Keto Diet and Cancer

The ketogenic (keto) diet is a high-fat, low-carb eating plan that comes with a plethora of health claims, one of which is that it can help fight cancer. Such claims are nothing new. In fact, research back in the 1980s found that ketogenic diets were able to reduce tumor size and even wasting from cancer.  

Such studies have since sparked an interest in the ketogenic diet as a possible cancer therapy. Researchers are now exploring the potentials of keto diets in preventing and even curing cancer, especially when followed alongside more conventional cancer therapies like chemotherapy and surgery.

But is there much to hope for or is it better to stick to traditional therapies? While there may be a lot of talk about keto curing cancer, the reality is a bit more complicated. Learn more about the keto diet and its effects on cancer in the lines below.

What is the Keto Diet?

The keto diet is a very-low-carb and high-fat eating plan. The diet is different from other popular low-carb eating plans, including the famous Atkins diet. On the keto diet, 70-80 % of your calories must come from fat, while your carbohydrate intake is limited to roughly 50g per day. Eating in such an extreme way puts the body in a metabolic state called ketosis.

When you are in ketosis, your liver is metabolizing fat at a great rate in order to produce ketones – acidic molecules that replace glucose as fuel. Think of ketosis as your body’s emergency power system; when glucose levels run low, the body’s own fat stores serve as substrates for this new fuel, i.e. ketones.

This effect of the keto diet easily leads to weight loss, which has been confirmed through research. But keto was not originally designed to be a weight-loss diet. Doctors in the 1920s designed the diet to help treat epilepsy in children. Later on, the diet was found to be promising for diabetes management, other neurological conditions, PCOS, weight-loss, and, of course, cancer.

Keto Diet and Cancer

Going back to the 1920s, German scientist Otto Warburg found that cancer cells grow by metabolizing large amounts of glucose anaerobically (without oxygen). Dr.Warburg also believed that abnormal cell metabolism was the underlying cause of all cancers. Nowadays, we know that gene mutations cause cancer, and that abnormal cell metabolism of glucose is the result, rather than a cause, of cancer.

Because most cancer cells rely on an oxygen-free pathway, they need to use more glucose to produce the same amount of energy as healthy cells. Most glucose in the body comes from carbohydrates, which you restrict on a keto diet, but some circulating glucose is made from protein. Your body cannot convert fatty acids to glucose. Instead, it converts fat to ketones, a completely different fuel source. Animal studies found that cancer cells are unable to use ketones to make energy and to continue proliferating.

Studies in humans have also found positive results with glucose reduction and greater ketone levels. One particular study that involved 10 patients with incurable and advanced cancers found that insulin inhibitors helped slow-down disease progression. Insulin inhibitors are able to induce ketosis, acting in a similar way as a ketogenic diet.

And according to one systematic review of ketogenic diets as cancer therapies, there were case reports where the diet seemed to work to some extent. Two girls with advanced stage brain cancer had a 22% decrease in tumor SUV when these patients were on a keto diet. Another case of a 65-year-old woman also with brain cancer also found improvements after she was put on a calorie-restricted ketogenic diet.

What Is the Take on Keto as Cancer Therapy?

While the many studies in mice and the few studies in humans show promising results, there’s still a long road ahead before keto can be prescribed to cancer patients. Studies on keto and cancer are still preliminary, consisting of mostly of safety studies and case series. But, from what we do know, it seems that keto is safe to follow according to Tan-Shalaby Jocelyn, medical oncologist and Clinical Assistant Professor of Medicine at the University of Pittsburgh School of Medicine.

Dr. Tan-Shalaby also believes that it’s unlikely that long-term serious effects would be an issue when keto is used as cancer therapy. She also believes that, by itself, keto is not likely to be used as a primary therapy against cancer. Instead, it seems more promising as an adjuvant treatment. So, all in all, the ketogenic diet is a promising treatment for cancer, but more research is needed before we can know for sure.

Besides using keto to treat cancer, newer studies have also found that the diet may help with cancer or cancer-treatment side effects.  A study published in Nature found that ketogenic diets can help treat hyperglycemia (high blood glucose) in cancer patients taking cancer-fighting drugs known to cause this side effect. The same study found the keto diet may help boost the efficiency of these drugs and minimize other side effects.

What Cancer Patients Should Know

As already said, following the keto diet is unlikely to cure cancer alone. Instead, the diet may be a good adjuvant cancer therapy to go alongside surgery, chemotherapy, and radiation treatment. If you’re considering keto to treat cancer, always let your doctor know.

What you also need to keep in mind is that the keto diet is never easy to follow, and it becomes even harder when battling dangerous illnesses such as cancer. Weight loss is a common side effect of going keto and something you need to avoid when fighting cancer and if already underweight. Besides that, the ketogenic diet comes with other uncomfortable symptoms such as nausea, muscle cramps, and fatigue in the induction phase, and this can be difficult to manage when undergoing cancer treatment.

You also need to keep in mind that not all research found ketone bodies to have antitumor effects. Studies on breast cancer cells found that ketones may actually lead to faster tumor growth. This is known as the  β-OHB (a ketone body) paradox. This seems to be limited to breast cancer cells, though. But knowing that keto diets and the ketone bodies they generate are not a universal cancer cure.


Receiving a diagnosis of cancer is heart-wrenching, to say the least. Any talk of a promising new treatment can bring about a great deal of hope in those diagnosed with this disease. This has been true for the keto diet as well, which is now growing in popularity mostly for weight loss. However, when it comes to its effects on cancer, we know very little.

Studies are few and far between. Some studies also contradict the little we already know about the effects of keto on cancer. Until more conclusive evidence comes to light, it’s best to stick to proven cancer treatments. With today’s advancements in cancer research, we’re seeing more and more effective therapies boosting patients’ outcomes. Other approaches, such as following a keto diet, can prove to be helpful alternatives to go alongside more conventional approaches.

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