Can a Ketogenic Diet Shrink Tumors or Stop Cancer? Is It Even a Healthy Nutritional Plan?


There’s been a great deal of promotional buzz on a ketogenic diet, but our continuing commitment at the Block Center is to investigate all questions/concerns so we can responsibly inform our patients. Therefore, we have evaluated the following:


A key question: Can a ketogenic diet help shrink tumors or stop cancer growth?


A few, small studies have suggested that the ketogenic diet might help slow the progression of certain cancers by inhibiting tumor growth. However, most experts believe that more research is required in order to more accurately evaluate the impact of a ketogenic diet on cancer and on the human body since many questions surround reported findings. For one, up to this point there have been very few controlled studies in humans with any standardized protocol for administering the diet.


Most of the studies showing positive results have been conducted on animals and are associated chiefly with brain tumors. Brain cells are unique in their ability to utilize ketones as a fuel source making glioblastomas — primary brain malignancies — one cancer where the ketogenic diet might have more impact.  For this reason, much of the research has been focused on this specific anatomical area.  However in these studies, dropout rates have been high due to the difficulty of this diet, and thus far the measurement of success is only a small increase in length of survival (days or maybe months).


One large, systematic, review from 2017 investigating the impact of ketogenic diet on tumor growth and survival time considered 268 studies on the topic and was only able to include 13 of those studies in the review.  All 13 of these studies were on animals, and the methods among each of the studies varied greatly with only 9 showing positive results.  Furthermore, the review points out that calorie restriction, and not necessarily a ketogenic diet, may be just as effective in reducing tumor growth.


Besides this question, there have been contradictory findings. One study conducted in 2010 by Michael Lisanti et al. found that epithelial cancer cells actually utilize ketones just as easily as glucose, fueling an approximate 2.5-fold increase in tumor growth, which is labeled the “reverse Warburg effect.”  But overall, there is a serious lack of well-designed, rigorous trials testing the validity of this diet in humans.  We definitely need research of longer duration and better-designed methods in order to nail down the true effects of the ketogenic diet on cancer and possible long-term side effects.


What is the theory behind the ketogenic diet?


During the 1920’s, Dr. Otto Warburg discovered that a common feature of all cancer cells is their ability to capture and metabolize large amounts of glucose then convert it to lactate, and this may indirectly promote tumor cell proliferation and growth. Known as “The Warburg Effect,” this phenomenon is the basis of the ketogenic diet, a high-fat, low-carbohydrate diet that is believed by some to inhibit tumor growth by creating a state of ketosis, potentially starving cancer cells of their essential fuel.


Specifically, the ketogenic diet consists primarily of foods high in fat, such as meat, eggs, processed meats, sausages, cheeses, butter, and oils, for example. Thus, this dietary approach requires drastically reducing all carbohydrate intake – unrefined as well as refined carbs – meaning it cuts out foods like whole grains, rice, beans, starchy vegetables, and fruits, all of which provide vital nutrients and essential fiber.


Problems and side effects of the ketogenic diet


One major concern of the ketogenic diet is that it is not only extremely difficult to maintain, but it may also cause severe muscle loss – a problem with medical consequences. Insulin helps build muscle, so if we remove carbohydrates from the diet, muscle glycogen stores become depleted.


Second, since the ketogenic diet is extremely low-carb, it eliminates fiber-rich grains, vegetables, and fruits, which could not only result in chronic constipation but, more significantly, lead to an increased risk of colon cancer and heart disease. Grain fiber is also used by gut bacteria to produce short-chain fatty acids, a major source of nutrition for cells in the gastrointestinal tract and key support for other critical functions, especially immunity. Depriving the digestive system of these essential, indigestible nutrients could have a negative impact on the body’s ability to fight cancer, infections, and parasites.


Third, since the ketogenic diet focuses on a high fat intake, this diet can contribute to an increased risk of hypercholesterolemia and hypertriglyceridemia – predisposing someone to serious cardiovascular disease. What is more — ketosis can contribute to fatigue, headaches, nausea, and poor performance status.


The Bottom Line


There simply is not enough evidence-based research at this time to support implementing a ketogenic diet (with exceptions in very special cases.) To reiterate — a diet high in animal fats and low in grains and fruits can increase inflammation and further weaken the immune system. Whereas, a diet that focuses primarily on plant-based foods that is high in fiber and phytochemicals and low in saturated fats such as whole unrefined grains, vegetables, fruits and legumes is protective against cancers (as well as other serious diseases including diabetes, heart disease, and stroke.) One additional point – in our dietary consults at the Block Center, we do remind patients to be mindful of individualized recommendations on portion sizes of whole grains and other carbohydrates, and that these are best accompanied by protein foods to help control blood sugar throughout the day.

(If you have further questions please call (847) 492-3040 so we, as Registered Dietitians at the Block Center, can address your concerns.)


By Katie Weir, RD, LDN and Liz Gold MS, RDN

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