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 By now, you’ve probably heard of the ketogenic diet (AKA “keto”) and maybe you’ve even tried or thought about trying it. It is wildly popular right now, in all its various forms. But it is also controversial. A quick internet search will bring up a variety of opinions on the matter. Today on the blog, we are going to break down the ketogenic diet for people with cancer based on the evidence available to us.

** Spoiler Alert: There is not enough evidence in humans to recommend the ketogenic diet for cancer patients at this time **

What’s a ketone?

Just like a car needs gas to run, our bodies need fuel to run, too! We get this fuel from the food we eat (especially from foods that have carbohydrates). Our bodies turn this food into sugar, our favorite form of fuel. If we don’t eat food for a while, like when we are sleeping, our bodies will use and make its own sugar. If we don’t eat food for even longer, our bodies have a back-up system. This back-up system is ketones and they are made from breaking down fat. It is like running your generator during a power outage.

What is the ketogenic diet?

When we run on our ketone back-up system, we are using mostly fat for fuel. People who follow a ketogenic diet try to run on this back-up system all the time by consuming only a tiny amount of carbohydrates, and a lot of fat. This can trick our bodies into thinking we are starving, and ketones are made. Remember, when we use fat for fuel, we make ketones!

The ketogenic diet differs drastically from the way most people tend to eat. The average American eats about half their food in the form of carbohydrates. Someone on the ketogenic diet only eats 4-6% of their food as carbohydrates. For example, the average American who eats 2,000 calories per day will consume approximately 250 grams of carbs in a day. On the ketogenic diet, the same person can only eat 20-30 grams of carbohydrates. For example, half a bagel, a large apple, or a small potato each contain 20-30 grams of carbs. That would be it for the whole day! Because of this, foods high in carbohydrates like rice, pasta, and bread, as well as beans, fruits, and certain vegetables (think potatoes and corn) are eliminated on the ketogenic diet.

What does the ketogenic diet have to do with cancer?

Some cancer cells use sugar in a different way than normal, healthy cells. The ketogenic diet tries to take advantage of this altered metabolism. Theories are that the ketogenic diet might reduce the amount of fuel (sugar) that is available to cancer cells, slow their growth, or cause the cancer cells to make byproducts that will aid in their own destruction.1

Ok, let’s talk about sugar for a minute. Even if you cut out sugar, including carbohydrates, from your diet, your body will still make its own. Remember, sugar is your body’s favorite form of fuel. We cannot live without sugar in our blood. Just like ketones are a back-up mechanism during starvation, our bodies make their own sugar when we don’t eat enough carbohydrates. We make this sugar out of our muscle and fat. Having sugar in our blood is so important that our bodies do not even care where the muscle comes from. It could come from your arms, legs, or even your heart or lungs. Check out this resource to learn more.

In healthy cells, when we start to make ketones sugar production usually slows down, and this means less muscle is being used up. This is good news. But this is a survival mechanism for when we don’t have enough food. We don’t know if this same thing happens in cancer cells. Biological processes may be different in people with cancer.

Cancer cells also have wonky signals that tell them to keep growing. A complex cascade of growth signals occurs in healthy cells when we eat sugar or foods with carbohydrates. It is not clear if eating less carbohydrates affects those wonky growth signals in cancer cells or not. It is another thing we don’t know yet.

What is the evidence?

Studies have been controversial. Studies done in mice have shown that the ketogenic diet used with chemotherapy or radiation can boost the effectiveness of these treatments and improve results, like increased tumor shrinkage and survival 2-4 and might even protect healthy cells.1 Other studies with mice contradict these results, indicating that a ketogenic diet may not have any effect at all, or worse, might actually promote tumor growth.4

Experiments with mice are a great place to start to see if a treatment might work, but, as I’m sure you are aware, mice aren’t humans…

So, does the ketogenic diet help humans fight cancer?

So far, there have not been enough human studies to provide evidence that the ketogenic diet will help. There are currently two clinical trials with published results on that measured the effect of the diet on cancer. One study included recurrent glioblastomas,5 and the other included several different cancer sites (brain, liver, pancreas, lung, head and neck, thyroid, melanoma, biliary, kidney, and prostate-all of them were advanced cancers).6 Both of these studies ended up being too small to actually determine any effect. Each started with only around 20 people. One even had 76% of its participants drop out of its 16-week study because they couldn’t follow the diet that long.6 While these studies didn’t report any major adverse effects from the diet, almost all participants experienced weight loss5,6 (something we try to avoid while in treatment), and some even had increased triglycerides, altered electrolyte levels, and fatigue.6

Before a drug or treatment is approved for use it has to go through several levels of testing. The final level before approval includes thousands of participants. That is how we know if a treatment is safe and effective. And the ketogenic diet used in cancer patients is really no different. We want evidence that it is both safe and effective.

Well, what do we know?

We do have evidence that preventing unintended weight loss and staying hydrated during your cancer treatment can help you tolerate treatments and feel better.7,8 There is also lots of information supporting a plant-based diet and an active lifestyle for cancer prevention and survivorship. You can read more about these recommendations here. Eating plenty of plant foods, including whole grains, beans, lots of fruits and vegetables, lean protein, and less processed, fast foods helps to provide your body with cancer fighting nutrients. These are both safe and effective recommendations. So, go ahead-pile your plate with plants!

Guest blog post by Jessica Wallis, dietetic intern, MPH candidate in nutrition at UNC-CH, food lover, and future dietitian.


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  2. Klement RJ, Kämmerer U. Is there a role for carbohydrate restriction in the treatment and prevention of cancer? Nutrition & Metabolism. 2011;8:75. doi:10.1186/1743-7075-8-75.
  3. Poff, A. M., Ari, C., Arnold, P., Seyfried, T. N., & D’Agostino, D. P. Ketone supplementation decreases tumor cell viability and prolongs survival of mice with metastatic cancer. Int. J. Cancer. 2014;135(7), 1711–1720.
  4. Lv M, Zhu X, Wang H, Wang F, Guan W. Roles of Caloric Restriction, Ketogenic Diet and Intermittent Fasting during Initiation, Progression and Metastasis of Cancer in Animal Models: A Systematic Review and Meta-Analysis. Lluch GL, ed. PLoS ONE. 2014;9(12):e115147. doi:10.1371/journal.pone.0115147.
  5. Rieger J, Bahr O, Maurer GD, Hattingen E, Franz K, Brucker D, et al. ERGO: a pilot study of ketogenic diet in recurrent glioblastoma. Int J Oncol. 2014 Jun;44(6):1843–52.
  6. Tan-Shalaby JL, Carrick J, Edinger K, Genovese D, Liman AD, Passero VA, et al. Modified Atkins diet in advanced malignancies – Final results of a safety and feasibility trial within the Veterans Affairs Pittsburgh Healthcare System. Nutr Metab [Internet]. 2016;13(1):1–12. Available from:
  7. Arends J, Baracos V, Bertz H, Bozzetti F, Calder PC, Deutz NEP, et al. ESPEN expert group recommendations for action against cancer-related malnutrition. Clin Nutr. 2017; 36(5): 1187-1196 doi:
  8. American Cancer Institute. Benefits of Good Nutrition During Cancer Treatment.