There is no reliable evidence that a ketogenic diet can slow the growth of tumors in humans. There have been no good studies in patients with cancer that provide an answer to this question.
What is a Ketogenic Diet?
A ketogenic diet is a strict diet that consists of few carbohydrates, low protein and high fat.
Carbohydrates are starch (potatoes, bread, pasta, legumes), milk sugar (milk, buttermilk, yoghurt), fruit sugar (fruit, fruit juices), sugar (granulated sugar, cake and pastries) and grape sugar (syrup, honey, candy, soft drinks). These products may not be used or only to a very limited extent.
Another name for the ketogenic diet is also called as the low carb diet.
Important sources of protein are: meat, meat products, milk and milk products. Fats are not only found in butter, margarine, oil and frying and roasting products, but also in meat. For example; meat products, cheese, milk, dairy products, pastries and biscuits. In order to obtain sufficient fats for the ketogenic effect, it is usually also necessary to use a high-fat preparation throughout the day. Following a ketogenic diet is not easy. It differs greatly from the normal diet. Another thing that makes it difficult is to get the good ratio between fat, carbohydrates and protein every day.
What happens in the body with a ketogenic diet?
The goal of this diet is the formation of ketones. The body normally converts carbohydrates (starches and sugars) into glucose. Glucose is the fastest energy source for the body. Even it is the only energy source for the brain. In case of insufficient intake of carbohydrates, the body starts burning fat to get energy.
This fat burning leads to an increased amount of fatty acids in the blood. However, these fatty acids can not pass the barrier to the brain. That is why the liver from the fatty acids makes ketones, which can pass the barrier to the brain and serve as an energy source instead of glucose. Ketones are generally only formed in the body when less than 50 grams of carbohydrates are used per day.
The diet should also contain few proteins because protein counteracts the production of ketones. The ketogenic diet is used as a therapy with varying degrees of success in children and young adults with epilepsy to reduce or prevent epileptic seizures.
What is the theory behind the action of the ketogenic diet in cancer?
Like healthy cells, cancer cells need glucose for their energy. When the intake of carbohydrates is limited, the amount of glucose in the blood decreases. The theory is that a lack of glucose in the blood would ‘starve’ the tumor cells as it were.
A lower amount of insulin in the blood, which is due to a lower intake of carbohydrates, would delay tumor growth. Animal test research indeed showed that feed with a ketogenic composition can suppress the growth of tumors. Laboratory research with cancer cells further shows that the production of ketones seem to make the cancer cell more sensitive to radiotherapy and chemotherapy.
This theory is supported by animal studies in which the effect of radiotherapy was enhanced by a ketogenic diet and the survival was prolonged. But research in test tubes with cancer cells also shows that cancer cells adapt to the ketogenic diet. This was the thing how tumor cell turns into a more insensitive and malignant variant. This is confirmed by animal research.
In an experiment with mice, the tumor initially grew less hard in the group that received the ketogenic feed. But afterwards, the tumor grew faster and the growth in the ketogenic group even exceeded the growth in the group that received normal feed. In these studies, the ketogenic diet appears to work less favorably in the long term.
Research into the effect of a ketogenic diet in patients with cancer
No study has been done where patients following a ketogenic diet were compared with a non-diet control group. In a very small study in 16 patients with advanced cancer, for which no treatment was possible, a ketogenic diet was attempted for 3 months. But only 5 patients could maintain it. Hence, the effect was unclear. To get more clarity about the effect of the ketogenic diet, there are several studies in humans.
The effect of a ketogenic diet on brain tumors, during chemotherapy in combination with radiation in patients with pancreatic cancer and lung cancer and in patients with an advanced stage of cancer is investigated.
Is following a ketogenic diet safe for patients with cancer?
That’s not sure. When cancer cells indeed adapt to a ketogenic diet and change into a more insensitive and malignant variant, the ketogenic diet is not safe. A ketogenic diet is generally well tolerated with minimal side effects. Side effects that can occur are constipation, fatigue, salt loss and excess acidity in the blood (mild acidosis). In advanced cancer, a strict diet can work unfavorably if it is precisely the foods that are eaten from the menu that are deleted.
Never start a ketogenic diet yourself, but always consult with your doctor or dietitian.