not and who would benefit from it.

Can the keto diet be helpful for cancer?

The connection between the ketogenic diet and cancer has everything to do with how cells behave. In his research, Nobel laureate Dr. Otto Warburg, discovered that 80 percent of human cancer cells have an increased intake of glucose and, without the presence of oxygen, produce very little energy. This is incredibly unusual in comparison to normal energy metabolism—where a small amount of glucose yields a large amount of energy in the presence of oxygen. In other words, this guy discovered that the metabolism of most cancer cells is altered.

So where does the keto diet come in? Using the ketogenic diet, we can potentially change the tumor's metabolism by reducing the amount of glucose and other nutrients, like insulin and insulin-like growth factor (IGF-1), it gets to feed on. This can reduce the blood flow going to the tumor, making it much less favorable for cancer cells to grow.

Research has already done on this, with a recent study showing that for obese endometrial and ovarian cancer patients the keto diet helped reduce their fat mass and insulin and IGF-1, thus potentially decreasing their tumor burden. There are studies now looking at how one of the ketone bodies—compounds produced in the body when a person is on the keto diet—can actually function as an antioxidant to help minimize damage to other healthy cells.

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What type of keto diet is best for cancer?

There's an ever-increasing amount of evidence to support using the keto diet in cancer patients, specifically with brain tumor patients. We use the term "classic" ketogenic diet in our brain tumor clinic when we are talking about a 3:1 ketogenic diet. This translates to about 80 percent of total calories coming from fat, or 1,600 calories coming from fat alone for someone eating 2,000 calories a day. This specific ratio is considered to be the most therapeutic for a few different reasons. We are currently using the diet in our phase I clinical trial in patients within the first three months of a diagnosis of a type of brain tumor called glioblastoma multiforme. We are using it either before, during, or after their standard treatment of oral chemotherapy and radiation. During this time, many patients are on steroids, which have the very well-known side effect of raising blood sugar. Having 80 percent of calories coming from fat ensures that patients can achieve ketosis despite this side effect. Another reason being that most—but admittedly not all—patients with brain tumors have seizures. Fat provides 9 calories per gram and a steadier stream of energy, creating a less favorable environment in the brain to have a seizure. Lastly, if planned correctly, having most of this 80 percent fat coming from mono- and poly-unsaturated fatty acids (also known as omega-3s and omega-6s) can help reduce the cerebral edema these patients experience by reducing their inflammation.

Can the ketogenic diet be used for any type of cancer?

Despite this well-known theory being around for years now, the studies that have the most support for the ketogenic diet and cancer are mainly for brain tumors. Another recent study from Dr. Adrienne Scheck shows how the ketogenic diet sensitizes malignant cells to be killed and saves normal cells during chemotherapy and radiation. Another scientist, Thomas Seyfried, Ph.D., has been studying the ketogenic diet and its effects on epilepsy and brain tumors for over decades He's published over 20 articles on the subject, with the most recent case series published looking at a 38-year-old male with glioblastoma using the keto diet along with other metabolic therapies. His disease has been stable for three years now. The diet is also currently being investigated in endometrial cancer, breast cancer, prostate cancer, and other advanced cancers. That said, there is no evidence that supports using the ketogenic diet alone as a way to treat cancer. If the keto diet is used at all, it should be under the supervision of an oncologist and along with other science-backed cancer treatments.

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Is using the keto diet in cancer treatment safe?

As promising as this sounds, there are several considerations to think of before starting this diet if you have a cancer diagnosis and are actively in treatment. For instance, if you have a diagnosis of non-small-cell lung cancer; esophageal, pancreatic, or gastric cancer; or are undergoing a stem-cell transplant, your metabolism tends to be more altered and you burn calories much faster than you would with other cancer diagnoses. Pancreatic cancer and cancers of the bile duct and gallbladder tend to cause fat malabsorption and therefore may not benefit from a ketogenic diet.

It's also possible to have nutrition-impact side effects that may be hard to manage on the diet, such as diarrhea and nausea. Poor appetite and intake are also common during cancer treatment, and people who do not eat regularly, are prone to hypoglycemia, or are taking glucose-lowering medications such as metformin can experience low blood sugars. This effect is enhanced on the diet and can be very dangerous.

So what is the take-home on the keto diet and cancer? It's not quite cut and dried—and there are a lot of factors to consider. It's important to ask the right questions: Do you have a cancer diagnosis that might benefit from the keto diet, or is there currently research being done testing the keto diet on your type of cancer? Have you recently lost or gained weight unintentionally? Are you having side effects from your treatment that has affected your eating? Are you in survivorship? There are many individual factors to consider. I encourage anyone with cancer or who had cancer and is thinking about utilizing the ketogenic diet as an adjunct to their treatment plan to speak with their M.D. and R.D. about it. This isn't a diet you should do without medical supervision.

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