By Matt Paysour
After several long years of public humiliation, fat seems to be in a bit of a renaissance at the expense of the carbohydrate. Butter, bacon, and eggs are now not only allowed, but celebrated among many following ketogenic diets. (Because no, Lindsay Lohan, butter is, in fact, not “a carb”). Meanwhile, a growing storyline around the keto diet claims that it has specific clinical applications. Enough patients with cancer are now curious about the keto diet as an accompaniment—or even an alternative—to traditional radiation and chemotherapy that cancer treatment centers are addressing this question directly. So what does the keto diet do? And what is the rationale behind the “keto diet as cancer treatment” claim? And most importantly, has it actually worked as a cancer treatment?
The keto diet
Calories in our diets come from foods containing carbohydrates, fats, and proteins, called macronutrients. The United States Dietary Guidelines recommend a diet consist of about 45-65% of calories from carbohydrates, 20-35% of calories from fats, and 10-35% of calories from proteins. The ketogenic, or “keto,” diet is an extremely low-carbohydrate diet that drastically shifts the caloric breakdown of these three macronutrients. In the keto diet, carbohydrates account for just 5% of calories, protein accounts for about 15% of calories, and fat accounts for a staggering 80% of calories.
Normally, the human body generates energy through glucose (a simple sugar), which can actually be made from breakdown of any one of carbohydrates, proteins, or fats. However, in the ketogenic diet, the extremely low-carbohydrate intake helps the human body to mimic a fasting state, when glucose is less available to provide energy to the body. Because glucose availability is limited, the body shifts its metabolic priorities away from glucose production. In other words, the back-up generator is turned on, and we make something other than glucose for fuel.
And that back-up generator? Fats.
When on a proper ketogenic diet, the human body shifts to breaking down fats to produce ketone bodies, an alternative energy source that can be used to fuel the brain, muscles, and the heart. This state in which fats are being used to produce ketone bodies for energy is known as ketosis, and, at least in the short-term, has been shown as safe and sufficient for fueling the human body. (Fun fact: a by-product of ketone body production is acetone, more commonly known as nail polish remover. When someone on the keto diet enters ketosis, you might notice that their breath smells like acetone, even though they (hopefully) have not been consuming nail polish remover.) These ketone bodies are central to the argument for use of the keto diet in cancer treatment.
Rationale for use in cancer treatment
The keto diet has already been used in clinical settings for several years now. The keto diet actually owes its origin to the clinical setting, as it was originally developed in the 1920s as a treatment for pediatric patients with epilepsy. In fact, it is still currently used in epilepsy treatment, though its application is not limited just to this disorder. Many researchers have begun advocating for the keto diet to serve as a primary treatment option for patients with type 2 diabetes, and research in its potential effectiveness in treating polycystic ovary syndrome, acne, and Alzheimer’s—among many other disorders—is ongoing.
Speculation for effectiveness of the keto diet in cancer treatment specifically began not long after the diet’s inception in the 1920s. Later that decade, biochemist Otto Heinrich Warburg discovered that cancer cells depend heavily on glucose and glucose metabolism to survive, a Nobel Prize-winning discovery that came to be known as the Warburg Effect. Logic then dictates that a diet that favors the use of ketone bodies—instead of glucose—may effectively starve cancer cells of their primary fuel (glucose) while still providing fuel for the rest of the human body (ketone bodies).
The biggest question still remaining, then: does the keto diet work to treat cancer?
State of the evidence
Well, the answer is a resounding and authoritative “maybe” with echoes of “possibly sometimes, with a little help from other treatments.”
Our best evidence for its effectiveness comes from studies in mice, in which the ketogenic diet has been shown to slow tumor growth and prolong survival in pancreatic cancer, metastatic cancer, and malignant brain tumor models. However, each of these studies used the ketogenic diet with other forms of cancer treatment at the same time, which suggests that the ketogenic diet may be more effective as an additional therapeutic measure that works in concert with already-used methods.
In humans, the evidence is much more equivocal. There are instances of cancer cases that responded well to treatment with the keto diet in conjunction with the typical chemotherapy and radiation, and there are instances of cancer cases that hardly responded at all to the addition of the keto diet to the treatment regimen. In fact, some cancer cells have been shown to express “ketolytic enzymes,” meaning some cancer cells are not quite as reliant on glucose as initially thought, and are able to use ketone bodies for energy too.
Now, it should be noted here that “cancer” is an umbrella term capturing diseases of varied causes, stages, and diverse cell types. “Cancer” can simultaneously refer to a broad spectrum of complex diseases, but leukemia is not glioblastoma is not pancreatic cancer.
This means, in other words, that most cancer cases are different and will therefore respond differently to the keto diet. Sometimes it may help, sometimes it may not. Cancer is biologically and physiologically complicated. This, in addition to the small sample sizes in human studies, likely contributes to the inconsistency in research findings.
The literature ultimately presents a few major takeaways:
First, the ketogenic diet has not been evaluated in humans as a standalone cancer treatment in randomized controlled clinical trials. The American Institute for Cancer Research notes that “no major cancer health organizations recommend the ketogenic diet for cancer patients,” and thus, patients with cancer should not be advised to forego current cancer care practices and replace them with the keto diet alone.
Second, patients interested in the keto diet should first consult a physician and a registered dietitian. Because of the diet’s unusual macronutrient composition, the keto diet can be difficult to do well and to maintain. Registered dietitians play a vital role in implementing ketogenic diet protocols for patients with cancer, and can ensure both diet adherence and optimize patient nutrition while using the keto diet.
Third, much of the evidence in humans for the keto diet as an additional therapeutic option for patients with cancer comes from small-scale case studies. Larger-scale clinical trials may help to show in which cancer cases and cancer types the keto diet may be beneficial.
And fourth, cancer treatment is both physically and emotionally demanding, and diet is often a controllable factor that helps patients reassume agency in a situation where much agency has been stripped away. The keto diet has generally been shown to be well-tolerated, and in at least one trial, the keto diet improved patients’ emotional well-being and insomnia. The mechanism at work here is unclear. It may be that the keto diet provided some physiological benefit, as it has been hypothesized, for instance, that ketone bodies may induce a mild euphoria at the onset of the change in dietary habits. Another likely possibility is that the dietary changes increased patient involvement in their own treatment, thereby improving their emotional well-being by more psychological means. Regardless, while the physiological impact of the keto diet may or may not be beneficial for every patient with cancer, some patients may benefit from exploring the keto diet as an option anyway.
The bottom line is that the ketogenic diet, like all diets—and most medical treatments, for that matter—is not a singular silver bullet to solve any problem. But there is certainly promise and merit to its consideration in cancer treatment.
So maybe there is a little something to fat not being all bad?
Peer-reviewed by Allison Lacko