The ketogenic diet has seen its popularity steadily increase in the last decade due to being a diet regimen that is less restrictive compared to others. Thanks to its peculiar combination of macronutrients (mostly healthy fats and proteins) and the limitation of carbohydrate intake to less than 50 grams per day, the keto diet pushes the human body to switch from burning glucose, the leading energy source of the body, to burning fat. Besides being effective for weight loss, the ketogenic diet is now being used as a complementary treatment in cancer therapy.  The efficacy of the ketogenic diet in reducing tumour growth has been seen in a wide range of cancers in lab animals, including brain, prostate,pancreatic, and gastric cancer. It has also shown promise for the treatment of brain and ovarian cancer in humans.

What is the keto diet for cancer ?

While a standard keto diet for weight loss focuses on high fat and protein and restricting carbs to 20-50 grams per day, the ketogenic diet for cancer treatment restricts both carbs and protein. Reducing protein intake in cancer patients further restricts tumor growth and lowers mortality in humans. Because of the restrictive nature of the keto diet, it is contraindicated in patients with cachexia, a condition of extreme weight loss and muscle wasting common in cancer patients.  Always consult with a doctor to figure out the best diet for you.

How does the keto diet work in cancer? 

Here are a few mechanisms through which a keto diet fights cancer:

The keto diet starves cancer cells

Two recent scientific publications dwelled on how the keto diet can be used in combination with standard therapies like  surgery, chemotherapy, radiotherapy, and immunotherapy. The first, more plausible proposed mechanism, is that the tumour is forced into a situation of energy scarcity due to the glucose shortage that results from the reduction of carb intake. It would be difficult for cells to grow and proliferate without energy. Let’s make this clearer: I’m a cancer cell who needs carbs to break them down into glucose and derive energy. If the body in which I’m growing drastically reduces carb intake (following a ketogenic diet) I no longer have my daily source of glucose, I run out of energy and I am no longer able to grow. It seems that this effect reinforces the anti-tumour effects of cancer therapies and ameliorates patients’ quality of life.

The ketogenic diet  also reduces insulin levels, which are another essential factor for cancer cell proliferation. Insulin is considered a survival factor that triggers the cell’s inner mechanisms to grow and proliferate. With less circulating glucose, the body produces less insulin, tumour cells receive little or no survival input which reduces their growth or leads them to kill themselves through a process called apoptosis.

Tumor microenvironment, normal cells, molecules, and blood vessels that surround and feed a tumor cell. Microenvironment can affect how a tumor grows and spreads.
The ketogenic diet may make the molecular environment in your body less hospitable to cancer cells. Shown: The tumor microenvironment: normal cells, cancer cells, inflammatory cells, and the blood vessels that surround and feed tumor cells.

The keto diet creates unfavorable conditions for cancer

To further add power to the keto diet, there is a side effect that this regimen triggers in cancer cells: the production of free radicals. The lack of glucose supply puts the tumour cell under great pressure to survive, pushing mitochondria (the cell energy factories) beyond their limits, unpairing the cell’s inner metabolic mechanisms which are no longer able to properly function. Free radicals make the environment in cancer cells inhospitable, which makes the cells themselves even more vulnerable. There are some studies in animals that show that the  keto diet has been able to not only slow or suppress tumour growth but also extend lifespan, making cells more sensitive to chemotherapy and overcoming resistance to drug treatments.

The keto diet helps cut the oxygen supply to cancer cells

Another potential mechanism exerted by the ketogenic diet seems to be the reduction of vascularization, the amount of blood vessels in the tissues. Tumors need oxygen to grow and, since oxygen is carried around the body by blood, having a lot of blood vessels is fundamental. As a tumor grows, the cancer cells tend to create blood vessels from pre-existing ones through a process called angiogenesis. In mice affected by brain cancer, the keto diet reduced the tumor’s ability to build new vessels, limiting its growth. A thing that you should keep in mind is that cancer cells are less capable of deriving energy from ketone bodies (they prefer glucose) and this is far more difficult when the oxygen runs low due to few blood vessels.  A different study showed how ketone bodies released in the bloodstream during the keto diet have the potential to reverse altered cancer cell genetic profiles to restore a non-pathological one. This ability is one of the most difficult to explain. Long story short: the high amount of ketone bodies is able to influence enzymes that keep DNA stable and less susceptible to damages which would lead to the cell becoming cancerous.

Evidence of the keto diet for cancer treatment in humans

Most of the evidence on the ketogenic diet and cancer come from preliminary studies, mostly on animals, and there haven’t been exhaustive experiments on humans. However, 2 clinical trials have analyzed the influence of keto diet on women with ovarian cancer. They found that the keto diet can help cancer patients improve their quality of life, having more energy and an enhanced physical state. Additional positive actions exerted by the keto diet are: a general improvement of insulin levels (contrasting cancer mass growth) and a tumour environment less hospitable for cancer cells. Ketogenic diets might also delay tumor progression in humans with gliomas.

Despite all its incredible positives, the ketogenic diet does NOT replace the standard cancer therapies (surgery, chemotherapy, radiotherapy, immunotherapy); but it’s useful to reinforce their power. Restricting the possibilities of cancer cells to grow by depriving them of fuel stresses cancer cells and makes them more vulnerable to radiation and chemotherapy.