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Patient question

Can a diet cure your cancer?

Food and cancer

We often get questions from cancer patients who want to understand what they can do themselves to complement the treatment recommended by their medical team. During times when a lot feels uncertain, it can be helpful to take charge of aspects you can control, such as your diet. 

Anyone who has ever done a Google search on food and cancer, knows there is a tremendous amount of information available on nutrition, often promising that any cancer can be cured as long as you adhere strictly to a certain diet or take specific supplements. Unfortunately, it is often hard to tell science from fiction. So, if you have cancer and are considering a specific diet, please discuss it with your treating physician or an oncodietician first.

Common diets explored by My Cancer Navigator 

Mediterranean diet

This diet is characterised by a high consumption of fruits, vegetables, whole grains, legumes, nuts, olive oil, and moderate intake of fish and poultry. It is thought to have antioxidant and anti-inflammatory effects. Research has shown it not only reduces the risk of developing cancer (such as breast, prostate, and colorectal cancers), but also enhances quality of life and survival rates among existing cancer patients. This has been mostly studied in women with breast cancer, but there are studies suggesting similar results in colon and prostate cancer.  

The mediterranean diet is clearly beneficial for the prevention (or improvement) of other conditions, such as heart disease and diabetes, and for most people it is easy to stick to. Nonetheless, you should always consult with your doctor and dietician if this diet is right for you. 

Important note: despite the association of the mediterranean diet with wine, alcohol is not recommended. Alcohol can cause many health issues, and it has been classified a long time ago as a group 1 carcinogenic, which means it has been proven to increase the risk of many different cancers. 

Keto(genic) diet

A ketogenic diet, or keto diet, is a low-carb, high-fat eating plan that encourages your metabolism to switch from burning carbohydrates to fats, entering a state known as ketosis. This diet includes foods like meat, fish, eggs, and healthy oils, while avoiding sugary and high-carb foods, such as potatoes, bread, rice, and pasta.  

It is hypothesised to be effective against cancer by reducing the glucose that cancer cells need to grow, potentially slowing their growth and spread. But it is important to realise that your body will always ensure a minimum level of blood glucose, because your brain also relies on this as a source of energy. 

Although eliminating refined sugars and limiting starches is a healthy choice, a strict ketogenic diet can be quite difficult to maintain. It requires meticulous planning, shopping and cooking, and may affect life quality due to the dietary restrictions, or symptoms like nausea. As a result, it may be difficult to eat, so it could be a challenge to get all the calories you need. 

A keto diet can increase the risk of malnutrition, which could worsen your prognosis and, good to know: you can be overweight and still be malnourished, if you do not get all the important nutrients. 

Some studies in animals and small human trials suggest a ketogenic diet may enhance cancer treatments and improve quality of life. However, more research is needed to establish what, if any, the effect of a ketogenic diet might be, in which cancers, and in what stage of the disease.

If you wish to try this, make sure your doctor and dietician are ok with it, you can tolerate it, and avoid malnutrition and excessive weight loss. 

Intermittent fasting

This approach does not specify what you should eat, but rather when you can eat. There are different schedules: 

  • Eat during 8 of 24 hours only, where you can only consume food between 12noon and 8pm for instance.
  • Eat 5 days in the week and fast for 2 days (consecutive or not).
  • And specific to cancer patients on chemotherapy: do not eat, or only a small amount, in the days around your treatment. 

There is some preliminary evidence that intermittent fasting might have beneficial effects on health in general, by lowering insulin levels and reducing inflammation, it could reduce the risk of high blood pressure, diabetes, heart disease, and help with achieving a healthy weight. In cancer specifically, there are few studies in humans, and there is some indication that fasting might help with side effects from chemo. A clear effect on the cancer itself has not been conclusively demonstrated.

Here too are the same caveats as with the ketogenic diet: intermittent fasting might interfere with quality of life and increase the risk of malnutrition or excessive weight loss. Definitely speak with your doctor and dietician if you are considering this.

Fad diets

We use this term to describe diets, put forward by individuals or companies, that come with certain red flags, such as:

  • They include large amounts of certain foods and/or exclude specific types of food.
  • They are claimed to have extraordinary health benefits, often for many conditions.
  • They are associated with expensive courses, retreats, or equipment (like juicers).

Examples of this are the Brudzinski, Atkins and Moerman diets, as well as juice, “alkaline” or orthomolecular diets. These have generally not been shown to have a beneficial effect on cancer, and in some cases they can even be harmful. Pay attention to the warning signs mentioned here, and ask for professional guidance.

A word about supplements

Online and in real life, it is easy to find therapists, nutritionists, coaches who are happy to sell you their wisdom and products. Usually, they will run a large battery of obscure tests, establishing vague imbalances, deficits and organ dysfunction, which require urgent intervention. Beautiful surroundings and adjectives like holistic, molecular, personalised or naturopathic are meant to put patients at ease and appeal to many who feel unheard in the world of conventional medicine. Unfortunately, for most supplements there is no evidence that they are effective against cancer. If you do decide to take supplements, make sure to consult your oncologist or nurse if it is safe. 

(for a more extensive discussion on supplements please check out this previous blog) 

Now what? 

It is clear that, just as there are no miracle drugs, there are no miracle diets. However, there are dietary choices that can bolster your health overall and potentially your cancer treatment.  

At the very minimum, a healthy diet can make you fitter, and therefore more equipped to deal with difficult treatments. Whenever possible, combine a balanced diet with exercise and movement, maintain a healthy weight, and aim for stress reduction. A supportive social network is alsobeneficial.
 

Important takeaways: 
  • A diet cannot replace a cancer treatment.
  • Always speak with your physician and dietician if you are considering a diet or taking supplements.
  • Make sure your diet is balanced and you get all the nutrients you need.
  • Keep an eye on your weight.

For more tips on diet and lifestyle and cancer, please check out the website of the World Cancer Research Fund International. Their cancer prevention recommendations also apply to people with cancer.

Or do you have a specific question? We can help! Contact our free information service My Cancer Navigator 

Gabry Kuijten
author

Gabry Kuijten, MD, is the Coordinating Physician of My Cancer Navigator, the personal service for patients and doctors from the Anticancer Fund. Her passion is to support patients in their search for accurate, relevant and understandable information about their illness and treatment options, so they can make well informed decisions. Previously, she worked as an internal medicine specialist in the US, and in the pharmaceutical industry. She's also a copywriter for medical & health related topics and translates medical texts.